R8124B MJTW01

MJTW01

Voice Intertripping Equipment

Service Manual

R8124B

MJTW01 R8124SERVICE MANUAL CONTENTS

CHAPTER 1 INTRODUCTION

CHAPTER 2 APPLICATION NOTES

CHAPTER 3 INSTALLATION AND HANDLING

CHAPTER 4 HARDWARE DESCRIPTION

CHAPTER 5 MODEM (Service manual R5927 included)

CHAPTER 6 FUNCTIONAL DESCRIPTION

CHAPTER 7 SOFTWARE DESCRIPTION

CHAPTER 8 OPERATING INSTRUCTIONS

CHAPTER 9 COMMISSIONING INSTRUCTIONS

CHAPTER 10 FAULT FINDING INSTRUCTIONS

ADDENDUM

CONTENT

1. SAFETY SECTION 3

1.1 Health and safety 3

1.2 Explanation of symbols and labels 3

2. INSTALLING, COMMISSIONING AND SERVICING 3

3. EQUIPMENT OPERATING CONDITIONS 4

3.1 Current transformer circuits 4

3.2 External resistors 4

3.3 Battery replacement 4

3.4 Insulation and dielectric strength testing 4

3.5 Insertion of modules and pcb cards 4

3.6 Fibre optic communication 5

4. OLDER PRODUCTS 5

5. DECOMMISSIONING AND DISPOSAL 5

6. TECHNICAL SPECIFICATIONS 6

1. SAFETY SECTION

This Safety Section should be read before commencing any work on the equipment.

1.1 Health and safety

The information in the Safety Section of the product documentation is intended to ensure that products are properly installed and handled in order to maintain them in a safe condition. It is assumed that everyone who will be associated with the equipment will be familiar with the contents of the Safety Section.

1.2 Explanation of symbols and labels

The meaning of symbols and labels may be used on the equipment or in the product documentation, is given below.

Caution: refer to product documentation Caution: risk of electric shock

Protective/safety *earth terminal Functional *earth terminal

Note: This symbol may also be used for a protective/safety earth terminal if that terminal is part of a terminal block or sub-assembly e.g. power supply.

*NOTE: THE TERM EARTH USED THROUGHOUT THE PRODUCT DOCUMENTATION IS THE

DIRECT EQUIVALENT OF THE NORTH AMERICAN TERM GROUND.

2. INSTALLING, COMMISSIONING AND SERVICING

Equipment connections

Personnel undertaking installation, commissioning or servicing work on this equipment should be aware of the correct working procedures to ensure safety. The product documentation should be consulted before installing, commissioning or servicing the equipment.

Terminals exposed during installation, commissioning and maintenance may present a hazardous voltage unless the equipment is electrically isolated.

If there is unlocked access to the rear of the equipment, care should be taken by all personnel to avoid electrical shock or energy hazards.

Voltage and current connections should be made using insulated crimp terminations to ensure that terminal block insulation requirements are maintained for safety. To ensure that wires are correctly terminated, the correct crimp terminal and tool for the wire size should be used.

Before energising the equipment it must be earthed using the protective earth terminal, or the appropriate termination of the supply plug in the case of plug connected equipment. Omitting or disconnecting the equipment earth may cause a safety hazard.

The recommended minimum earth wire size is 2.5mm2, unless otherwise stated in the technical data section of the product documentation.

Before energising the equipment, the following should be checked:

− Voltage rating and polarity;

− CT circuit rating and integrity of connections;

− Protective fuse rating;

− Integrity of earth connection (where applicable)

− Remove front plate plastic film protection

− Remove insulating strip from battery compartment

3. EQUIPMENT OPERATING CONDITIONS

The equipment should be operated within the specified electrical and environmental limits.

3.1 Current transformer circuits

Do not open the secondary circuit of a live CT since the high level voltage produced may be lethal to personnel and could damage insulation.

3.2 External resistors

Where external resistors are fitted to relays, these may present a risk of electric shock or burns, if touched.

3.3 Battery replacement

Where internal batteries are fitted they should be replaced with the recommended type and be installed with the correct polarity, to avoid possible damage to the equipment.

3.4 Insulation and dielectric strength testing

Insulation testing may leave capacitors charged up to a hazardous voltage. At the end of each part of the test, the voltage should be gradually reduced to zero, to discharge capacitors, before the test leads are disconnected.

3.5 Insertion of modules and pcb cards

These must not be inserted into or withdrawn from equipment whist it is energised since this may result in damage.

3.6 Fibre optic communication

Where fibre optic communication devices are fitted, these should not be viewed directly. Optical power meters should be used to determine the operation or signal level of the device.

4. OLDER PRODUCTS

Electrical adjustments

Equipments which require direct physical adjustments to their operating mechanism to change current or voltage settings, should have the electrical power removed before making the change, to avoid any risk of electrical shock.

Mechanical adjustments

The electrical power to the relay contacts should be removed before checking any mechanical settings, to avoid any risk of electric shock.

Draw out case relays

Removal of the cover on equipment incorporating electromechanical operating elements, may expose hazardous live parts such as relay contacts.

Insertion and withdrawal of extender cards

When using an extender card, this should not be inserted or withdrawn from the equipment whilst it is energised. This is to avoid possible shock or damage hazards. Hazardous live voltages may be accessible on the extender card.

Insertion and withdrawal of heavy current test plugs

When using a heavy current test plug, CT shorting links must be in place before insertion or removal, to avoid potentially lethal voltages.

5. DECOMMISSIONING AND DISPOSAL

Decommissioning: The auxiliary supply circuit in the relay may include capacitors across the supply or to earth. To avoid electric shock or energy hazards, after completely isolating the supplies to the relay (both poles of any dc supply), the capacitors should be safely discharged via the external terminals prior to decommissioning.

Disposal: It is recommended that incineration and disposal to water courses is avoided. The product should be disposed of in a safe manner. Any products containing batteries should have them removed before disposal, taking precautions to avoid short circuits. Particular regulations within the country of operation, may apply to the disposal of lithium batteries.

6. TECHNICAL SPECIFICATIONS

Protective fuse rating

The recommended maximum rating of the external protective fuse for this equipment is 16A, Red Spot type or equivalent, unless otherwise stated in the technical data section of the product documentation.

Insulation class: IEC 601010-1 : 1990/A2 : 2001 Class I EN 61010-1: 2001 Class I

This equipment requires a protective (safety) earth connection to ensure user safety.

Insulation Category (Overvoltage):

IEC 601010-1 : 1990/A2 : 1995 Category III EN 61010-1: 2001 Category III

Distribution level, fixed insulation. Equipment in this category is qualification tested at 5kV peak, 1.2/50µs, 500Ω, 0.5J, between all supply circuits and earth and also between independent circuits.

Environment: IEC 601010-1 : 1990/A2 : 1995 Pollution degree 2

EN 61010-1: 2001 Pollution degree 2

Compliance is demonstrated by reference to generic safety standards.

Product Safety:

72/23/EEC

EN 61010-1: 2001 EN 60950-1: 2002

Compliance with the European Commission Low Voltage Directive.

Compliance is demonstrated by reference to generic safety standards.

MJTW01 R8124SERVICE MANUAL

CHAPTER 1

INTRODUCTION

MJTW01 R8124SERVICE MANUAL Chapter 1

Page 1 of 2

Section 1. INTRODUCTION AND APPROVALS

1.1 Introduction

The MJTW 01 is a voice frequency high-security bi-directional intertrippingequipment which provides two independent protection signalling commands over asingle telecommunications link.

Intertripping, also known as transfer tripping, is the controlled tripping of a circuitbreaker so as to complete the isolation of a circuit or piece of apparatus. It isinitiated from protection at a remote location to effect local tripping independent ofthe state of the local protection. The MJTW 01 is used in a two-point scheme toeffect the tripping of remote circuit breakers and to disconnect faulty transformers,generators, reactors, capacitors, and other main plant from remote current infeeds,and to relieve abnormal system loading conditions.

A flexible design together with a choice of modem signalling speeds allows theequipment to be configured to meet industry requirements for intertripping timesranging between 25ms and 100ms.

The MJTW01 is fully compatible with existing AREVA T&D 'Teleprotection'equipment, and may be used as a direct replacement of such.

1.2 Approvals

1.2.1 British Approvals Board for Telecommunications (BABT)

The MODEM has approval for operation on British Telecom or other licensedprivate wire services for the channels as defined in Publication R-5927 inChapter 5 of this manual.

Approval No. NS/1423/2/M/602104.

MJTW01 R8124ASERVICE MANUAL Chapter 1

Page 2 of 2

Section 2. RELAY IDENTIFICATION

2.1 Model breakdown

MJTW01 S5 0001 A

Design suffix

Sequential number

Case: S5 rack mounted

Intertripping relay

Modular relay

2.2 Modem identification

BA0226 026 600 Baud channel 1BA0226 027 600 Baud channel 2BA0226 028 1200 Baud

Note : These numbers vary slightly from those identification numbers given for themodem in Chapter 5. This is because the modem publication has assumedvertical mounting of the modem and thus the modem front lettering isdifferent in the publication to how it appears on the MJTW01 relay. Thenumbers given here are the correct ones for the modem in the MJTW01equipment.

2.3 Controller module identification

BA0282 001 low voltage power supply, low voltage opto-isolated inputsBA0282 002 high voltage power supply, high voltage opto-isolated inputsBA0282 003 low voltage power supply, high voltage opto-isolated inputsBA0282 004 high voltage power supply, low voltage opto-isolated inputswhere

low voltage power supply, Vx1 is 24/54V i.e. 19.5 – 65.0Vhigh voltage power supply, Vx1 is 110/250V i.e. 87.5 – 300.0Vlow voltage opto-isolated inputs, Vx2 is 24/54V i.e. 19.5 – 65.0Vhigh voltage opto-isolated inputs, Vx2 is 110/125V i.e. 87.5 – 150.0V


CHAPTER 2

APPLICATION NOTES


Page 1 of 13

Section 1. INTRODUCTION

This section deals with the application of the MJTW01 intertripping relay, someexamples of which are illustrated. The settings of the relay are explained and theutilisation of the opto-isolated inputs and the output contacts is described. Theisolation requirements for British Telecom, or privately owned, circuits are alsogiven.

Section 2. INTERTRIP SCHEMES

The following schemes are just a few typical examples of how the MJTW01intertripping relay might be applied in practice. In each case it is assumed that theintertripping scheme is such that the protective relay at one end will be connected tothe trip inputs (see Section 5 in this Chapter) of the MJTW01 intertripping relay.The intertripping relay sends messages via the voice frequency communications linkto the MJTW01 at the receiving end of the link. If the second MJTW01 relayreceives a trip message, it operates its trip output contacts (see Section 6 in thischapter) and causes the circuit breaker at the remote end to which it is connected tooperate.

2.1. Internal transformer fault

When a power transformer develops an internal fault which does not draw anappreciable current through its terminals, this will be detected by the localdifferential protection for the transformer but it will not be seen by the remote end ofthe feeder. The differential protection sends a signal to the circuit breaker at theremote end via the MJTW01 intertrip relay. See Figure 1.

2.2. Transformer tee-off

Intertripping can be applied to the transformer tee-off scheme shown in Figure 2.When a fault is detected in the transformer, two intertripping signals are sent to eachof the circuit breakers on the transmission line. Once these breakers are open, theisolator can be opened, which effectively removes the transformer from the circuit.Auto-reclose relays can then be used to close the circuit breakers on the transmissionline, which allows normal transmission to continue without the distribution circuit.

2.3. Fault between the line transformer and the circuit breaker

When current transformers are only located on the feeder side of a circuit breaker, asshown in Figure 3, a fault between the transformer and the circuit breaker willoperate just the busbar protection. However the fault will not be cleared unless anintertrip signal to the remote end is sent, as the line protection cannot see the fault.


Page 2 of 13

Section 3. MODES OF OPERATION

The equipment can be user configured to work in either one of two modes. Mode 1uses an extremely secure coding method and is fully compatible with existing AREVAT&D 'Teleprotection' equipment. Mode 2 makes use of a coding method featuring a reduced message length, which is very dependable and achieves faster operate times. The details of the message formats in modes 1 and 2 are given in Chapter 6, Sections 2.6.1 and 2.6.2.


Page 3 of 13


Page 4 of 13

Section 4. SETTINGS

The settings for the MJTW01 relay are divided into two groups, namely code andfunction. These will be explained in detail in the following sections and the defaultsettings listed.

4.1. Code settings

These settings represent the messages sent and received by the intertrip relay. Theyare bit patterns which are turned into voice frequency patterns via the modem (seeChapter 6 Section 2.2) and signalled across the communications link. There are 7code settings and they vary slightly according to whether the equipment is in mode 1or 2, and they are as follows:

(The default settings are given in Section 3.2.2, Chapter 9).

IndexCode

DescriptionMode 1

DescriptionMode 2

C1 Equipment mode of operation

This can be mode '1' OR '2',depending on the userrequirements.

Equipment mode ofoperation


C2 Transmit channel ID code -

The identification code istransmitted first as part of thewhole message. There are 22channel ID codes, including 7test codes. The same choice ofcodes are given in both thetransmit and receive codes.

Transmit monitor code -

In mode 2, the message beingtransmitted on any onechannel is either a trip codeor a 'no trip' code ie. amonitor code.There are 20monitor codes. These are thesame in both transmit andreceive codes.

C3 Receive channel ID code -

At the receiving end this ID ischecked and validated. There arethe same number of receivecodes as transmit codes.

Receive monitor code -

In mode 2, the message beingreceived on any one channelis either a trip code or a 'notrip' code ie. monitorcode.


Page 5 of 13

C4 Transmit trip 1 code -

There are 15 different transmittrip 1 codes. The user selectedcode is transmitted along withthe channel ID when the relaysees a trip 1 input. This selectedcode must be the same as thereceive trip 1 code in the secondrelay. If there are no trips beingcommunicated, an all zerospattern is transmitted in the tripfield.

Transmit trip 1 code -

There are 20 differenttransmit trip 1 codes. If a trip1 input is seen, the userselected code is transmitted.This selected code must bethe same as the receive trip 1code in the second relay. Ifthere are no trips beingcommunicated, a monitorcode will be sent instead.

C5 Receive trip 1 code -

The trip 1 code received from thefirst intertrip relay is checkedagainst this code. It must be thesame as the transmit trip 1 codein the first intertrip relay, if thetrip is to be asserted.

Receive trip 1 code -

The trip 1 code received fromthe first intertrip relay ischecked against this code. Itmust be the same as thetransmit trip 1 code in thefirst intertrip relay, if the tripis to be asserted.










Page 6 of 13

4.2. Message format for mode 1

In mode 1, the message format includes 2 start bits or synchronisation bits, theidentification channel code (4 bits), the trip 1 message (5 bits) and trip 2 message (5bits). The last 8 bits are the parity check and these are calculated after 16 bits havebeen counted.

The trip codes start with a marker which is 1 if there is a trip and 0 otherwise.

This leaves four bits for the trip codes. In the idling state when no trip data is beingtransmitted, the channel identity is transmitted and the trip 1 and trip 2 patterns areboth 00000.

Four variable bits in each of the fields, channel identifier, trip 1, and trip 2, allows amaximum of fifteen channel identifier codes and fifteen trip codes for each tripinput. These codes are binary representations of the numbers 1 to 15.

When the remote loop testing feature is required, the channel identifiers are arrangedas seven pairs with one bit of the identifier being used as an odd/even marker for testor normal modes. The following only holds when a special test code has beenselected for the channel identifier field pattern i.e. '1t' to '7t'. The test marker is thenthe least significant bit of the channel ID code, and can be used to switch from theeven to the odd address codes. For example, address code '1t' is equivalent toaddress code '2' (0010) when the test input is not energised, but address code '3'(0011) will be transmitted when the test input is energised.

4.3. Message format for mode 2

The message format for mode 2 is completely different to that of mode 1. There areonly 15 bits per message as there is no parity check at the end. As well as this, themessage is not Manchester Encoded. It has instead, 4 synchronisation bits dictatingthe message start, three 0's and a 1. This is followed by a 1 for a monitor code and a0 for a trip code. Then there are 10 bits devoted to one of three messages: monitor(no trip), trip 1, or trip 2.

This simple format allows for a simpler message processing than in the previousmode. A list of all the possible monitor and trip codes are given as follows :


Page 7 of 13

4.3.1. Message codes for mode 2

Codenumber

Monitor codes Trip codes

1 0 0 0 1 1 0 1 1 1 0 0 1 1 1 0 0 0 0 1 0 1 0 1 0 1 1 0 0 0 02 0 0 0 1 1 1 0 1 1 1 1 0 1 0 1 0 0 0 1 0 1 0 0 1 0 0 1 1 0 03 0 0 0 1 1 0 1 1 1 0 1 1 0 1 0 0 0 0 1 0 1 0 0 1 0 1 1 0 0 04 0 0 0 1 1 1 1 1 0 1 0 0 0 1 1 0 0 0 1 0 1 0 0 0 1 0 0 1 0 15 0 0 0 1 1 1 0 1 1 0 1 0 1 1 0 0 0 0 1 0 1 0 1 0 1 0 1 0 0 06 0 0 0 1 1 1 0 1 1 1 1 1 0 0 1 0 0 0 1 0 1 0 0 0 0 1 0 1 0 17 0 0 0 1 1 1 0 1 1 1 0 1 1 0 1 0 0 0 1 0 1 0 0 1 0 0 1 0 1 08 0 0 0 1 1 1 1 1 0 1 1 0 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 19 0 0 0 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0 1 1 010 0 0 0 1 1 1 1 1 0 1 0 1 0 1 1 0 0 0 1 0 1 0 0 1 1 0 0 1 0 011 0 0 0 1 1 1 1 1 0 0 1 1 1 1 0 0 0 0 1 0 0 1 0 0 1 0 1 0 1 012 0 0 0 1 1 1 1 1 0 1 0 1 1 0 1 0 0 0 1 0 0 1 0 0 1 1 0 0 1 113 0 0 0 1 1 1 1 1 0 0 0 1 1 1 1 0 0 0 1 0 0 1 0 0 1 0 0 1 0 114 0 0 0 1 1 1 1 0 1 0 0 1 1 1 1 0 0 0 1 0 0 1 0 1 0 1 1 0 0 015 0 0 0 1 1 1 1 1 1 1 0 1 0 0 1 0 0 0 1 0 0 1 0 0 1 0 0 1 1 016 0 0 0 1 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 0 1 0 0 1 0 1 0 0 117 0 0 0 1 1 1 1 1 1 1 1 0 0 1 1 0 0 0 1 0 1 0 1 0 0 1 0 1 1 018 0 0 0 1 1 1 1 1 0 0 1 1 0 1 1 0 0 0 1 0 0 1 0 0 1 1 0 1 0 119 0 0 0 1 1 1 1 1 0 1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 1 120 0 0 0 1 1 1 1 1 0 1 0 0 1 1 1 0 0 0 1 0 0 1 0 0 1 0 1 1 0 0


Page 8 of 13

4.4. Function settings

There are five function settings and they are the same for both modes 1 and 2.

IndexCode

DescriptionMODE 1 and MODE 2

F1 Minimum trip output contact closure time -

This is the minimum time for which the trip output contactswill remain closed once a trip command has beenreceived.Values from 0.1 to 0.4 seconds can be selected insteps of 0.1 seconds.

F2 Action of trip 1 output contacts under communication failureconditions -

If a communications failure condition occurs during a trip, theaction of the trip outputs can be user programmed to hold thetrip output contacts as they are, or to reset them to theirnormally open state.

F3 Action of trip 2 output contacts under communication failureconditions -

Same as F2, but acting on trip 2 instead.

F4 Minimum communications failure alarm output contactclosure time -

This is the minimum time for which the communicationoutput contacts will remain closed, once a communicationfailure has occurred. Values from 0.1 to 0.4 seconds can beselected in steps of 0.1 seconds.

F5 Communication failure output contacts reset time -

This is the time delay between the recognition of the re-establishment of the communication link, and the clearance ofthe communication alarm output contacts. Values from 0.1 to0.4 seconds can be selected in steps of 0.1 seconds.


Page 9 of 13


Page 10 of 13

Section 5. EQUIPMENT VARIANTS AND TRANSMISSION TIMES

5.1. Modem

When ordering the equipment, one of two Baud rates may be chosen for the modemas detailed in the following table. The 600 Baud option has two different channels,one of which is chosen when ordering the equipment.

Transmission rates (Baud) Frequency options (Hz) Bandwidth (Hz)

600 ch 1 1500 +/- 200ch 2 2500 +/-200

1100 - 19002100 - 2900

1200 1700 +/- 400 900 - 2500

5.2. Auxiliary voltage supply

When ordering the equipment, one of two voltage ranges either high or low, may bechosen for the controller module as detailed in the following table. The range of thehigh voltage module is different for the power supply and the other inputs. There arefour variants in total as given in Chapter 1 Section 2.

Module ratings Nominal range(Volts)

Operative range(Volts)

Low voltage (all inputs) 24/54 19.5 - 65.0

High voltage (trip 1, trip 2, andtest inputs)

110/125 87.5 - 150.0

High voltage (power supply) 110/250 87.5 - 300.0

So the intertripping relay consists of one module which requires either a highvoltage or a low voltage power supply and a high voltage or a low voltage opto-isolated inputs supply, and one modem which is either 600 Baud with one of twochannels selected, or a 1200 Baud modem.

5.3. Transmission times

The transmission time of a teleprotection command, is the time elapsed between themoment of change of state at the transmitter input and the moment of thecorresponding change of state at the receiver output excluding propagation time.

The baud rate, mode of operation, and number of trips being sent in the case ofmode 2, will all affect the transmission time.

The maximum trip times (excluding the propagation delay time) are tabled below.


Page 11 of 13

5.3.1. Mode 1

Trip type Time (ms) Baud rate

Single trip 100 600

Two simultaneous trips 100 600

Single trip 55 1200


5.3.2. Mode 2


Single trip 45 600

Two simultaneous trips 45 for the firsttrip and 70 for

the second

600

Single trip 25 1200

Two simultaneous trips 25 for the firsttrip and 40 for

the second

1200


Page 12 of 13

Section 6. INPUTS

There are two standard rear MIDOS connectors at the back of the relay. There arefour inputs, one for the auxiliary power supply and three optically isolated inputs forinitiating test and trip commands and these are numbered as seen on the externalconnection diagram, Chapter 11. The controller module consists of four variants, asgiven in Chapter 1, Section 2 on relay identification, and care must be taken not toexceed the module's voltage range. All input and output circuitry is provided with2.5kV isolation.

6.1. Power supply input

This is capable of working with a range of dc battery supplies and there is a choiceof two nominal voltages, either 24/54 V or 110/250 V, depending on whether theequipment requires a low voltage or a high voltage power supply, see Section 4.2.The maximum burden on the auxiliary power supply is 6W.

6.2. Trip 1 input

This opto-isolated input needs a dc supply, but this time the choice of nominalvoltages is 24/54 or 110/125 V. Again the chosen voltage range depends on whetherthe equipment contains a low voltage or a high voltage module. A 220/250 inputvoltage rating may, however, be achieved by the use of external dropper resistors.Contact AREVA T&D for suitable values and ratings. This input initiates the transfer of a trip 1 command. The energised signalinput causes a message containing a trip 1 code to be transmitted to the intertrippingrelay at the far end. This is outlined in the examples in Section 2 above. In mode 2only the trip signal is boosted by 3dB. The burden of each of the inputs is 2 Watts atmaximum nominal rated voltage.

6.3. Trip 2 input

This opto-isolated input needs a dc supply, but as in the case of trip 1, the choice ofnominal voltages is 24/54 or 110/125 V. Again the chosen voltage range depends onwhether the equipment contains a low voltage or a high voltage module. A 220/250input voltage rating may, however, be achieved by the use of external dropperresistors. Contact AREVA T&D for suitable values and ratings. This input initiates the transfer of a trip 1 command. This energised signal input causes a trip 2 message to be transmitted to the intertripping relay at the far end. This is outlined in the examples in Section 2 above. In mode 2 only, the trip signal is boosted by 3dB. The burden of each of the inputs is 2 Watts at maximum nominal rated voltage.

Note: In mode 2, if the two trip inputs are energised simultaneously, the secondtrip message is sent immediately after the first and the operate time isincreased to 1.667 times the first trip time. If this event occurs in mode 1,both trip codes are sent in the same message and consequently both tripsare transferred in the normal operate time.


Page 13 of 13

6.4. Test input

NB This input signal will only be valid when the equipment is in mode 1, as thetest facility in mode 2 is completely different.

If a test is required, the user may energise this opto-isolated input by using theappropriate voltage supply. The test signal will be ignored unless a test code hasbeen programmed into the transmit I.D. code. This simply means the relay isenabled to perform a test if it is required to do so. An energised test signal will causea test message to be sent to the intertripping relay at the remote end. Any tripsreceived or trip inputs energised, while a test is under way, will be dealt with in thenormal fashion.


Page 14 of 13

Section 7. OUTPUT CONTACTS

There are four pairs of normally open trip 1 output contacts, four pairs of normallyopen trip 2 output contacts, and two pairs of normally open test contacts. There aretwo pairs of normally open communication failure contacts and one pair of normallyclosed scheme fault contacts. These output contacts must be wired according to theexternal connection connection diagram Chapter 11 and/or the scheme diagram.

7.1. Trip 1 output

If the MJTW01 relay receives a message containing trip 1 codes via itscommunication link from the MJTW01 at the other end, it closes its trip 1 outputcontacts.

7.2. Trip 2 output


7.3. Test output

The control of the test output varies according to whether the relay is configured foroperation in mode 1 or mode 2.

7.3.1 Mode 1:

If the MJTW01 relay receives a message containing a test marker via itscommunication link from the MJTW01 at the other end, it closes its test outputcontacts and the test led illuminates, only if its receive ID code is programmed witha test code. The test message is not reflected back to the other relay, unless the userchooses to wire the test output back into the test input and send a test message backin that manner. This has a flexible application and can be used for the transfer of anextra command if required.

7.3.2 Mode 2:

If the test key is pressed in this mode of operation, the local relay closes its testcontacts and its test led illuminates. Any trip will be received as normal but a tripinput at this stage will be ignored. The relay will transmit the expected receive codeinstead of the normal transmit code while the test is in progress. This allows acommunications loopback to be applied for fault finding on the communicationslink.

7.4. Communication failure output

If the MJTW01 relay receives a message via its communications link from theMJTW01 at the other end, which it does not recognise, or it receives no messages atall, the communications failure output contact will close after a user-programmable(function setting 5, F5) length of time.


Page 15 of 13

7.5. Scheme fault output

This is a normally closed contact which is held open throughout the operation of theequipment and closes in the event of a communications failure, a software or aprocessor failure, loss of supply, or invocation of the operator interface.


Page 16 of 13

Section 8. ISOLATION TRANSFORMER REQUIREMENTS

When the MJTW01 is to be used on British Telecom telephone circuits, or privatelyowned circuits, there is a requirement for a 15kV isolation transformer. This isconnected between the relay and the circuit, in order to provide circuit isolation.


Page 17 of 13

Section 9. CONNECTION OF THE MJTW01 INTERTRIPPING RELAYWITH A 'TELEPROTECTION' INTERTRIPPING RELAY

N.B. The MJTW01 relay can only be used with the Teleprotection relay when itis configured in mode '1' ie. C1 must be 1 (see Section 3 on code settingsabove).

In this mode, the two relays are perfectly compatible with one another. Each relayhas the same choice of codes for transmit and receive codes. When setting up theequipment ensure that the transmit code for the unit at one end is identical to thereceive code of the unit at the other end. Check that the baud rate and channel of themodems at each end is the same. The two relays are connected as normal with avoice frequency communications link.


CHAPTER 3

INSTALLATION AND HANDLING

MJTW 01 R 8124SERVICE MANUAL Chapter 3

Page 1 of 2

Section 1. INSTALLATION AND HANDLING

1.1 Receiving

Remove the relay from its container and inspect for obvious damage. If damage hasbeen sustained in transit, a claim should be made immediately to the transportcompany and a report sent to the nearest AREVA T&D office or agent.

1.2 Handling

The relay in its case is extremely robust and no special precautions are necessary.However, to prevent the ingress of dirt, it is strongly advised that the two modulesare not removed from the case (see Section 1.6).

1.3 Storage

If the relay is not required for immediate use, return it to its original wrapper andcarton and store in a clean, dry place. The silica gel unit supplied with relaysdelivered outside Britain should be heated at 60° – 70°C for one hour before beingreplaced.

1.4 Installation

Relays should be installed in a location free from excessive vibration. The relaycases can be supplied for rack mounting only. They are supplied in cases designedfor housing in standard 19 inch (483mm) racks.

1.5 Earthing

Ensure that the case earthing terminal above the rear terminal blocks is used toconnect the relay to the local earth (ground) bar.

1.6 Handling precautions against electrostatic discharge

A person's normal movements can easily generate electrostatic potentials of severalthousand volts. Discharge of these voltages into semiconductor devices whenhandling electronic circuits can cause serious damage, which often may not beimmediately apparent but the reliability of the circuit will have been reduced.

The electronic circuits of AREVA T&D products are completely safe from electrostatic discharge when housed in the case. Do not expose them to the risk of damage by withdrawing modules unnecessarily.

Each module incorporates the highest practicable protection for its semiconductordevices. However, if it becomes necessary to withdraw a module, the followingprecautions should be taken to preserve the high reliability and long life for whichthe equipment has been designed and manufactured.

MJTW 01 R 8124SERVICE MANUAL Chapter 3

Page 2 of 2

(1) Before removing a module, ensure that you are at the same electrostaticpotential as the equipment by touching the case.

(2) Handle the module by its handles, frame, or edges of printed circuit boards.Avoid touching the electronic components, printed circuit track, orconnectors.

(3) Do not pass the module to any person without first ensuring that you areboth at the same electrostatic potential. Shaking hands achievesequipotential.

(4) Place the module on an anti-static surface, or on a conductive surface whichis at the same potential as yourself.

(5) Store or transport the module in a conductive bag.

More information on safe working procedures for all electronic equipment can befound in BS5783 and IEC 147-0F.

If making measurements on the internal electronic circuitry of an equipment inservice, it is preferable to be earthed to the case with a conductive wrist strap. Thewrist strap should have a resistance to ground between 500k to 10M ohms. If a wriststrap is not available, regular contact with the case should be maintained to preventthe build up of static. Instrumentation which may be used for making measurementsshould be earthed to the case whenever possible.

AREVA T&D strongly recommends that detailed investigations on the electronic circuitry, or modification work, should be carried out in a Special Handling Area such as described in BS5783 or IEC 147-0F.


CHAPTER 4

HARDWARE DESCRIPTION


Page 1 of 5

Section 1. MECHANICAL DESCRIPTION

The MJTW 01 is constructed using the AREVA T&D MIDOS technology. With the exception of the voice frequency signalling circuits, all electrical connections are made to standard 28-way MIDOS terminal blocks fitted to the rear of the relay. The voice frequency signalling circuit connections are subject to public telecommunications licensing restrictions and use connections approved by the licensing body.

1.1 Relevant drawing numbers

Final assembly in 483mm rack mounted case BA0284Controller module BA0282Modem BA0226Outline BA0287External connection diagram F10 MJTW01 01

1.2 Relay mounting

The MJTW01 is housed in a 4U (178mm) high case suitable for semi-projecting483mm (19inch) rack mounting. The all-steel case is fitted with a steel front platewhich is affixed to the case by means of a hinge at the base. This allows the frontplate to hinge open downwards through 180° allowing access to the relay modules.To hold the front plate closed, a magnetic strip is provided which is reinforced bymeans of a lock and key to restrict unauthorised access. Test blocks etc. which maybe used in conjunction with the MJTW01 should be sited such that they are notobscured by the front plate when it is in the open position. With the front plateclosed, relay settings are not accessible, and indications are restricted to trip statusand evidence of communications failure and scheme fault conditions.

There are two modules referred to as the controller module and the modem. The twomodules are connected together electrically by means of 20-way insulationdisplacement connector (IDC) ribbon cable assembly. Either of the modules may beremoved from the case once the auxiliary dc supply has been removed by followingthe instructions given in Section 1.3.1 (controller module) and Section 1.3.2(modem).

The controller module is sited in the right of the relay case when viewed from thefront and is identified by a membrane keypad and liquid crystal display. The modemis to the left, and is identified by a black front approximately 230mm x 50mm withwhite screened printing.

1.3 Withdrawing modules

Before withdrawing modules from their case, the user should be familiar with theprecautions necessary when handling electronic equipment. See Chapter 3,Section 1.6.


Page 2 of 5

1.3.1 Controller module withdrawal

Swing out the two handles located at the top centre front, and bottom centre front ofthe controller module. Use the handles to partially extract the module from the case.Before the module can be completely withdrawn, the 20-way IDC ribbon cable mustbe detached from the module. This is done by using the two ejector levers fitted tothe connector attached to the aluminium screening plate of the controller module.

Note however that there are no user serviceable parts in the controller module, withthe exception of the fuse, see Chapter 10 on fault finding. Removal of the moduleshould be avoided unless absolutely necessary in order to minimise the risk ofdamage which may be caused by poor handling procedures.

1.3.2 Modem withdrawal

Unscrew the two captive screws located to the front right and front left of themodem module and partially withdraw the modem. To fully remove the modem it isnecessary to disconnect the 20-way IDC ribbon cable assembly by using the twoejector ears on the 20-way modem connector, and remove the two 15-way 'D'connectors which connect the modem to the DIN rail mounted terminal block byundoing the two screws which retain each 'D' connector. Finally, disconnect theprotective earth lead from the modem and fully withdraw the module.

When replacing the modules, ensure that all connectors are correctly re-fitted.Special attention should be paid to the protective earth connection on the modem.


Page 3 of 5

Section 2. RELAY HARDWARE DESCRIPTION

The MJTW01 comprises two modules housed together in a semi-projecting 483mmrack mounted case.

A block diagram of the MJTW01 is shown in Figure 3 page 3 of the salespublication (R-6124)which is included in Chapter 1. In addition to the sevenelements shown, there is also a power supply element to power the electroniccircuitry. The modem element is realised as one module and all the other elementsare contained in the controller module.

2.1 Controller module

The controller module is based around an industry standard 80C51 microcontrollerintegrated circuit. The software which controls the relay operation is stored in anEPROM program store and controls the scanning of inputs to generate digital bitpatterns which are transmitted in turn to the modem. Digital bit patterns are alsobeing constantly received from the modem and are used to determine the state therelay outputs should be in. A non-volatile data store is used to hold the relay settingswhich are entered through a user interface which features a liquid crystal display(lcd) and a membrane keypad.


Page 4 of 5

The controller module comprises five printed circuit boards which are listed with therelevant printed circuit board assembly numbers:

Microcontroller and power supply circuit board ZJ0149Display and keypad circuit board ZJ0084Opto-input circuit board ZJ0241Modem interface board ZJ0242Power supply filter board ZJ0811

The circuit schematic information for these printed circuit boards is contained inthree diagrams, the relevant numbers of which are as follows :

Controller module diagram 1 BA0282 01Opto-input circuit board schematic 1 ZJ0241 01Modem interface and relay output schematic 1 ZJ0242 01

These diagrams are available upon request.

The circuit schematic information for the microcontroller and power supply, thedisplay and keypad, and the power supply filter circuit boards is shown on thecontroller module circuit diagram. This diagram additionally shows the electricalinterconnection of all the printed circuit boards in the module.

Wherever possible, use has been made of ribbon cable assemblies to effectconnections between the printed circuit boards. Complementary metal oxide ofsilicon (CMOS) electronic components have been used to minimise the powerconsumption of the relay.

2.1.1 Controller module diagram (1 BA0282 01)

Sheet 1 of this diagram shows the power supply together with the non-volatilesettings store and the input buffers. Sheet 2 shows the microcontroller, the display,the keypad, the program store and the output buffers.

2.1.1.1 Microcontroller and periphery

Central to the MJTW01 relay is an industry standard 80C51 microcontrollerintegrated circuit (IC5). This is an 8-bit microcontroller which operates at 12MHz. Itis software controlled, with the program being stored in a 27C256 (IC17) which is a32kbyte programmable read only memory (EPROM). A serially accessed,electrically erasable programmable read only memory (EEPROM) provides a non-volatile data store (IC3) for setting information which prevents user defined settingsbeing lost in the event of a power failure to the equipment. There is a reset controller(IC2) which ensures orderly operation during power-up and power-down conditionsand, additionally, there is a watchdog circuit (D1, D2, etc.) which causes a resetcondition to be generated in the unlikely event of a software failure. All input andoutput circuitry is buffered by low-power CMOS electronic circuitry.


Page 5 of 5

2.1.1.2 Keypad

The membrane keypad (KBD1) has sixteen keys arranged as four banks of four.The operating software periodically activates each of the four banks in turn byasserting a strobe signal. Each of the four key-switches on the active bank thendrives a sense line indicating the state of the key to the microcontroller.

2.1.1.3 Display

An eight character, seven segment liquid crystal display (LCD1) is accommodatedtogether with its associated integrated circuit driver (IC1) on the display board fittedto the front of the controller module (ZJ0084). It is used in conjunction with thekeypad to allow the user to read and/or change the relay settings. In addition to thelcd there are also seven light emitting diodes (leds) to indicate trip and alarm status.Note that the led reference D8 is not fitted.

2.1.1.4 Power Supply

The +12V and +5V supply rails required by the controller module and modemcircuitry are derived from the auxiliary voltage supply by means of a switched modedc-dc flyback converter. Based around a 3524 regulating pulse width modulatorintegrated circuit (IC8), the power supply generates a fully isolated, regulated 12Vrail for the input and output circuit elements. This 12V rail is also regulated by aseries regulator integrated circuit (IC10) to give the 5V rail necessary to power theelectronic circuits. The input to the power supply and the output from the powersupply are both monitored and are used to signal power supply failure conditions tothe microcontroller circuitry.

There are two versions of power supply which together cover the whole range ofstandard substation battery voltages according to the table below.

Version Nominal Range(V)

Operative Range(V)

Low voltage 24/54 19.5 - 65.0High voltage 110/250 87.5 - 300.0

2.1.2 Opto-input circuit board (1 ZJ0241 01)

The opto-input circuit board contains three optically isolated input circuits used toinitiate tripping and testing and two miniature hinged armature relays used forindicating communications failure and equipment in test mode. The output relays areof pcb-mounted miniature attracted armature type and are powered from the 12Vrail. Each provides two pairs of normally open (form A) contacts.

The opto-input circuitry uses a strobing technique to reduce stress on the inputcircuitry components by ensuring that in the majority of the circuitry, current onlyflows when the state of the inputs is to be read. Under software control, themicrocontroller strobes the inputs by turning on the strobing opto-isolators(OPT2,4,6). This allows current to flow in the input opto-isolators (OPT1,3,5)according to whether the inputs have an auxiliary voltage applied to their terminals.The micro controller reads the inputs and then removes the strobe.


Page 6 of 5

There are two versions of opto-input circuitry which together cover a range ofstandard substation battery voltages according to the table below.

Version Nominal Range(V)

Operative Range(V)

Low voltage 24/54 19.5 - 65.0

High voltage 110/125 87.5 - 150.0

Fitted across the inputs of each of the opto-isolated input circuits are transientabsorption diodes (D7,8,9) and parallel pairs of 12W resistors (R1,2,3 andR23,24,25). The diodes protect against transient overvoltage conditions. Theresistors provide a power sink to provide the inputs with immunity to capacitivelycoupled power system frequency signals.

2.1.3 Modem interface and relay output circuit board (1 ZJ0242 01)

Printed circuit board ZJ0242 houses the interface to the modem and relay outputswhich signal trips received and scheme failure.

The modem interface consists simply of interconnection between the modem ribboncable assembly and the appropriate signals to the microcontroller.

The relay output elements use miniature hinged armature relays of pcb-mountedminiature attracted armature type which are powered from the 12V rail. There aretwo relay outputs, each providing two pairs of normally open (form A) contacts foreach of the trip outputs, giving a total of four form A contacts per trip output. Thereis also one normally closed contact to indicate a scheme fault. The scheme faultcontact is held normally open under healthy operating conditions of the MJTW 01; itwill close in the event of an equipment or scheme failure, or in the event of a loss ofauxiliary supply to the relay.

2.2 Modem module

The modem module is covered separately in the publication R-5927.


CHAPTER 5

MODEM

HANDLING OF ELECTRONIC EQUIPMENT

A persons normal movements can easily generate electrostatic potentials of several thousand volts. Discharge of these voltages into semiconductor devices when handling circuits can cause serious damage, which often may not be immediately apparent but the reliability of the circuit will have been reduced.

The electronic circuits of AREVA T&D products are immune to the relevant levels of electrostatic discharge when housed in their cases. Do not expose them to the risk of damage by withdrawing modules unnecessarily.

Each module incorporates the highest practicable protection for its semiconductor devices. However, if it becomes necessary to withdraw a module, the following precautions should be taken to preserve the high reliability and long life for which the equipment has been designed and manufactured.

1. Before removing a module, ensure that you are a same electrostatic potential as the equipment by touching the case.

2. Handle the module by its front-plate, frame, or edges of the printed circuit board. Avoid touching the electronic components, printed circuit track or connectors.

3. Do not pass the module to any person without first ensuring that you are both at the same electrostatic potential. Shaking hands achieves equipotential.

4. Place the module on an antistatic surface, or on a conducting surface which is at the same potential as yourself.

5. Store or transport the module in a conductive bag.

More information on safe working procedures for all electronic equipment can be found in BS5783 and IEC 60147-0F.

If you are making measurements on the internal electronic circuitry of an equipment in service, it is preferable that you are earthed to the case with a conductive wrist strap.

Wrist straps should have a resistance to ground between 500k 10M ohms. If a wrist strap is not available you should maintain regular contact with the case to prevent the build up of static. Instrumentation which may be used for making measurements should be earthed to the case whenever possible.


4

CONTENTS

SAFETY SECTION 6

1. GENERAL DESCRIPTION 101.1 Ancillary Circuits 101.2 Line signalling 10

2. WARNINGS 132.1 Connection of power supply 132.2 External control apparatus 132.3 Interconnections 132.4 Approval label 132.5 User instructions 13

3. TECHNICAL DATA 133.1 Signal levels 133.2 Timing 143.3 Logic levels 143.4 Carrier alarm relay 143.5 LED indicators 153.6 Front panel switches 153.7 Monitor test points 153.8 Physical 153.9 Environmental 153.10 Power supply requirements 153.11 High impedance mode (not BABT approved) 15

4. OPERATION 174.1 Line termination 174.2 Modulator 174.3 Timing 174.4 Test tone 174.5 Demodulator 174.6 Carrier alarm 184.7 Auxiliary circuits 18

5. OPTIONS 185.1 Model number options 185.2 User options 19

6. INSTALLATION 196.1 Mounting 196.2 Connections, four-wire circuits 196.3 Two-wire operation 206.4 Safety earth 21

7. SETTING UP 217.1 Selection of modem channel 217.2 Send level 227.3 High impedance option 22

5

8. COMMISSIONING 238.1 Send 238.2 Receive 238.3 Bias distortion 238.4 Monitor test points 23

9. MAINTENANCE 23

10. CIRCUIT DESCRIPTION 2410.1 Introduction 2410.2 Modulator 2410.3 Transmit filter 2510.4 Output attenuator and driver 2510.5 Receive buffer 2610.6 Receive filter and delay equaliser 2610.7 Discriminator 2610.8 Carrier detected 2710.9 Carrier alarm 2710.10 Auxiliary receive and send circuits 2710.11 External transmit clock 2810.12 Analogue loopback 28

CIRCUIT DIAGRAM 29

6

SAFETY SECTION

This Safety Section should be read before commencing any work on the equipment.

Health and safety

The information in the Safety Section of the product documentation is intended toensure that products are properly installed and handled in order to maintain them ina safe condition. It is assumed that everyone who will be associated with theequipment will be familiar with the contents of the Safety Section.

Explanation of symbols and labels

The meaning of symbols and labels which may be used on the equipment or in theproduct documentation, is given below.

Caution: refer to product documentation Caution: risk of electric shock

Protective/safety *earth terminal

Functional *earth terminal.Note: this symbol may also be used for a protective/safety earth terminal if that terminal is part of aterminal block or sub-assembly eg. power supply.

*Note: The term earth used throughout the product documentation is the directequivalent of the North American term ground.

Installing, Commissioning and ServicingEquipment connections

Personnel undertaking installation, commissioning or servicing work on thisequipment should be aware of the correct working procedures to ensure safety.The product documentation should be consulted before installing, commissioning orservicing the equipment.

Terminals exposed during installation, commissioning and maintenance may presenta hazardous voltage unless the equipment is electrically isolated.

If there is unlocked access to the rear of the equipment, care should be taken by allpersonnel to avoid electric shock or energy hazards.

Voltage and current connections should be made using insulated crimp terminationsto ensure that terminal block insulation requirements are maintained for safety. Toensure that wires are correctly terminated, the correct crimp terminal and tool for thewire size should be used.

7

Before energising the equipment it must be earthed using the protective earthterminal, or the appropriate termination of the supply plug in the case of plugconnected equipment. Omitting or disconnecting the equipment earth may cause asafety hazard.

The recommended minimum earth wire size is 2.5 mm2, unless otherwise stated inthe technical data section of the product documentation.

Before energising the equipment, the following should be checked:

Voltage rating and polarity;

CT circuit rating and integrity of connections;

Protective fuse rating;

Integrity of earth connection (where applicable)

Equipment operating conditions

The equipment should be operated within the specified electrical and environmentallimits.

Current transformer circuits

Do not open the secondary circuit of a live CT since the high voltage producedmay be lethal to personnel and could damage insulation.

External resistors

Where external resistors are fitted to relays, these may present a risk of electric shockor burns, if touched.

Battery replacement

Where internal batteries are fitted they should be replaced with the recommendedtype and be installed with the correct polarity, to avoid possible damage to theequipment.

Insulation and dielectric strength testing

Insulation testing may leave capacitors charged up to a hazardous voltage. At theend of each part of the test, the voltage should be gradually reduced to zero, todischarge capacitors, before the test leads are disconnected.

Insertion of modules and pcb cards

These must not be inserted into or withdrawn from equipment whilst it is energised,since this may result in damage.

Fibre optic communication

Where fibre optic communication devices are fitted, these should not be vieweddirectly. Optical power meters should be used to determine the operation or signallevel of the device.

8

Older ProductsElectrical adjustments

Equipments which require direct physical adjustments to their operating mechanism tochange current or voltage settings, should have the electrical power removed beforemaking the change, to avoid any risk of electric shock.

Mechanical adjustments

The electrical power to the relay contacts should be removed before checking anymechanical settings, to avoid any risk of electric shock.

Draw out case relays

Removal of the cover on equipment incorporating electromechanical operatingelements, may expose hazardous live parts such as relay contacts.

Insertion and withdrawal of extender cards

When using an extender card, this should not be inserted or withdrawn from theequipment whilst it is energised. This is to avoid possible shock or damage hazards.Hazardous live voltages may be accessible on the extender card.

Insertion and withdrawal of heavy current test plugs

When using a heavy current test plug, CT shorting links must be in place beforeinsertion or removal, to avoid potentially lethal voltages.

Decommissioning and Disposal

Decommissioning: The auxiliary supply circuit in the relay may include capacitorsacross the supply or to earth. To avoid electric shock or energyhazards, after completely isolating the supplies to the relay(both poles of any dc supply), the capacitors should be safelydischarged via the external terminals prior to decommissioning.

Disposal: It is recommended that incineration and disposal to watercourses is avoided. The product should be disposed of in a safemanner. Any products containing batteries should have themremoved before disposal, taking precautions to avoid shortcircuits. Particular regulations within the country of operation,may apply to the disposal of lithium batteries.

9

Technical SpecificationsProtective fuse rating

The recommended maximum rating of the external protective fuse for this equipmentis 6A, GEC Red Spot type or equivalent, unless otherwise stated in the technical datasection of the product documentation.

Insulation class: IEC 1010-1: 1990/A2: 1995 This equipment requires aClass I protective (safety) earthEN 61010-1: 1993/A2: 1995 connection to ensure userClass I safety.

Installation IEC 1010-1: 1990/A2: 1995 Distribution level, fixedCategory Category III installation. Equipment in(Overvoltage): EN 61010-1: 1993/A2: 1995 this category is qualification

Category III tested at 5kV peak, 1.2/50µs,500Ω, 0.5J, between all supplycircuits and earth and alsobetween independent circuits.

Environment: IEC 1010-1: 1990/A2: 1995 Compliance is demonstrated byPollution degree 2 reference to generic safetyEN 61010-1: 1993/A2: 1995 standards.Pollution degree 2

Product safety: 73/23/EEC Compliance with the EuropeanCommission Low VoltageDirective.

EN 61010-1: 1993/A2: 1995 Compliance is demonstratedEN 60950: 1992/A3: 1995 by reference to generic safety

standards.

10

Section 1. GENERAL DESCRIPTION

Modem BA0226 uses frequency shift keying (FSK) and is for use on either privaterented or privately owned circuits. It may be set to operate at one of a number ofdifferent baud rates and frequency channels as shown in Table 1, and features multi-channel operation at 200, 300, 600 or 1200 baud and fast FSK (FFSK) at 1500baud. It is thus ideal for applications where limited bandwidth speech, other dataequipment or several modems require to share the same bearer circuit.

Operating frequencies are selected by means of a plug-in crystal and switchselectable counters. Filter characteristics are realised by the use of switched capacitorfilters programmed by a plug-in resistor header to achieve CCITT V.23 and R38Achannels or the implementation of other non-standard channels.

The apparatus is primarily intended for four-wire operation with 600 ohm balancedtermination, but is internally linkable to two-wire operation. Line isolation is achievedusing barrier transformers. The fully enclosed unit is intended for mounting in a 6Uhigh Euro sub-rack, but may alternatively be used in a stand-alone mode.

1.1 Ancillary Circuits

In addition to the main transmit and receive functions, the following ancillary circuitsare provided as shown in the block diagram Figure 1.

(i) Combining and branching amplifier for the tee connection of an externalAPPROVED 600 ohm presented equipment (such as another alternative channelmodem for example).

(ii) A high impedance line option for use with external isolation transformers on aprivate network not subject to BABT approval.

(iii) Internal loopback and a test tone generator which can transmit a continuous0101 pattern for level setting and bias adjustment.

(iv) Adjustable bias for minium receiver distortion.

(v) Carrier fail detector plus upper and lower carrier level alarm.

(vi) Output boost control.

(vii) A transmit data clock pulse at the appropriate data rate, which may be eitherasynchronous for CCITT recommended channels or synchronous, asappropriate, for ‘special’ channels.

1.2 Line signalling

The apparatus is not generally suitable for use on circuits with BritishTelecommunications signalling at 2280Hz. On such circuits, only the followingchannels may be used.

600 baud, channel 1

300 baud, channels 2, 3 and 6.

The apparatus is suitable for point-to-point and multipoint circuits.

The apparatus does not require signalling and does not use frequencies below300Hz.

The apparatus does not require any dc interaction with British Telecommunicationsprivate circuits.

11

Channel Baud rate Centre Mode Usedfrequency bandwidth

CCITT402 200/300 1080Hz ASYNC ±240Hz

CCITT403 200/300 1560Hz ASYNC ±240Hz

CCITT404 200/300 2040Hz ASYNC ±240Hz

CCITT405 200/300 2520Hz ASYNC ±240Hz

CCITT406 200/300 3000Hz ASYNC ±240Hz

CCITT V23 600 1500Hz ASYNC ±400Hz

SPECIAL 600 2500Hz ASYNC ±400Hz

CCITT V23 1200 1700Hz ASYNC ±800Hz

FFSK 1500 1875Hz SYNC ±800Hz

*

* Other special channels available to order (non-approved)

Table 1 Available modem frequencies

12

Rece

ive

filte

r30

dB

Anal

ogue

loop

back

Equa

liser

0 ±1

5dB

0 –

00Re

ceiv

ed V

F

Auxi

liary

inpu

t

Inpu

t lev

elad

justm

ent

High

leve

lde

tecto

r

Carri

erde

tecto

r

1

Phas

e lo

cklo

op d

iscrim

inat

or&

Auxi

liary

outp

ut

Carri

er a

larm

Data

car

rier

dete

cted

Rece

ived

data

Send

VF

Clea

r to

send

Cons

tant

curre

nt so

urce

Out

put l

evel

adju

stmen

t

Send

filte

r

0 –

15dB

Tone

gene

rato

r

Test

data

Send

dat

a

Boos

t

Requ

est t

o se

nd

Dela

y

Clea

r to

send

0 ±1

5dB

Figu

re 1

Blo

ck d

iagr

am

13

Section 2. WARNINGS

2.1 Connection of power supply

This apparatus is intended for use when supplied with power from a 12V dc sourcewith characteristics as specified in Section 3.10 and which complies with the relevantlegal safety requirements when properly assembled, installed and maintained.The host apparatus must be able to supply adequate power for the modem plus anyother auxiliary apparatus drawing power from it. Other usage will INVALIDATEany approval given to this apparatus if, as a result, it ceases to comply withBS 6301:1982.

2.2 External control apparatus

The approval of this modem for connection to British Telecommunications PrivateSpeechband circuits is INVALIDATED if the apparatus is subject to any modificationin any material way not authorised by BABT or if it is used with, or connected toexternal control software or external control apparatus which causes the operation ofthe modem or associated call set-up equipment to contravene the requirements of thestandard set out in BABT/SITS/82/01/C.

All apparatus connected to this modem and thereby connected directly or indirectlyto British Telecommunications Private Speechband circuits must be approvedapparatus as defined in Section 16 of the British Telecommunications Act 1981.

2.3 Interconnections

The interconnection either directly, or by way of other apparatus, of this modem withports marked in accordance with BS 6301: 1982 Clause 4.3.1a may producehazardous conditions on the BT network and advice should be obtained from acompetent engineer before such connection is made.

2.4 Approval label

Users are reminded that it is the modem that is approved and not any hostapparatus. Furthermore, the BABT Assessment Symbol and Approval Label must beapplied to the modem and NOT to the host.

2.5 User instructions

These modem user instructions MUST be supplied with any host apparatus.Failure to do so will INVALIDATE the Modem Approval.

Section 3. TECHNICAL DATA

3.1 Signal levels

3.1.1 Modem send level

Adjustable in 1dB steps from –13.5 to –28.5dBm ±0.5dB. The output may also beboosted under external logic control by 3dB; see WARNING below.

3.1.2 Modem receive level

The modem may be set to receive at a level in the range –5 to –30dBm. Correctoperation is maintained within a margin of –10dB to + 13dB with respect to settingup level.

14

A carrier fail detector operates at a level of –12dB ± 2dB with respect to setting uplevel, and a carrier alarm output is given at levels of –6dB ±2dB and +12dB ±2dBwith respect to setting up level.

3.1.3 Auxiliary circuits

Auxiliary circuits are provided to perform a combining and branching functionbetween the AUX IN and main SEND circuits, and between the main RECEIVE andAUX OUT circuits. Each circuit may be adjusted in gain over the range +15dB to–15dB in 1dB steps.

WARNING

For connection to public network privately rented circuits, the maximum level to lineof the modem and auxiliary circuits, including any boost facility, must not exceed–13dBm for a single channel or 50 microwatts total power averaged over 1 minutefor more than one channel.

The boost facility is intended for use with host apparatus which is accessible only toauthorised personnel. The apparatus must be installed in a locked room or cubiclesuch that user access is prevented. Failure to prevent such user access will invalidateany approval given to this apparatus.

3.2 Timing

3.2.1 Request to send/clear to send.

The modem output is turned on by the request to send signal. A clear to send signalis output after 32ms ±20%.

3.2.2 Carrier detected

Output time 12ms ±20% after receipt of VF signal.

3.2.3 Data propagation delay

200/1500 baud 3ms

600 baud 6.5ms

200/300 baud 13ms

These times do not include propagation times due to the transmission medium.

3.3 Logic levels

3.3.1 Send data, request to send and boost are input signals at 5V TTL logic levels.

3.3.2 Receive data, carrier detected and clear to send are free collector transistor outputsfor connection at up to 12V dc.

3.3.3. External transmit clock output.

5V TTL logic output, square wave at data rate. Logic ‘0’ to logic ‘1’ transition atcentre of bit. New data set up on logic ‘1’ to logic ‘0’ clock edge.

3.4 Carrier alarm relay

Single make contact.

Maximum switched voltage 50V.

Maximum switched current 1A.

Maximum switched power 30W.

15

3.5 LED indicators

TEST Illuminated in test mode if unit transmitting continuous frequency low orcontinuous 0101 test pattern.

RTS Request to send. ON if VF Send requested.

SD Send data. ON if data logic low (Space).

RD Receive data. RED = Space (logic low). GREEN = Mark (logic high).ORANGE = Switching data

DCD Data carrier detected. ON if input signal present at sufficient level forcorrect operation.

CA Carrier alarm. ON if input level is either too high or too low.

3.6 Front panel switches

3.6.1 NORMAL Normal operating mode

TEST MK. Transmits continuous low tone

TEST BIAS Transmits continuous 0101 pattern.

3.6.2 Loopback

Connects transmitter analogue output to receive analogue input to allow local testing.

3.6.3 Termination

Modem and Auxiliary Send outputs may be switched either ON or OFFindependently. Either may be terminated by line or by internal load for testmeasurements.

3.7 Monitor test points

See Chapter 8 – Commissioning.

3.8 Physical

The unit is designed to fit the guide rails of a standard 6U high Euro sub-rack.Front panel dimensions 50.8mm wide x 262 mm high. Overall unit depth includingconnectors 280mm.

3.9 Environmental

Working temperature: –10°C to +55°C

Humidity: 5% to 95% RH at 40°C non-condensing

3.10 Power supply requirements

Voltage: 12V dc ±0.6V dc

Current: 90mA max.

Ripple: To be less than 5mV peak

Noise: High frequency switching spikes not greater than50mV peak to peak and 1µs wide.

3.11 High impedance mode (not BABT approved)

When working with external line termination transformers supplied by manufacturer,input and output impedances >10kΩ.

16

Figure 2 Panel layout

NORMALTEST MKTEST BIAS

TEST

RTS

SD

RO

DCD

CA

BIAS

SET RXLEVEL

RDSDRXF5V0V0V

AUXMODEM

TERMINATION INT OFF OFF INT

SEND

THRO ON ON THRO

TOAUX

FROMAUX

SETLEVEL

SEND

REC

TO AUX

FROM AUX0V

MODEMBA0226

NORMAL

LOOPBACK

LINE MONITOR

11

SendTELEPHONE

LINEReceive

AUXLINE

DTE

17

Section 4. OPERATION

4.1 Line termination

Isolation of the transmission medium is provided by barrier transformers associatedwith each of the send, receive and auxiliary circuit lines. Signal voltage limitingdiodes are also provided on each line circuit.

4.2 Modulator

The frequency source is a crystal-controlled oscillator driving a logic divider with twodifferent division ratios. The appropriate ratio, and thus the output frequency, isdetermined by the state of the serial binary data input. The square wave, which isswitched on and off by a logic control, passes to the output via a bandpass filter tolimit the sidebands and harmonics, both in the alternative channels and also to meetthe British Approvals Board for Telecommunications level requirements above3.4kHz. Following the filter is a line driver giving high output impedance, which maybe coupled via special external line transformers to provide high impedancetermination on certain private circuits, but which is terminated in 600 ohmimpedance via the internal isolation transformers for connection to public networkprivate circuits.

4.3 Timing

The request to send input signal causes the output tones to be switched on. However,a delay is introduced to allow the filters and receiver detection circuits to settle beforethe clear to send reply signal is given.

4.4 Test tone

A test switch at the front of the unit allows either a steady MARK tone (frequencylow), or a square wave data pattern at maximum baud rate, to be transmittedcontinuously thus allowing receiver levels and bias distortion to be set.

4.5 Demodulator

The VF input tones are conditioned by a buffer amplifier before passing to a four-stage active bandpass filter using switched capacitor techniques. The buffer amplifierincorporates a variable gain control (adjustable from the front of the unit) togetherwith a fixed attenuator, which may be switched in and out of circuit by means of apushbutton. When the pushbutton is depressed, the attenuator is switched into circuitand the level setting potentiometer may then be adjusted until Data Carrier Detectedgoes false as indicated by the extinguishing of an led. If the gain is then increaseduntil the led re-illuminates and the pushbutton is released, the gain will be increasedby a further 10dB (approximately) to give the optimum working level into the filterand discriminator circuitry.

The VF signal from the filter then passes via a group delay equaliser to a phaselocked loop (PLL) discriminator. The PLL output is conditioned by a low pass filter anddata slicer to restore logic level signals at the serial received data terminal.A second analogue to logic level translator forms part of the carrier detector circuit.It passes VF tones from the filter to a diode-pump circuit, which after a few cycles ofcarrier switches the detector output. A further delay is introduced, however, both toprotect against the circuit being switched by transient noise spikes on the incomingline and also to allow the PLL sufficient settling time before Receiver Ready is madetrue.

18

4.6 Carrier alarm

In addition to the Carrier Fail detector, two other level detectors are provided to givewarning if the received input level becomes either too high or too low, relative to theset-up working level. The high level warning operates approximately 12dB above thenormal receive level to indicate that saturation of the input circuits may occur.The low level warning operates approximately 6dB below normal receive level toindicate that receive conditions are deteriorating.

4.7 Auxiliary circuits

The incoming main Receive signal also passes to a separate amplifier havingadjustable gain, where the signal may be either boosted or attenuated before beingfed to a high output impedance auxiliary line driver circuit. As with the main sendoutput, this may be coupled either via external transformers or via the internal 600ohm matched line isolation circuit.

An adjustable gain Receive amplifier is also provided for signals received from anauxiliary input circuit, so that incoming signals may be balanced in level, beforebeing combined with the output from the modem.

Section 5. OPTIONS

5.1 Model number options

The model number is of the form BA0226 XYZ where XYZ is a three digit code whichdefines the send and receive sections of the modem in accordance with the channeloption number as follows:

Channel option Send andreceive Send and receive

same channel different channelsNumber Description X Y Z

1 200/300 baud channel 2 0 0 1

X = 1

2 200/300 baud channel 3 0 0 2

Y = Send channeloption number

3 200/300 baud channel 4 0 0 3

4 200/300 baud channel 5 0 0 4 Z = Receive channeloption number

5 200/300 baud channel 6 0 0 5

6 600 baud 1500Hz 0 0 6

7 600 baud 2500Hz 0 0 7

8 Not yet available 0 0 8

9 Not yet available 0 0 9

10 1200 baud 1700Hz 0 1 0

11 1500 baud 1875Hz 0 1 1

19

5.2 User options

5.2.1 Auxiliary amplifier gains

LK 4a Auxiliary Send gain range 0 to +15dB

LK 4b Auxiliary Send gain range 0 to –15dB

LK 25a Auxiliary Receive gain range 0 to +15dB

LK 25b Auxiliary Receive gain range 0 to –15dB

5.2.2 Carrier alarm relay

LK 42a Alarm condition, contact normally open

LK 42b Alarm condition, contact normally closed

For other link options see Sections 7 and 8.

Section 6. INSTALLATION

6.1 Mounting

The modem is mounted in the guide rails of a 6U high Euro sub-rack DIN 41494.A depth of 280mm is required. The unit should be secured in place by the front panelfixing screws.

Telephone line connections are via a 15-way ‘D’ type SOCKET at the rear of the unit,normally supplied with 2.5 metres (nominal) cable.

Auxiliary line and high impedance termination connections are via a 15-way ‘D’ typeplug at the rear of the unit.

Data line and power connections are via a 20-way ribbon cable connector at therear of unit.

6.2 Connections, four-wire circuits

6.2.1 Telephone line ‘D’ type. (PL1)

SEND

Pin 7 Cable colour Green

Pin 14 Cable colour Yellow or Brown

RECEIVE

Pin 2 Cable colour Blue

Pin 10 Cable colour Red or Orange

6.2.2 Auxiliary circuits ‘D’ type. (SK1)

Pin No

To AUX RECEIVE 600 ohm: Hi 1

Lo 9

From AUX SEND 600 ohm: Hi 15

Lo 8

SEND high impedance: Hi 3

Lo 11

20

Pin No

RECEIVE high impedance: Hi 4

Lo 12

To AUX RECEIVE high impedance: Hi 5

Lo 11

From AUX SEND high impedance: Hi 6

Lo 13

6.2.3 Ribbon cable connections

Pin No.

1 Monitor alarm TMA (Not used)

2 Clear to send CTS

3 Request to send RTS

4 0V

5 Ext. Tx Clock

6 Ext. Rx Clock (Not used)

7 0V

8 Spare

9 Spare

10 Send Data SD

11 Boost

12 Data carrier detected (DCD)

13 Receive data RD

14 0V

15 +5V (Not used)

16 –12V (Not used)

17 +12V

18 +12V

19 Carrier alarm

20 Carrier alarm

6.3 Two-wire operation

6.3.1 Telephone line

Connect as SEND line Pin 7 Colour Green

Pin 14 Colour Yellow or Brown

6.3.2 Connect auxiliary connector as follows:

Pin 4 to Pin 3

NO AUXILIARY OR HIGH IMPEDANCE CONNECTIONS ARE PERMITTED.

Ribbon cable connections are as detailed in 6.2.3 above.

21

6.4 Safety earth

A protection earth to the metal case is required as part of the user protection circuit.This is normally achieved automatically via the front fixing screws when mounted inan earthed sub-rack. If an earthed sub-rack is not available, then a safety earth leadshould be connected via the Faston connector at the rear of the unit.

Section 7. SETTING UP

7.1 Selection of modem channel

Data channels are provided with baud rate, centre frequency, upper and lowercharacteristic tones as specified in Table 2 below.

Channel Baud Centre Lower Upperoption rate frequency tone tone

fo fl fh

1 200/300 1080Hz 960Hz 1200Hz

2 200/300 1560Hz 1440Hz 1680Hz

3 200/300 2040Hz 1920Hz 2160Hz

4 200/300 2520Hz 2400Hz 2640Hz

5 200/300 3000Hz 2880Hz 3120Hz

6 600 1500Hz 1300Hz 1700Hz

7 600 2500Hz 2300Hz 2700Hz

8* 600 – – –

9* 600 – – –

10 1200 1700Hz 1300Hz 2100Hz

11 1500 1875Hz 1500Hz 2250Hz

*Not yet available

Table 2 Channel frequencies

The upper tone represents data logic’ 0' (SPACE) state and the lower tone representsdata logic’ 1' (MARK) state.

To set up the modem for a particular channel operation, select the appropriate optionitems as specified in Section 5.1. Remove top cover of modem by removing fourscrews on top of cover and two screws at side of cover. Plug selected headers andcrystal into modem and set links and switches as indicated in Table 3.

Note: Units are normally supplied factory pre-set to order.

22

Channel Baud Crystal Links Switch S4option rate freq.MHz 1 2 3 4 5 6 7 8

1 300 4.9152 14A 28A 38 6B 11A 13B A B B B B A A A

2 300 5.1610 13A 28A 38 6B 11A 14B A B B B A B A A

3 300 4.4237 12A 28A 38 6B 11A 14B A B B B B B A A

4 300 6.7584 12A 28A 38 6B 11A 14B A B B B A A B A

5 300 4.7923 17A 28A 38 6B 11A 14B A B B B B A B A

6 600 5.6576 14A 28A 37 6B 11A 13B A A A B B A A A

7 600 3.9744 12A 28A 37 6B 11A 14B A A B B A B A A

8 600 4.9152 16A 28B 38 6B 9A 14B A B B A A A A A

9 600 3.6864 13A 28B38 11B 9A 12B A B B A B A A A

10 1200 6.9888 15A 28A 36 6B 11A 14B B B A B A A A A

11 1500 4.6080 14A 28B 38 6B 11A 12B A B B B A A A A

Table 3 VF tone selection

For BABT approved usage check following links:

Four-wire operation LK27, LK30, LK35, LK40 OPEN

LK23, LK24, LK26, LK41 FITTED

Two-wire operation LK26, LK27, LK40, LK41 OPEN

LK23, LK30, LK35, FITTED

Auxiliary circuits LK4 and LK 25 to position B (0dB gain)

7.2 Send level

The transmit output level to line should be –13.5 +0.4dBm when connected to acorrectly terminated 600 ohm load. This level must be checked during commissioningand may be adjusted slightly by pre-set potentiometer RV6, if necessary.This potentiometer is factory pre-set and should not be adjusted in normal service.

The output level may be attenuated by up to 15dB using fixed switched attenuatorslocated at the front of the unit as shown in Figure 2.

Attenuators are switched in steps of 1dB, 2dB, 4dB and 8dB and are additive.

7.3 High impedance option

For high impedance operation (via external barrier transformers) the following linkarrangement should be used:

LK27 LK30 LK35 LK40 FITTED

LK23 LK24 LK26 LK41 OPEN

23

Section 8. COMMISSIONING

To facilitate setting-up, set switch S1, located at the front of the unit, to the TEST MKposition. This will cause the unit to continuously transmit a square wave data patternat maximum baud rate. Set AUX to OFF during tests.

8.1 Send

Check for correct send level as specified in Section 7.2. Check that the averagefrequency is the channel centre frequency fo as per Table 2.

Note: If more than one VF tone is to be present on the line, the total mean powermust not exceed 50 microwatts, ie. if two channels are present, the sendlevel must be -16 dBm etc.

8.2 Receive

With the modem receiving tones transmitted as described in Section 8.1, depresspushbutton PB1 on the front of the unit and adjust SET RECEIVE LEVEL potentiometerRV2 until light emitting diode RECEIVE (D2) is just extinguished. Turn RV2 clockwiseuntil D2 re-illuminates and release PB1. The modem receive level is now correctly set.

8.3 Bias distortion

Observe the waveform at test point RD, using an oscilloscope, and adjust BIASpotentiometer RV1 to give a square wave output with equal mark-space ratio. If anoscilloscope is not available, an approximate setting may be obtained using anAvometer on 10V dc range and adjusting RV1 to give a reading of 2.4V.

8.4 Monitor test points

The main Receive VF signals and Send VF signals from an auxiliary equipment maybe monitored at test points on the front panel. These test points are on the customerside of the internal barrier transformer and give a reading approximately 2dB lessthan the true signal level on the line.

Test points for main Send VF signals and VF signals to the receiver of an auxiliaryequipment are also provided. These test levels are approximately 2dB greater thanthe true level to line.

Section 9. MAINTENANCE

The modem should not need regular routine maintenance.

Where a user adopts a policy of routine checking to assess line quality etc. thencommissioning tests 8.1 to 8.3 may be used.

When a fault does occur, the unit should be returned to the manufacturer for repairand testing. Because of the use of CMOS technology and pre-aligned filters, servicein the field is not recommended.

24

Section 10. CIRCUIT DESCRIPTION

10.1 Introduction

The description should be read in conjunction with circuit diagram L1BA0226 01,and covers the system functions of:

i) modulation and demodulation to send and receive data via some communicationmedium.

ii) timing logic for turning the unit on and level checking circuits to test theadequacy of received signals.

iii) combining and branching amplifiers.

The main logic functions use high speed CMOS 74HCxx series integrated circuitsoperating from 5V dc. Analogue functions operate from effectively ±6V suppliesderived from the single 12V supply input.

10.2 Modulator

The tone frequencies produced by the modulator are derived from the crystaloscillator circuit consisting of crystal X1, IC17 and associated components.The crystal frequency is selected to be divisible to give the required tones for eachchannel. The division is performed in two stages: a variable division dependingupon the data input and a fixed division performed by IC23, which is selectableusing links 12 to18.

The variable divider IC16, IC25 is loaded with a pre-set value selected by switchesS4/1 to S4/7, and counts from this value minus 1 to either 128 or 136.

The division required may be expressed as N + 1 or N – 1 where

channel arithmetic centre frequency1/2 (upper minus lower characteristic frequency)

N + 1 136 – (L – 1)= where L = preset load value

N – 1 128 – (L – 1)from which L = 133 – 4N

Thus for 1200 baud channel, say

1700 17N = =

1/2 (2100–1300) 4

from which L = 116

This is set by switches S4/1 to S4/7 in pattern BBABAAA.

The fixed division is 2k where k lies between 4 and 9 inclusive.

For 1200 baud k = 8, hence link 15A is selected.

With input data high (logic ‘1’), the count will progress to 136 before gate IC24/3goes low, causing IC15/9 to be set low on the negative- going edge of the clock.The counters are, therefore, primed to load the preset value, which occurs on the nextpositive clock edge. Half a clock pulse later, IC15/9 is re-set to logic ‘1’ and thecounters re-start the sequence. The lower tone is thus produced.

N =

25

When the input data is logic ‘0’, IC24/6 is permanently enabled and the count willonly go to 128 before the re-load sequence occurs. Thus the count is shorter and thehigher tone is produced.

The modulator is turned ON by enabling IC23/11 with either the input signal‘Request to Send’ or an output from switch SW1 when in either of the test positions.‘Request to Send’ also opens gates IC4/4 and IC3/6 to turn ON transistor TR8 andgive a ‘Clear to Send’ output after a delay of approximately 30ms, timed bymonostable IC26/6.

10.3 Transmit filter

The four stage filter is based on an R5622 (IC8) resistor programmable universalactive filter. Each of the four sections comprises a two integrator state variablesecond order switched capacitor filter, whose time constant is controlled by thesample rate applied to the filters. All of the standard filter transfer functioncharacteristics can be controlled by feeding back the output signal to one or more ofthe three inputs. For example, the gain from Vout to LP controls the filter clock tocentre ratio and the gain from Vout to BP– can be used to control the Q of the secondorder section.

The filter uses a constant clock frequency of 115.2kHz and is configured by means ofresistors on a plug-in header. For 200/300 baud working, the filter is configured asfour stagger-tuned bandpass sections, whilst for 600 and 1200 baud working, thefirst three sections are bandpass and the fourth is an elliptical low-pass (notch)section. This provides sharper cut-off at the upper end of the passband for 600 baudchannel 1 and 1200 baud working. For 600 baud channel 2, the fourth section isconfigured as an elliptical high pass filter, giving sharper cut-off at the lower end ofthe pass band.

The output resistor on pins 2 and 27 of the header, together with C4, providescompensating roll-off and reduces the level of high frequency switching clockbreakthrough. All channel filters are designed to have the same nominal insertionloss, this being in the range 13 to14dB.

10.4 Output attenuator and driver

The output from the filter passes via buffer amplifier IC7/1 whose gain may beincreased 3dB by turning ON transistor TR1 under the control of the logic input‘Boost ‘. This drives an attenuator network containing four T section pads giving1dB, 2dB, 4dB and 8dB attentuation, respectively.

Amplifier IC27/8 is a summing amplifier which combines the data and signals fromthe auxiliary circuit, before being driven to line by the high output impedance driverIC27/14. Switches SW3/b and SW3/c allow the data and auxiliary signalsrespectively to be switched ON and OFF independently for setting up purposes.The auxiliary circuit input has 0dB gain, but may be set to +15dB gain under specialcircumstances by changing LK4 to the A position. Data output may be changedapproximately ±3dB by potentiometer R94 but is normally preset to give a data levelto line of –13.5dBm. Switch SW3/a allows the circuit to be driven into an internalload for test purposes, or via the output line barrier transformer T1 with its frequencycompensating components C47, C88.

26

10.5 Receive buffer

After passing through a line barrier transformer T2, with its associated protectiondiodes D19 D24, and frequency compensation capacitors C43 C69, the received VFsignal may be attenuated by potentiometer R2 before passing to amplifier IC18/7.This has a nominal gain of 30dB, but high pass filtering by C44/R2 and C30/R62reduces the effect of 50Hz pick-up by approximately 12dB.

By closing the ‘Set Receive Level’ pushbutton, the overall gain is reduced by 10dB.This allows easy setting up by reducing the input sensitivity using R2 until the DataCarrier Detected led is extinguished, and then increasing sensitivity until the led re-illuminates. When the pushbutton is released, the correct working margin of 10dBabove turn-on level is established.

10.6 Receive filter and delay equaliser

The actual Receive filter uses an identical circuit configuration to the Transmit filter asdescribed in Section 10.3. Additional receiver gain is provided by amplifier IC19/7which has 12 dB nominal gain. Capacitors C24 and C31 provide high frequencyroll-off to reduce noise caused by breakthrough of the high frequency filter switchingclock. The output from IC19/7 drives the carrier detector circuitry and a delayequaliser formed around IC21. This is a dual two integrator state variable secondorder switched capacitor filter configured to work as a stagger-tuned all pass filter.It provides group delay equalisation whilst maintaining unity gain at all frequencies.Resistors, which vary with selected channel, are mounted on a separate plug-inheader together with discriminator components.

10.7 Discriminator

The discriminator is formed around an XR2211 phase-locked loop detector, IC13,whose free-running frequency is determined by C23 and R1, plus a resistor Rx.Since this frequency varies with each channel, resistor Rx is mounted on the plug-inheader (pins 2 and 23) particular to each channel. The resistor on pins 1 and 24determines the loop tracking bandwidth and the capacitor on pins 4 and 5 sets theloop damping. When in lock, the output from the loop phase detector IC13/11 ispassed via a post detect filter R74/C26 and RN2/CF to an amplifier IC14/1 andSallen-key low pass filter formed around IC14/7. Capacitor CF is mounted on pins20 and 21 of the header and is selected according to baud rate, but the fixed low-pass filter is tuned to 600Hz to provide attenuation of carrier frequencies, whilstpassing data frequencies. The filter output (sometimes known as the eye-pattern) isconnected to an FSK comparator inside the PLL (IC13), where it is compared to areference voltage and gives out data in the form of logic ‘0’s and ‘1’s. Resistor R59provides positive feedback across the comparator to facilitate rapid transitionbetween output logic states.

When no carrier frequency is present, the phase-locked loop will hunt and randomoutput data is produced. To prevent this being passed on, the data output is gatedwith ‘Data Carrier Detected’ in IC4/1 such that it is held in the logic ‘1’ idle stateuntil genuine carrier presence is detected, thus allowing only good data on signalRD. A bi-coloured led(D4 ), is biased to mid- supply voltage, such that it glows eitherred or green depending upon whether IC11/4 is low or high, respectively.

27

10.8 Carrier detected

The VF output from the receive filter also drives amplifier IC19/1 – providingapproximately 8 dB gain ≠ and then an analogue to logic converter IC19/8, whichoperates down to levels corresponding to an input of approximately –42dBm.There is local hysteresis to define the switching threshhold of IC19/8 and also anoverall hysteresis via transistor TR6, which effectively increases the sensitivity byabout 3dB once carrier is detected.

The output of IC19/8 drives a diode-transistor pump circuit D11, TR5, C9, C10,which requires a few cycles of carrier to pump down the voltage on C9 to a pointwhere level comparator IC19/14 switches. Capacitor C9 is being constantly re-charged by a resistor on pins 3 and 22 of plug-in header, whose value varies withchannel frequency. When carrier is lost, it requires a time of typically 2 to 4ms tore-charge to a level which turns off IC19/14.

When carrier is initially recognised, monostable IC26/9 is triggered, disablingIC24/11 for a further period of nominally 10ms. Filter R92/C35 prevents glichesappearing on the DCD output due to propagation delay through IC26. The output ofIC24/11 also drives the data carrier detected led – indicating that carrier is beingreceived.

In operation, carrier must be present long enough to complete the pumping sequenceplus the monostable delay before carrier detector is true and the DCD signal isoutput. Once detected, the circuit is insensitive to short breaks in carrier of up to 2 to3 milliseconds, but for longer breaks it turns off without further delay.

10.9 Carrier alarm

In addition to the carrier detected circuit, the output from the receive filter amplifierIC19/1 also drives a peak detector circuit IC18/1, D8, C6. Each positive half cycleof carrier charges C6 to its peak value via diode D8, and this level is compared witha reference voltage derived from R47/R8 ( 2.7V) in comparator IC9/7. If thereceived level falls below the reference, IC9/7 switches high causing the exclusive orgate IC30/3 to switch high and turn ON transistor TR2. This causes the carrier alarmrelay RL1 to operate, and led D6 turns ON to indicate the alarm state.Gate IC30/3 also triggers monostable IC6/6 to produce a nominal 5 second pulse,which maintains the alarm ON for a minimum period of 5 seconds or longer if thecondition remains. A similar detector circuit is formed around D7, C2 andcomparator IC9/1. If the output of receive buffer IC18/7 becomes too high( 12dB above setting up level), comparator IC9/1 switches low and again causesthe alarm condition.

10.10 Auxiliary receive and send circuits

The main receive input also connects to buffer amplifier IC7/7, which providesapproximately 8dB gain before passing the VF signal via a 15dB attenuator– adjustable in 1dB steps, to an output driver circuit for auxiliary equipment.The output circuit may be set for either overall 0dB gain with LK25 in the B positionor +15dB gain with LK25 in the A position.

The driver circuit IC28/7 has a constant current output, which may be used toprovide high impedance greater than 10kΩ, via SK1/5, or if LK24 is fitted it isterminated by R109. This together with barrier transformer T3 and its associatedcompensating components C49, C70 provides a buffered 600 ohm output.Switch SW3-d allows the signal to be diverted into an internal load for test purposes– the levels being monitored on the front panel test points.

28

In a similar manner, an input from some external auxiliary equipment is provided viabarrier transformer T4. This input is buffered by IC27/9, - which provides 8dB gain,before passing through a 15dB attenuator to the combining amplifier IC27/8,previously referred to in Section 10.4.

10.11 External transmit clock

The modem provides a transmit clock, which may be either synchronous orasynchronous to the VF carrier depending upon channel used. For asynchronousoperation, the clock is generated from the baud-rate generator IC12, which runs at64 x baud rate and produces the 115.2kHz clock on output pin IC12/15 used todrive the switched capacitor filters. The required data baud-rate clock of 200, 300,600 or 1200 Hz is selected via LK38, 39, 37 or 36 respectively and is then dividedby 64 in counter IC5. The output from IC5/2 passes via LK28A and buffers IC32/8and IC32/6 to provide the final output.

For synchronous operation, the clock is derived directly from the VF carrierfrequency. Depending upon the ratio of VF frequencies, an output of 2 or 4 x VFfrequency is selected from the outputs of IC23 by one of the links LK12 to18.This drives a shift register, which after a number of clock pulses selected by links LK5-11 causes IC33/9 to toggle. Two division ratios are selected and controlled by gatesIC31/3 and IC31/6, depending upon the state of data input.

For example, at 1500 baud the VF ratio is 1 : 1.5 (1500 : 2250 Hz). The counter,therefore, divides by 2 if the data is logic ‘1’ as controlled by IC31/3 and LK6B, ordivides by 3 as controlled by IC31 and LK11A if the data is logic ‘0’.Toggle IC33/8then divides by 2 to give the effective output ratio of 1 : 1.5 from the initial clockselected by LK12B at 4 x VF frequency.

The external clock is also used to drive toggle IC33/6, which changes state at everydata bit. This output is used as data in the test mode, as selected by SW1/6, andproduces the 010101 test pattern.

10.12 Analogue loopback

Test switch SW2 takes the VF data output from IC7/1, attenuates it by approximately27dB to give the correct receive level and switches it back into the VF Receive inputas a substitute for the normal input. This allows the modem to talk to itself for test andsetting up purposes.

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29


CHAPTER 6

FUNCTIONAL DESCRIPTION


Page 1 of 8


This section describes the operating principles of the MJTW01 intertripping relay,how it carries out its various functions of processing data received and data to betransmitted, the coding techniques used, the conditions under which alarms and tripsare set and the test facilities available.

1.1. Functional overview

An intertripping scheme comprises a pair of equipments with one located at eitherend of the protected zone. The opto-isolated inputs of each equipment are regularlyscanned by the microprocessor. A digital bit pattern is generated according to thestate of the inputs with different patterns being used to indicate whether the tripinputs are set or not. This bit pattern is transferred serially into the modem where itis used to modulate a voice frequency carrier signal. This signal is then transmittedover a suitable voice frequency signalling channel to the equipment at the remoteend.

Upon reception of the voice frequency signals the modem decodes the received voicefrequency signals and transfers the received bit pattern to the controller module.When a complete pattern has been received the integrity of the data is checked by themicroprocessor. If the received message is validated the bit pattern is checkedagainst expected patterns for received tripping commands. The trip outputs are thenswitched accordingly. The transmit and receive codes are user selectable from a listof pre-defined codes which are stored in the relay memory.


Page 2 of 8

Section 2. PROCESSING DATA

Information between the equipment ends is signalled by means of messages. Thesemessages are transmitted and received by an integral modem which provides theinterface between the relay controller module and the voice frequencycommunications circuit.

2.1. Data reception

The modem receives voice frequency signals via the communications link. Itchanges these signals into a bit pattern which is then received and deciphered by themicrocontroller in the controller module.

The incoming data stream is sampled at 8 times the data rate to allow data andtiming information to be extracted. There is a percentage of bit width quality whicheach bit must exceed before it can be accepted. This percentage is 50% in mode 1and 62.5% in mode 2. When a bit has been accepted, a flag is set to signal to the restof the software that a bit is due for processing.

The expected messages are stored as RAM variables which are initialised when theequipment powers up, according to the user settings which are held in a non-volatilememory store. When all the bits of one message have been received, the message iscompared with the expected messages, one by one until a match is found. If themessage does not match any of the expected messages, a communications failurealarm will be set after a certain time. If the message does match, the output logiccontrol causes the appropriate output contacts and leds to operate.

2.2. Frequency shift keying

Before the message is transmitted, the modem changes the bit pattern from themicrocontroller into a voice frequency signal. The messages are transmitted around acertain carrier frequency, given in Section 5.1 of Chapter 2. Each time a 1 is to betransmitted the frequency decreases from the carrier frequency and each time a 0 isto be transmitted, the frequency increases from the carrier frequency. This techniqueof changing frequency is called frequency shift keying.

2.3. Data transmission

There are three optically isolated inputs which can be energised, trip 1, trip 2, and inmode 1, the test input. Different messages will be transmitted depending on whichinputs have been detected (or in the case of mode 2, if a test mode has been entered,by pressing the test key). The inputs are scanned and the appropriate coded messagesare pulled from RAM and transmitted one bit at a time. The relevant leds areilluminated and the bit pattern is sent over the communications link to the equipmentat the other end.


Page 3 of 8

2.4. Output logic control

There are five different relay outputs which can be operated by the software, namely,commfail, schemefault, trip 1, trip 2 and test.

Commfail is operated if meaningless messages or no messages at all are received forlonger than one second. Schemefault is operated at the same time as acommunications failure, and also on its own when the equipment is taken out ofservice if the operator interface is invoked, or a software or processor failure isdetected, or a failure of the auxiliary power supply occurs. Trip 1, trip 2 and test areoperated when these conditions are detected. The data being received causes flags tobe set and when the condition is confirmed the outputs are operated correspondingly.See Section 5 for further details.

2.5. Manchester encoding

This is a coding technique for bit patterns which gives extra transmission security. Iteffectively doubles the message length and as a message will not be accepted unlessevery single bit is verified, ensures more security. The longer the message is thelonger the transmission time for each message. Manchester coding may be defined aseach bit sent along with its complement ie. a data 1 transmission is followed by a 0,and a data 0 transmission is followed by a 1. See Figure 1 for illustration.

Message fragment

V 1 0 0 1

Manchester encoded fragment of the message :

1 1 1 0 0 1 0 1 1 0

Figure 1 Example of Manchester encoding

2.6. Message format

2.6.1. Mode 1

The message is Manchester encoded, but only half the bits need to be stored as everysecond bit is the complement of the last bit. These bits are stored in a 3 byte register.The first bit is a violation bit such that when Manchester Encoded there are two 1'sin succession. The next two bits make up the start of the message, which is called the'sync' or synchronisation bits. This is followed by the identification channel code (5bits), the trip 1 message (5 bits) and trip 2 message (5 bits). The last 8 bits are theparity check and these are calculated after 16 bits have been counted.


Page 4 of 8

The trip codes start with a marker, T, which is 1 if there is a trip and 0 otherwise.This leaves four bits for the trip codes. In the idling state when no trip data is beingtransmitted, the channel identity is transmitted and the trip 1 and trip 2 patterns areboth 00000.


When the remote loop testing feature is required, the channel identifiers are arrangedas seven pairs with one bit of the identifier being used as an odd/even marker for testor normal modes. The following only holds when a special test code has beenselected for the channel identifier field pattern ie. '1t' to '7t'. The test marker is thenthe least significant bit of the channel ID. code, and can be used to switch from theeven to the odd address codes. For example, address code '1t' is equivalent to addresscode '2' (0010) when the test input is not energised, but address code '3' (0011) willbe transmitted when the test input is energised.

If there is no data carrier detect (DCD) signal from the modem, the message isdeemed invalid. Otherwise, the program will go on to look for a synchronisationcharacter (sync). The sync is found by searching for three 1's, followed by a zero ie.the two violation bits and then a 1 and a 0 is at the start of every message.

At the end of a message, at a bit count of 24 (excludes violation bit) the parity bitsare checked to see if these have been received correctly. If the parity bits are thesame as the parity bits calculated by the receiver, the received message is applied eg.operate the output contacts etc.

violation synccode

channel id trip 1 code trip 2 code parity check

V 1 0 X X X X T X X X X T X X X X P P P P P P P P

Figure 2 Mode 1 message coding


Page 5 of 8

2.6.1.1 The parity check

The data for the parity byte may be considered as coefficients of a polynomial. Theparity generator divides the data polynomial by x8 + x7 + x5 + x4 + x + 1 leavingthe remainder in the parity store, to be transmitted at the end of the data as the checkcharacter. Thus at the receiving end, if the operation is repeated, the polynomial(data and parity) will divide exactly leaving zero in the parity store - providing notransmission errors have occurred.

In practice this is carried out by using the following 8 x 16 matrix parity for thepolynomial

x8 + x7 + x5 + x4 + x + 1 :

1 1 1 0 1 0 1 1 1 0 0 1 0 0 0 1 1 2 1 0 1 1 1 1 0 0 1 0 1 1 0 0 1 0 3 1 1 0 1 1 1 1 0 0 1 0 1 1 0 0 1 4 0 0 1 1 1 0 0 0 0 0 0 0 1 1 1 1 5 1 1 0 0 1 0 1 1 0 0 1 0 0 1 0 0 6 1 1 1 0 0 1 0 1 1 0 0 1 0 0 1 0 7 1 1 1 1 0 0 1 0 1 1 0 0 1 0 0 1 8 1 0 1 0 1 1 1 0 0 1 0 0 0 1 1 1

To calculate the parity for the following bit pattern :

0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0

Take the columns from the matrix corresponding to the 1's in the pattern, add themand the modulo (ie. divide by two) remainders of each individual addition make upthe 8 parity bits.

8 7 6 5 4 3 2 10 1 0 0 1 1 0 01 0 0 1 1 1 1 01 1 1 0 1 0 1 0 +0 0 1 1 1 0 0 0 = 8 bit parity byte

2.6.2 Mode 2

The message format for mode 2 is completely different to that of mode 1. See Figure3 below. It contains only 15 bits. This is because there is no parity checking at theend and the message is not Manchester encoded. It has instead, 4 synchronisationbits dictating the message start, three 0's and a 1. This is followed by a one for amonitor code, and a 0 for a trip code. Then there are 10 bits devoted to one of threemessages: monitor (no trip), trip 1, or trip 2.

A data carrier detect must be present for the bits to be processed. A trip message isonly acted upon if monitor codes have been received for user programmable time(0.1 s - 0.4 s) prior to this. If the received bits match one of the expected codes the


Page 6 of 8

relevant trip flags are set or cleared, the communication failure flag is cleared andthe communications failure timer is reset. If there are no valid messages for aduration of one second, the communications failure timer times out and thecommunications failure output is operated.

sync code trip marker 10 bit code for : Monitor,trip 1 or trip 2

0 0 0 1 T X X X X X X X X X X

Figure 3 Mode 2 message coding


Page 7 of 8

Section 3.TRANSMISSION TIMES

3.1. Transmission time

The transmission time of a teleprotection channel is the time elapsed between themoment of change of state at the transmitter input and the moment of thecorresponding change of state at the receiver output excluding propagation time.

The maximum transmission times for the relay are tabled below.

3.1.1. Mode 1 transmission times


Single trip 100 600


Single trip 55 1200


3.1.2. Mode 2 transmission times


Single trip 45 600

Two simultaneous trips 45 for the firsttrip and 70 forthe second

600

Single trip 25 1200

Two simultaneous trips 25 for the firsttrip and 40 forthe second

1200


Page 8 of 8

Section 4.INPUT FUNCTIONS

There are two standard rear MIDOS connectors at the back of the relay. There arefour inputs, one for the auxiliary power supply and three optically isolated inputs forinitiating test and trip commands. These are numbered as seen on the externalconnection diagram, Addendum. The controller module consists of four variants, asgiven in Chapter 1, Section 2 on relay identification, and care must be taken not toexceed the module's voltage range.

4.1. Power supply input

The equipment will not carry out its functions unless the correct terminals on theMIDOS rear connectors have been energised with the appropriate power supply forthe controller module.

4.2. Trip 1 input

This input initiates the transfer of a trip 1 command. The energised signal inputcauses a message containing a trip 1 code to be transmitted to the intertripping relayat the far end. In mode 2 only, the trip signal is boosted by 3dB.

4.3. Trip 2 input

This input initiates the transfer of a trip 2 command. The energised signal inputcauses a message containing a trip 2 code to be transmitted to the intertripping relayat the far end. In mode 2 only, the trip signal is boosted by 3dB.

Note: In mode 2, if the two trip inputs are energised simultaneously, the secondtrip message is sent immediately after the first and the operate time isincreased to approximately 1.667 times the first trip time. If this eventoccurs in mode 1, both trip codes are sent in the same message andconsequently both trips are transferred in the normal operate time.

4.4. Test input

NB. This input signal will only be valid when the equipment is in mode 1.

If a test is required, the user may energise this opto-isolated input by using theappropriate voltage supply. The test signal will be ignored unless a test code hasbeen programmed into the transmit ID code. This simply means the relay is enabledto perform a test if it is required to do so. An energised test signal will cause a testmessage to be sent to the intertripping relay at the remote end. The test led andoutput contacts of the relay at the remote end will operate upon reception of the testmessage. Any trips received or trip inputs energised, while a test is under way, willbe dealt with in the normal fashion.


Page 9 of 8

Section 5.OUTPUT CONTACT FUNCTIONS

There are four pairs of normally open trip 1 output contacts, four pairs of normallyopen trip 2 output contacts, and two pairs of normally open test contacts. There aretwo pairs of normally open communication failure contacts and one pair of normallyclosed scheme fault contacts. These output contacts must be wired according to theexternal connection connection diagram Addendum and/or the scheme diagram.

5.1. Trip 1 output


5.2. Trip 2 output


5.3. Test output

The control of the test output varies according to whether the relay is configured foroperation in mode 1 or mode 2.

Mode 1:

If the MJTW01 relay receives a message containing a test marker via itscommunication link from the MJTW01 at the other end, it closes its test outputcontacts and the test led illuminates, only if its receive ID code is programmed witha test code. The test message is not reflected back to the other relay, unless the userchooses to wire the test output back into the test input and send a test message backin that manner. This has a flexible application and can be used for the transfer of anextra command if required.

Mode 2:

If the test key is pressed in this mode of operation, the local relay closes its testcontacts and its test led. illuminates. The relay will transmit the expected receivemonitor code instead of the normal transmit code while the test is in progress. Thisallows a communications loopback to be applied for fault finding on thecommunications link. Any trip will be received as normal but a trip input at thisstage will be ignored, and no trip message will be transmitted.

5.4. Communication failure output

If the MJTW01 relay receives a message via its communication link from theMJTW01 at the other end, which it does not recognise, the communication failureoutput contact will close if messages are not getting through correctly for several


Page 10 of 8

reasons. In mode 1 these reasons are, if there are no messages understood for morethan one second, if there is carrier detect failure, or a manchester violation, or aparity failure, or a channel ID failure. In mode 2 the reasons are, if there are nomessages for more than one second or, if a trip has been received before a monitorcode has been received, for a user-programmable (function setting 5, F5) length oftime.

5.5. Scheme fault output

This is a normally closed contact which is held open throughout the operation of theequipment and closes in the event of a communications failure, a software failure, orif the power supply is lost, or if the user has invoked the operator interface.

If the power supply is lost, the scheme fault output contact will operate but the ledwill not illuminate.


CHAPTER 7

SOFTWARE DESCRIPTION

MJTW01 R 8124SERVICE MANUAL Chapter 7

Page 1 of 9


This section describes the embedded software of the MJTW01 intertripping relay. Itcan be divided up into different parts namely initialisation, receiving andtransmitting data, control logic and operator interface software.

Section 2. PROCESSING SOFTWARE

Having decided which mode the equipment is in, and initialised the rest of thevariables, the real-time software is split into three broad functions which are carriedout simultaneously. These functions are the receive and transmit parts of theprogram, the flowcharts for which can be found in Figures 4 and 5. Operating theoutput contacts is another important part and this is done just before the data istransmitted. Also, the operator interface is run as an out of service routine, the menusoftware is invoked when the real-time software sees a keypress.

2.1 Initialisation

Under the control of a 1ms timer interrupt, the relay settings are read from the non-volatile EEPROM store. The values returned are checked to ensure that they arewithin the valid ranges. If any are out of range then an error is reported via theoperator interface, see Section 4 of Chapter 8. The liquid crystal display (lcd) andlight emitting diodes (leds) are initialised. If there is no erroneous setting dataretrieved from the EEPROM chip, the communications failure and scheme faultoutputs and leds are set and the intertripping software is activated.

2.2 Interrupts

The processing of received data is a background task which is carried out in themain software loop. It is interrupted by the other tasks which run on the 8051'sinterrupt system. There are three interrupts utilised by the software, one external andtwo internal timers :

– transmit clock interrupt (txcint),– a timer based on this external transmit clock interrupt from the modem and– a 1ms timer interrupt.

The first two interrupts are used exclusively by the intertripping software and the1ms timer interrupt is used on initialisation of the software and when the operatorinterface is invoked.


Page 2 of 9

2.2.1 External transmit clock interrupt (txcint)

This is driven by an input signal from the modem through port pin P3.3, anddepends on the baud rate (either 1200 or 600) of the modem. At 1200 Baud, the timeinterval between interrupts is 0.832ms and at 600 Baud, this is 1.672ms.

i.e. 1/1200 bits/s = 0.833 x 10-3 s

This interrupt controls the timing of the real-time software functions. The period ofthe transmit clock interrupt is measured and is used to initialise a timer interruptwhich controls the reception of data (ie. a receive UART function) from the modem.The transmit clock interrupt controls the transmission of data, the led statusinformation, the timing and control of the relay outputs, the scanning of inputs andthe maintenance of a watchdog timer.

2.2.2 Internal timer

The internal timer is based on the external transmit clock interrupt from the modem.It occurs in fact, eight times as often as the Baud rate. This is because every time abit is received, it is sampled 8 times to check its bit width quality. When theequipment is online, this interrupt triggers the watchdog which ensures the processordoes not get reset.

2.2.3 1ms timer interrupt.

When the equipment is out of service, and on initialisation, this interrupt triggers thewatchdog which ensures the processor does not get reset. It also deals with readingand writing to the EEPROM, and other monitor routines which are used for testing.It is disabled while the other two interrupts control the intertripping software.

See graphs of the interrupts Figures 1 and 2 below.

time

833µs

1/8 1200 baud

500µs

1200 baud

1000µs

1ms monitor

Figure 1 Graph of the microprocessor interrupts in 1200 baud


Page 3 of 9

time

. . . . . . . . . . . . . . .

500 µs

1/8 600 baud

600baud

1000 µs

1msmonitor

Figure 2 Graph of the microprocessor interrupts in 600 baud

2.3 Data reception

The incoming data stream is sampled at eight times the data rate such that, in effect,each data bit received is sampled eight times. There is a percentage of bit widthquality which each bit must exceed before it can be accepted. This percentage is50% in mode 1 and 62.5% in mode 2. When a bit has been accepted, a flag is set tosignal to the rest of the software that a bit is due for processing. Here is a briefdescription of the process.

The expected messages are stored as RAM variables which are initialised when theequipment powers up. When all the bits of one message have been received, themessage is compared with the expected messages, one by one until a match is found.If the message matches with one of the expected messages, the output control logiccauses the appropriate output contacts and leds to operate. If the message does notmatch with any of the expected messages, a communications failure alarm will beset after a certain time. See flowchart Figure 4.

2.4 Data transmission

Three inputs can be set, trip 1, trip 2, and in mode 1, the test input. Differentmessages will be transmitted depending on which input has been detected, (or in thecase of mode 2 if a test mode has been entered by pressing the test key). The inputsare scanned and the appropriate coded messages are pulled from RAM andtransmitted one bit at a time. The relevant leds are illuminated and the bit pattern issent over the communications link to the equipment at the other end. See flowchartFigure 5.

2.5 Output logic control

There are five different outputs which can be operated by the software, namely,commfail, scheme fault, trip 1, trip 2 and test.

Commfail is operated if messages are not getting through correctly for severalreasons. In mode 1 these reasons are :

– if there are no messages understood for more than one second,– if there is carrier detect failure,


Page 4 of 9

– if there is a Manchester violation,– if there is a parity failure,– if there is a channel ID. failure.

In mode 2 the reasons are :

– if there are no messages for more than one second– if a trip has been received, before a monitor code has been received for a certain

length of time. This time is determined by function setting 5.

Scheme fault is operated at the same time as the communications failure, and on itsown when the operator interface is invoked or the relay is faulty.

Trips 1 and 2 and test are operated when these conditions are detected by thesoftware. The data being received causes flags to be set and when the condition isconfirmed the contacts are operated correspondingly.


Page 5 of 9

Section 3. MENU SOFTWARE

The operator interface is made up of a keypad, 7 light emitting diodes (leds), and aliquid crystal display (lcd). When the user wishes to view or change settings, a keymust be pressed and the equipment is brought out-of-service. In this condition, it isnot performing its intertripping duties until the 'restore' key is pressed and theequipment is brought online again. The key pad is scanned periodically for a keypress. This is done by scanning the sense lines on the hexadecimal keypad anddetecting a key press from one of 4 keys only in mode 2 and one of three keys onlyin mode 1.

The software for the operator interface is divided into five main sections, one sectionfor each key pressed, and one for error detection. The keypad has 16 keys on it, butonly four of these will invoke the menu software initially - 'test', 'step', 'code setting',or 'function setting'. Any other keypress will be ignored at this stage. The menusoftware that is called sets up the 1ms interrupt required (see Section 4.1 oninterrupts), disables the two intertripping software interrupts and turns off allcontacts and leds except for the scheme fault which is used to indicate the equipmentis offline. The 1ms interrupt controls the software timing of the menu software andalso maintains functions such as input strobing and watchdog triggering. One of thesections to be entered is then selected by creating a different mode for each one -these are detailed in the following sections.

The position of the user in the menu software can be identified using the mode andlevel attained. There are 4 levels as illustrated by Figure 3 below.

Offline

Test Code FunctionStep

number restore func code restore number

restore step code function restore step code function

test/reset enter restore test/reset enter restore

Figure 3 Structure of the operator interface software


Page 6 of 9

There are six different 'modes' in which the software can be run:

Mode Description

error lcd displays error number

step displays list of current settings

func allows change to function setting

code allows change to code setting

test mode 2 test mode

online restore to service

3.1 Error mode

It is unlikely that any errors would occur in the initialisation of the variables but hereis a description of how the software deals with them if they should occur.

On initialisation, the EEPROM registers are read and each value is checked to see ifit falls into the correct range for that setting. Each time an out of range error isdetected, a number is reflected back onto the lcd The user can look up the error listand identify the setting and correct it using the keypad facilities. Additionally, thesoftware checks for a correct modem and reports an error if the modem is notconnected. In this case, the error is cleared by connecting the correct modem and re-applying the power.

If any errors have been found by the time all of the EEPROM registers have beenread and checked, the software goes out of service automatically and enters'error_mode' which displays the first error message. An error message is reported tothe lcd in the form "err x", where x is a number which uniquely identifies the error.

Each subsequent press of the 'step' key, displays the next error. See error list Section4.1 of Chapter 8. The first errors are related to the modem connection. The othererrors refer to the EEPROM registers which may be out of range. This could be dueto some form of data corruption and can readily be rectified by the user through theoperator interface.

3.2 Step mode

Bringing the equipment out of service using the step key causes the first setting on alist of current settings to be displayed on the lcd. Each ensuing press of the step keyfrom this starting point, displays each subsequent setting on the current setting list,in turn. At the head of this list, the current state of the opto-isolated inputs trip 1, trip2 and test is displayed. At the end of the code and function setting list, the softwarereference number is displayed and then the word 'finish'. Pressing the step key againcauses the list to wrap around and the first setting is displayed again.


Page 7 of 9

The second function of the step key comes into play when changing the settings butthis time the software is not in 'step_mode'. There are two types of setting, code andfunction settings which amount to 12 different settings. The user has a further optionon the value of each of these settings and these values are held in code memory(EPROM chip), until a setting is changed. These settings can be stepped throughusing the step key while in 'code_mode' or 'func_mode', see Sections 3.3 and 3.4 onthese modes.

3.3 Code mode

This is entered when the 'code' key is pressed. A software module is entered initiallywhich causes the lcd to display "C..." and then looks for another keypress. A certainsequence of key presses will keep the software in code_mode. Each time a key ispressed a new level is entered on the operator interface. This helps the software tokeep track of its position while the relay is out of service. For instance if the userwished to change the value of a code setting, this is how it would be done.

Key press Level Action

Code setting 0 "C..." on lcd

Number between 1 and 7,say '3'

1 "C3 7t" on lcd

Step

Step (again) etc.

2 "C3 1" on lcd

"C3 2" on lcd etc.

Enter 3 "C3 2" flickers off and then onagain and the new value for thefunction setting is stored in theEEPROM chip

Restore --- Restores relay to service - now inservice again with the new settings

If the user does not wish to 'enter' a new setting after all, the procedure can beabandoned at any time by pressing a different key other than 'enter' such as 'restore'.

When a number is pressed in the above sequence, the code setting required isdisplayed on the lcd. The software then awaits another keypress. If the 'step' key isthen pressed, the software displays the next value of the code setting which couldtake the place of the current setting. Again the program looks for the next key press.If this is 'enter', the new value of code setting is written into the appropriate registerin the EEPROM chip.

The software ignores any keypress activity which is not expected, for instancepressing the 'step' key when the lcd displays "C...".

3.4 Func mode


Page 8 of 9

This is operated in a very similar manner to that of code_mode, except that functionsettings are the issue instead of code settings. Func_mode is entered when the'function setting' key is pressed. Again, the software module is entered initiallywhich causes the lcd to display "F..." and then looks for another keypress. A certainsequence of key presses will keep the software in func_mode, just as in code_mode(see Section 3.3).


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3.5 Test mode

Test_mode is only applicable when the relay is in equipment mode 2.

Pressing the test/reset key when the relay is online and performing its normalintertripping functions has a different effect to that of pressing it while alreadyoffline.

From online:

Pressing the 'test/reset' key invokes a test condition in mode 2. This is carried outwhen it is desirable to check the communications link from one end only. Usually asend and a receive code will be different on one end to avoid cross link errors. It ispossible with the test facility to make these two codes temporarily the same. Then aloopback connection can be put across the send and receive lines of the modem forinstance, so the relay can communicate with itself.

When the 'test' key is pressed, a testout flag, the test output and the test led are set.The software then returns to an online mode. When the software is running in thismode and sees the testout flag is set, the expected receive monitor code istemporarily transmitted in place of the transmit monitor code. If the test key ispressed a second time, the testout flag, the test led and the test output are cleared andthe transmit code is sent as normal.

From offline:

Pressing the 'test/reset' key invokes a reset condition no matter if the relay isconfigured for operation in mode 1 or mode 2. This is used when the operator hasstepped down through some of the values for a particular setting, and wishes toreturn to the initial value. Pressing reset will cause the display to show the initialvalue.

This can only occur when the software is at level 2 ie. step has been pressed to stepthrough settings from an already offline condition. The original value of the requiredsetting will then be displayed.

3.6 Online

When the 'restore' key is pressed from any position in the menu software, the modeis changed to 'online'. Once this mode has been detected by the software, theinitialisation module is called to re-initialise the interrupts, timers and variables andrun the normal intertripping software.


CHAPTER 8

OPERATING INSTRUCTIONS


Page 1 of 10


The installation and handling procedure in Chapter 3, should be read beforeattempting to operate the MJTW01. This section explains the use of the operatorinterface of the MJTW01 intertripping relay. In order to gain access to the operatorinterface the door must be unlocked and opened. The interface consists of a sixteenkey keypad, a seven segment, eight character liquid crystal display and seven lightemitting diodes. See Figure 1 below.

INDEX VALUE

restorestep enter

test

reset

code

functrip 1 send

trip 1 receive

trip 2 send

trip 2 receive

test

comms fail

scheme fault

1 2 3

4 5 6

7 8 9

0

Figure 1 Keypad, leds and liquid crystal display

Section 2. MENU SYSTEM EXPLAINED

There are twelve settings on the equipment which may be changed by the user, viathe operator interface. The value of each of these settings is held in a register in theEEPROM chip, which holds this information safe in the event of a power supplyfailure. If a value is changed, the new value is written to the appropriate register inthe EEPROM instead. When the equipment is first powered up, this non-volatilechip will hold the default settings. These may be changed to other settings using thechoice given by the operator interface. A list of the setting indices and correspondingnames is given on the inside of the door of the case. This form of cross reference isused as there is a limit to the number and type of characters which can be displayed


Page 2 of 10

on an 8 character 7 segment lcd. The following explains exactly what can be donewith the operator interface and how to carry out any changes to the user-programmable settings.

2.1. Invoking the operator interface

If the equipment is in mode 2, the operator interface may be invoked by pressing oneof four keys on the keypad ie. 'function setting', 'code setting', 'test', or 'step' keys. Ifhowever, the equipment is in mode 1, only the three keys 'function setting', 'codesetting', or 'step' apply. This is because the test facility differs in modes 1 and 2. Ifone of these keys is pressed, the equipment is taken out of service, the scheme faultled will illuminate, the scheme fault output contact will close, and any other outputcontacts and leds will be extinguished. The remote end equipment will register acommunications failure and scheme fault when this is carried out. The equipmentcan be restored to service at any time by pressing the 'restore' key. Care must betaken when restoring the equipment to service, that the settings will be understood bythe equipment at the far end of the communication link. The receive code on oneequipment for instance, must be the same as the transmit code on the otherequipment or they will be unable to communicate correctly.

2.2. Viewing the settings

The settings may be viewed each in turn by pressing the step key when the equipmentis in service. This brings the equipment out of service, and displays the current statusof the trip 1 input. Pressing the step key a second time displays the current status ofthe trip 2 input and a third time the test input. To view the next setting simply pressthe step key again. Then the code settings can be displayed one by one, followed bythe function settings. Finally the software reference number is displayed and then theword 'finish' indicates the end of the list. When the end of the list is reached, furtherpresses of the step key will cause the list to wrap around and the first setting will bedisplayed again and so on.

NB. The setting list may only be viewed in this manner if the step key is pressedwhile the equipment is still in service. If the step key is pressed at any othertime while the operator interface is invoked it has a different function (seeSections 2.3 and 2.4)

2.3. Code settings

There are seven code settings in either modes 1 or 2. In mode 1, these correspond tothe codes of the Teleprotection equipment which the MJTW01 has been designed toreplace, and which were implemented through switches on the Teleprotectionmodules.

When changing the mode of operation from 1 to 2 or vice versa, the default code andfunction settings for that mode are programmed automatically into the relay. Anychange being made to the other settings must therefore be made after the modechange has been entered.


Page 3 of 10

The message formats for both modes 1 and 2 are given in Sections 4.2 and 4.3 of theapplications chapter in this manual. These sections are in fact repeated here for thesake of the completeness of this chapter.

2.3.1. Message format for mode 1

In mode 1, the message format includes 2 start bits or synchronisation bits, theidentification channel code (4 bits), the trip 1 message (5 bits) and trip 2 message (5bits). The last 8 bits are the parity check and these are calculated after 16 bits havebeen counted.

The trip codes start with a marker which is 1 if there is a trip and 0 otherwise.

This leaves four bits for the trip codes. In the idling state when no trip data is beingtransmitted, the channel identity is transmitted and the trip 1 and trip 2 patterns areboth 00000.


When the remote loop testing feature is required, the channel identifiers are arrangedas seven pairs with one bit of the identifier being used as an odd/even marker for testor normal modes. The following only holds when a special test code has beenselected for the channel identifier field pattern i.e. '1t' to '7t'. The test marker is thenthe least significant bit of the channel ID. code, and can be used to switch from theeven to the odd address codes. For example, address code '1t' is equivalent to addresscode '2' (0010) when the test input is not energised, but address code '3' (0011) willbe transmitted when the test input is energised.

2.3.2. Message format for mode 2

The message format for mode 2 is completely different to that of mode 1. There areonly 15 bits per message as there is no parity check at the end. As well as this, themessage is not Manchester Encoded. It has instead, 4 synchronisation bits dictatingthe message start, three 0's and a 1. This is followed by a 1 for a monitor code and a0 for a trip code. Then there are 10 bits devoted to one of three messages: monitor(no trip), trip 1, or trip 2.

A list of all the possible monitor and trip codes are given as follows :


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2.3.2.1 Message codes for mode 2

Codenumber

Monitor codes Trip codes

1 0 0 0 1 1 0 1 1 1 0 0 1 1 1 0 0 0 0 1 0 1 0 1 0 1 1 0 0 0 02 0 0 0 1 1 1 0 1 1 1 1 0 1 0 1 0 0 0 1 0 1 0 0 1 0 0 1 1 0 03 0 0 0 1 1 0 1 1 1 0 1 1 0 1 0 0 0 0 1 0 1 0 0 1 0 1 1 0 0 04 0 0 0 1 1 1 1 1 0 1 0 0 0 1 1 0 0 0 1 0 1 0 0 0 1 0 0 1 0 15 0 0 0 1 1 1 0 1 1 0 1 0 1 1 0 0 0 0 1 0 1 0 1 0 1 0 1 0 0 06 0 0 0 1 1 1 0 1 1 1 1 1 0 0 1 0 0 0 1 0 1 0 0 0 0 1 0 1 0 17 0 0 0 1 1 1 0 1 1 1 0 1 1 0 1 0 0 0 1 0 1 0 0 1 0 0 1 0 1 08 0 0 0 1 1 1 1 1 0 1 1 0 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 19 0 0 0 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0 1 1 010 0 0 0 1 1 1 1 1 0 1 0 1 0 1 1 0 0 0 1 0 1 0 0 1 1 0 0 1 0 011 0 0 0 1 1 1 1 1 0 0 1 1 1 1 0 0 0 0 1 0 0 1 0 0 1 0 1 0 1 012 0 0 0 1 1 1 1 1 0 1 0 1 1 0 1 0 0 0 1 0 0 1 0 0 1 1 0 0 1 113 0 0 0 1 1 1 1 1 0 0 0 1 1 1 1 0 0 0 1 0 0 1 0 0 1 0 0 1 0 114 0 0 0 1 1 1 1 0 1 0 0 1 1 1 1 0 0 0 1 0 0 1 0 1 0 1 1 0 0 015 0 0 0 1 1 1 1 1 1 1 0 1 0 0 1 0 0 0 1 0 0 1 0 0 1 0 0 1 1 016 0 0 0 1 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 0 1 0 0 1 0 1 0 0 117 0 0 0 1 1 1 1 1 1 1 1 0 0 1 1 0 0 0 1 0 1 0 1 0 0 1 0 1 1 018 0 0 0 1 1 1 1 1 0 0 1 1 0 1 1 0 0 0 1 0 0 1 0 0 1 1 0 1 0 119 0 0 0 1 1 1 1 1 0 1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 1 120 0 0 0 1 1 1 1 1 0 1 0 0 1 1 1 0 0 0 1 0 0 1 0 0 1 0 1 1 0 0

Here is a list of the code settings, a brief description of each for both modes 1 and 2,and the values of the default settings.

IndexCode

DescriptionMode 1

DescriptionMode 2

C1 Equipment mode of operation


Equipment mode of operation



Page 5 of 10

IndexCode

DescriptionMode 1

DescriptionMode 2

C2 Transmit channel ID code -

The identification code istransmitted first as part of thewhole message. There are 22channel ID codes, including 7test codes. The same choice ofcodes are given in both thetransmit and receive codes.

Transmit monitor code -

In mode 2, the message beingtransmitted on any onechannel is either a trip codeor a 'no trip' code ie. amonitor code. There are 20monitor codes. These are thesame in both transmit andreceive codes.

C3 Receive channel ID code -

At the receiving end this ID ischecked and validated. There arethe same number of receivecodes as transmit codes.

Receive monitor code -

In mode 2, the message beingreceived on any one channelis either a trip code or a 'notrip' code ie. monitorcode.










Page 6 of 10

IndexCode

DescriptionMode 1

DescriptionMode 2










Page 7 of 10

2.4. Function settings

A similar routine is followed to change the function settings as is for the codesettings. There are five function settings as described in the following list, and thedefault setting for each is given.

IndexCode

DescriptionMODE 1 and MODE 2

F1 Minimum trip output contact closure time -This is the minimum time for which the trip output contactswill remain closed once a trip command has been received.Values from 0.1 to 0.4 seconds can be selected in steps of 0.1seconds.

F2 Action of trip 1 output contacts under communication failureconditions -If a communications failure condition occurs during a trip, theaction of the trip outputs can be user programmed to hold thetrip output contacts as they are, or to reset them to theirnormally open state.

F3 Action of trip 2 output contacts under communication failureconditions -Same as F2, but acting on trip 2 instead.

F4 Minimum communications failure alarm output contactclosure time -This is the minimum time for which the communication outputcontacts will remain closed, once a communication failure hasoccurred. Values from 0.1 to 0.4 seconds can be selected insteps of 0.1 seconds.

F5 Communication failure output contacts reset time -This is the time delay between the recognition of the re-establishment of the communication link, and the clearance ofthe communication alarm output contacts. Values from 0.1 to0.4 seconds can be selected in steps of 0.1 seconds.

2.5. Changing the settings

The following sequence of key presses shows how code setting 3, say, may bechanged from a value of 7t (the default value) to a value of 2, and subsequently howa function setting 4 can be changed from its default value of 0.2 s to 0.1 s. Whenchanging from mode 1 to mode 2 and vice versa, the default values for that mode areautomatically programmed into the relay, so always change the mode if required todo so, before changing the other settings.


Page 8 of 10

Key press Sample Action

Code setting "C..." displayed on lcd

3 "C3 7t" on lcd

Step

Step (again) etc.

"C3 1" on lcd

"C3 2" on lcd etc.

Enter "C3 2" flickers off briefly, and then onagain and the new value for the code settingis stored in the EEPROM chip

Function setting "F..." displayed on lcd

5 "F5 0.2" on lcd

Step

Step

Step

"F5 0.3" on lcd

"F5 0.4" on lcd

"F5 0.1" on lcd

Enter "F5 0.1" flickers off briefly, and thenon again and the new value for the functionsetting is stored in the EEPROM chip

Restore Restores relay to service - now in serviceagain with the new settings

The different function of the step key can now be seen - it is used to step through theavailable values for a single setting at a time. The enter key causes the new settingvalue to be written to the EEPROM register. If the enter key is not pressed, thesetting value will not be changed.

2.6. Effect of the reset key

Having stepped through the available values when carrying out a setting change, theoriginal value may be displayed again by pressing the 'test/reset' key whence thesetting will be reset. If the reset key has been pressed, the operator must start theprocess again if a setting change is still required, by pressing the 'code setting' or'function setting' key.

2.7. Test input action

2.7.1 Mode 1

A test can only be carried out if the transmit ID code has a test code as its setting,and the receive ID code at the remote has the same test code. The opto-isolated testinput (see external connection diagram Addendum) must then be energised to eithera


Page 9 of 10

24/54 V range or 110/125 V range, depending on the module voltage (see Chapter 4Section 2.2.2). The test contacts and the test led will operate on the equipment at theremote end, to show a test is being carried out over the entire intertripping system.

2.7.2 Mode 2

NB. The mode 2 test function can only be activated when the equipment is online, performing its normal intertripping function.

Pressing the 'test/reset' key invokes a test condition in mode 2. The test contacts willclose and the test led will illuminate to show a test is in progress. This is carried outwhen it is desirable to check the communications link from one end only. Usually asend and a receive monitor code will be different on one end to avoid cross linkerrors. The test facility makes these two codes temporarily the same, withoutchanging the code setting values. Then a loopback connection can be put across thesend and receive lines of the modem so it can communicate with itself.

If the test key is pressed a second time, the test is cancelled, the transmit code is sentas normal and the test led is extinguished and the test output contacts open.

Section 3. OUTPUT CONTACTS AND LED INDICATIONS

Please refer to the external connection diagram Addendum, and the keypad diagram,Figure 1 Section 1, throughout this section.

Each time a 'trip 1 receive', 'trip 2 receive', 'test', 'comms fail' or 'scheme fault' ledilluminates on the keypad, the corresponding contacts will close .

3.1. Output contacts

There are four pairs of normally open trip 1 output contacts, four pairs of normallyopen trip 2 output contacts, and two pairs of normally open test contacts. There aretwo pairs of normally open communication failure contacts and one pair of normallyclosed scheme fault contacts. These output contacts must be wired according to theexternal connection diagram Addendum and/or the scheme diagram.

3.2. Leds

There are seven leds on the keypad of the drawout module. These may also be seenfrom the outside of the case with the door closed. They include 'trip 1 send', 'trip 1receive', 'trip 2 send', 'trip 2 receive', 'test', 'comms fail' and 'scheme fault'.

So, for example, if a fault on a power line causes a trip 1 input to be energised, and atrip 1 message to be sent to the remote end of the communications link, the 'trip 1send' led will illuminate. At the remote end, the 'trip 1 receive' led will illuminate andthe trip 1 output contacts will close.


Page 10 of 10

The test led and output contacts will operate in mode 1 if there is a test messagereceived from the remote end, and in mode 2 if the test key is pressed while theequipment is in service.

The communications led and output contact will be activated if there is breakdown incommunication between the two ends for any reason.

The scheme fault led and output contacts will operate automatically in the event of acommunications failure, a software or a processor failure, if the power supply is lost,or if the user has invoked the operator interface. If the power supply is lost, thescheme fault led will not illuminate, but the contact which is held open throughoutnormal operation of the equipment, will close.


Page 11 of 10

Section 4. ERROR MESSAGES

Error checking is only carried out when the processor is initialised on a power upcondition. In the unlikely event of an error message occurring on the lcd, check theerror list to see what the problem is and take appropriate action to solve the problem.See Chapter 10 on fault finding. The relay checks for the presence of a modem bymonitoring a transmit clock input. If a valid input is not received from the modem,an error is reported. Errors 1 and 2 involve connecting the correct modem, either a600 or 1200 baud channel, to the drawout module with the auxiliary power supplyremoved. This is supplied as part of the equipment and is already connected, so thereshould not be any problem, unless one of the modules is removed.

Errors 3 to 15 indicate an out of range value in a setting field. If the operator choosesto view the erroneous setting, the setting field will be displayed as blank on the lcd toindicate the error. This can be corrected by using the operator interface to change thesetting to one of the available values, as explained in Section 2.3. Finally, error 16indicates that the operator interface was in use when the equipment lost its powersupply. Ensure that the settings are as they should be by pressing the 'code setting'key and each of the numbers from 1 to 7, and then the 'function setting' key and theeach of the numbers 1 to 5. Press the restore key to return the equipment back toservice.


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4.1. Error list

Indexnumber

Setting* Problem

1 ___ Modem is not connected2 ___ Incorrect modem baud rate3 C1 Out of range - value must be 1 or 24 C1 Out of range - value must be 1 or 25 C2 Value must be between 1 and 15 or 1t and 7t in mode 1, and

between 1 and 20 in mode 2.6 C3 Value must be between 1 and 15 or 1t and 7t in mode 1, and

between 1 and 20 in mode 2.7 C4 Value must be between 1 and 15 in mode 1, and between 1

and 20 in mode 2.8 C5 Value must be between 1 and 15 in mode 1, and between 1



and 20 in mode 2.11 F1 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.12 F2 Setting must be either 'ltch'(ie. latched) or 'off' in both mode

1 and mode 2.13 F3 Setting must be either 'ltch'(ie. latched) or 'off' in both mode

1 and mode 2.14 F4 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.15 F5 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.16 ___ Operator interface was in use when power supply was lost.

Settings must be checked and the relay restored to service.

*See Sections 2.3 and 2.4 for a description of the various code and function settings.


CHAPTER 9

COMMISSIONING INSTRUCTIONS


Page 1 of 10

Section 1. GENERAL

The MJTW 01 is a voice frequency high-security both-ways direct intertrippingequipment which provides two independent protection signalling commands over asingle telecommunications link. It comprises a controller module and a modemhoused together in a 19 inch semi-projecting rack mounted case. The controllermodule is based on the MVTR 52 autoreclose relay with different input/outputcircuitry to suit intertripping applications. The modem is the same as is used in theHSDI-3.

The equipment is provided with five relay output elements labelled as trip 1, trip 2,test, communications failure, and scheme fault. The trip output elements each providefour normally open contact pairs, the test and communications failure output elementseach provide two normally open contact pairs, and the scheme fault element providesone normally closed contact which is held open when the equipment is functioningcorrectly in the scheme.

The relay has three opto-isolated digital inputs labelled trip 1, trip 2, and test. Twoversions of opto-isolated input are available to cover the range of battery voltages. Thelow voltage version covers the range 24 - 54V, and the high voltage version covers therange 110 - 125V.

Two versions of auxiliary power supply input circuitry are available to cover thestandard range of battery voltages. The low voltage version covers the range 24 - 54V,and the high voltage version covers the range 110 - 250V. Generally, the auxiliarypower supply voltage (Vx1) will differ from the opto-isolated input voltages (Vx2),but all three opto-isolated inputs will have the same rating. The input voltage rangesare given in the table below.

Version NominalVolts

MaximumVolts

MinimumVolts

Low Voltage 24/54 65 19

High Voltage(power supply)

110/250 300 87.5

High Voltage(opto-inputs)

110/125 150 87.5

Three versions of modem are available. There is one 1200 baud option and two 600baud options. Equipment fitted with a 1200 baud modem achieves faster operatingtimes than equipment fitted with a 600 baud modem due to the faster signalling speed.

Before commissioning the MJTW 01 it is necessary for the commissioning engineerto have full details of the settings to be used. Of particular importance are: therequired mode of operation, the channel monitor codes to be used, and the trip codesto be used.


Page 2 of 10

Section 2. COMMISSIONING PRELIMINARIES

2.1 Handling of electronic equipment

A person's normal movements can easily generate electrostatic potentials of severalthousand volts. Discharge of these voltages into semiconductor devices whenhandling electronics circuits can cause serious damage, which often may not beimmediately apparent but the reliability of the circuit will have been reduced.

The electronics circuits of AREVA T&D productsare completely safe from electrostatic discharge when housed in the case. Do not expose them to the risk of damage by withdrawing modules unnecessarily.

Each module incorporates the highest practicable protection for its semiconductordevices. However, if it becomes necessary to withdraw a module the followingprecautions should be taken to preserve the high reliability and long life for which theequipment has been designed and manufactured.

(1) Before removing a module, ensure that you are at the same electrostaticpotential as the equipment by touching the case.

(2) Handle the module by its handles, frame, or edges of printed circuit boards.Avoid touching the electronic components, printed circuit track, orconnectors.

(3) Do not pass the module to any person without first ensuring that you are bothat the same electrostatic potential. Shaking hands achieves equipotential.

(4) Place the module on an anti-static surface, or on a conductive surface whichis at the same potential as yourself.

(5) Store or transport the module in a conductive bag.

More information on safe working procedures for all electronic equipment can befound in BS5783 and IEC 147-0F.

If making measurements on the internal electronic circuitry of an equipment inservice, it is preferable to be earthed to the case with a conductive wrist strap. Thewrist strap should have a resistance to ground between 500kΩ to 10MΩ. If a wriststrap is not available, regular contact with the case should be maintained to preventthe build up of static. Instrumentation which may be used for making measurementsshould be earthed to the case whenever possible.



Page 3 of 10

2.2 Earthing

Ensure that the case earthing terminal above the rear terminal blocks is used toconnect the relay to the local earth bar.

2.3 Inspection

With no dc auxiliary voltage connected, carefully examine the relay to ensure that nodamage has occurred during transit. Check on the front nameplate that the modelnumber and rating information are correct.

Vx1 - Rated voltage of auxiliary supply to the controller module.

Vx2 - Rated voltage of auxiliary supply to the opto-isolated inputs used toinitiate tripping.

Unlock and open the hinged front nameplate. Check that the module references agreewith the details on the rating label and that the modules are connected together withthe 20-way IDC ribbon cable assembly.

2.4 Wiring

Check that the external wiring is correct to the relevant external connection diagramand/or scheme diagram. If a test block type MMLG is provided, the connectionsshould be checked to the scheme diagram, particularly that the supply connections areto the 'live' side of the test block (coloured orange and with allocated odd numberedterminals 1, 3, 5, 7 etc.). The auxiliary supply voltage Vx1 for the scheme should berouted via test block terminals 13 and 15.

The connections to telephone equipment are made at a DIN rail mounted terminalblock inside the relay case. The use of screened cable is recommended for connectionto the telephone circuits with the cable screen being connected to case earth inside thecase. Additionally it should be checked that the routing of the cable connections to thetelephone circuits is routed wherever possible away from the other externalconnections to the relay.

2.5 Insulation tests

The insulation of the relay and its wiring may be tested between

– all electrically isolated circuits– all circuits and earth.

An electronic or brushless insulation tester having a voltage not exceeding 1000V dcshould be used. Accessible terminals of the same circuit should first be strappedtogether. Deliberate circuit earthing links removed for the tests must be subsequentlyreplaced.

The outgoing terminal allocation for the relay is shown on the external connectiondiagram.


Page 4 of 10

2.6 Isolate contacts

Isolate the output trip contacts of the relay from operating the tripping circuits.


Page 5 of 10

Section 3. COMMISSIONING TESTS

The following test instructions are based on injecting signals directly into the relayterminals. However if an MMLG test block is incorporated in the scheme, then it ismore convenient to inject signals into the MMLG test block. Refer to the relevantscheme diagram for details.

3.1 Test equipment

Frequency counter/timer, min 5 decades, 0-100kHz ± 1Hz, time 10µs - 1s ±10µs.Digital timer (GECA P&C)Power meter (dB measuring)Digital oscilloscopeMultimeterTest leads fitted with 2mm plugs

3.2 Power-up

Disconnect the connections to the telephone circuit by opening the test links on theDIN rail mounted terminal block.

3.2.1 DC auxiliary supply

Check the rated auxiliary supply voltage Vx1 on the relay front nameplate label andconnect a suitably rated smoothed dc supply or station battery supply to relay MIDOSterminals 41 (+) and 42 (-). Before switching on the supply to the relay check that the'Scheme Fault' relay contact (MIDOS terminals 26-28) is closed.

Switch on the supply and check the following:

The 'Scheme Fault' and 'Communications Failure' leds on the front of the controllermodule are illuminated.

There is no display on the liquid crystal display.

The 'communications failure' relay contacts and the 'scheme fault' relay contacts areclosed.

3.2.2 Mode setting

Set the relay operating mode (either 1 or 2) according to customers requirements.

With the exception of the channel monitor codes and the trip codes, change all othersettings according to the users requirements. Note that the number of settings variesaccording to the relays operating mode. The default settings are given in the tablesbelow :


Page 6 of 10

Operation in Mode 1

Key Index Code Setting

Mode of operation C1 1

Transmit channel ID code C2 7t

Receive channel ID code C3 7t

Transmit trip 1 code C4 15

Receive trip 1 code C5 15



Minimum trip contact closure time F1 0.2s

Action of trip 1 outputs on comm fail F2 latch

Action of trip 2 outputs on comm fail F3 latch

Minimum comm fail output closuretime

F4 0.2s

Comm fail output reset time F5 0.2s

Operation in Mode 2


Mode of operation C1 2

Transmit monitor code C2 4

Receive monitor code C3 4





Minimum trip contact closure time F1 0.2s

Action of trip 1 outputs on comm fail F2 off

Action of trip 2 outputs on comm fail F3 off


Page 7 of 10


Minimum comm fail output closuretime

F4 0.2s

Comm fail output reset time F5 0.2s

3.2.3 Software reference

Record the software reference number and restore the relay to service.

3.3 Commission Modem

Commission the modem according to the instructions in Publication R-5927, Section8 in conjunction with the following notes:

3.3.1 Transmit level to line

It is important that the output level for equipment using BT private rented circuitsshould not exceed -13dBm. When more than one signalling system is present on thepilot circuit, the signalling levels of each tone must not exceed the levels given belowif the maximum permitted signalling level is not to be exceeded. Adjust the attenuatorswitch pads to give correct level to line.

1 tone - maximum level - 13dBm2 tones - maximum level -16dBm

It should also be noted that in mode 2, trip signals are transmitted at a level 3dBhigher than the monitor signal level and this must also be taken into account. Therecommended level to line for a monitor signal in mode 2 is therefore :

-17dBm ±0.5dB for a single equipment-20dBm ±0.5dB for two equipment sharing the pilot.

If it is not possible to make a direct reading on line, a level 3dB higher than the abovemay be set on modem test points, assuming 3dB loss through the isolationtransformers.

3.3.2 Characteristic frequency

With the modem set in test BIAS mode (SW1) and NORMAL output (SW2), measurethe output frequency. This should be

1500 ± 1Hz for 600 baud channel 1.2500 ± 1Hz for 600 baud channel 2.1700 ± 1Hz for 1200 baud.

Note this frequency is an average frequency and the frequency counter used shouldhave a gate period of at least 1 second.

Leave in this mode for initial setting of remote receiver.


Page 8 of 10

3.3.3 Receive VF levels

Measure the incoming VF level to the receiver on the modem front panel test points(REC). With the remote transmitter set as above, the level should be in the range -16dBm to -30dBm.

3.3.4 Receiver setting

Depress the SET RECEIVE LEVEL push-button and adjust the associatedpotentiometer until the light emitting diode DCD is extinguished (anticlockwise).Turn the potentiometer clockwise until DCD just re-illuminates and release push-button.

3.3.5 Bias distortion

Adjust the BIAS potentiometer until the signal at the RD test point is a square waveoutput with a 50:50 MARK:SPACE ratio with bit width 1.67ms at 600 baud or0.833ms at 1200 baud.

Note that the connections to the telephone circuit may require remaking at the testlinks on the DIN rail mounted terminal block to allow the modem to be set up. Whenthe modem is commissioned, the test links should be re-opened.

3.4 Communication loopback

Set SW1 on the front of the modem to NORMAL and set SW2 to LOOPBACK.

The 'Scheme Fault' and 'Communications Failure' leds on the front of the controllermodule should extinguish. Check that the 'Scheme Fault' and 'CommunicationsFailure' output contacts open.

3.5 Commissioning for mode 1 operation

The following Section applies only to equipment which has been configured for mode1 operation. For equipment which has been configured for mode 2 operation, proceedfrom Section 3.6.

3.5.1 Operation of test function in mode 1

Check the rated auxiliary supply voltage Vx2 on the relay front nameplate label andapply a suitably rated smoothed dc supply or station battery supply to the test input(MIDOS terminals 19(+) and 17(-)). Check that the test led. on the front of the moduleilluminates, and that all of the test output contacts close. Remove the signal.

Change the 'Transmit channel ID code' to '1', enter the value and restore to service.Check that the 'Communications Failure' led. and the 'Scheme Fault' led. bothilluminate, and that the 'Scheme Fault' contacts and both of the 'CommunicationsFailure' contacts close.

Change the 'receive channel ID code' to '1', enter the value and restore to service. The'Communications Failure' and 'Scheme Fault' indications should clear. Reapply the


Page 9 of 10

voltage signal to the test input. The test led. should remain extinguished, and all thetest output contacts should remain open.

Remove the signal.

3.5.2 Mode 1 trip operation

Apply a suitably rated smoothed dc supply or station battery supply simultaneously tothe trip 1 input (MIDOS terminals 27(+) and 25(-)) and the trip 2 input (MIDOSterminals 23(+) and 21(-)). Monitor all trip 1 output contacts and all trip 2 outputcontacts and measure the operate time for both trip 1 and trip 2 from inputenergisation to output contact closure. Check that the operate time is less than 100msfor 600 baud operation, or 55ms for 1200 baud operation. Check that the four ledslabelled 'trip 1 send', 'trip 2 send', 'trip 1 receive', and 'trip 2 receive' are illuminated.Remove the energising signal.

3.5.3 Receive trip 1 codes

Change the 'Receive trip 1 code' to '1', enter the value and restore to service. Repeat3.5.2 but this time the trip 1 output contacts and the ' trip 1 receive' led. should notrespond.


Change the 'receive trip 2 code' to '2', enter the value and restore to service. Repeat3.5.2 but this time the trip 1 output contacts, the 'trip 1 Receive' led., the trip 2 outputcontacts and the 'trip 2 Receive' led. should not respond.

3.5.5 Communications failure time

Switch SW1 on the front of the modem to test MK and check that the relay indicates acommunications failure after approximately 1 second. Set SW1 back to NORMAL.

3.5.6 Transmit trip codes

Change the 'transmit trip 1 code' to '1' and the 'transmit trip 2 code' to '2', enter thevalues and restore to service. Repeat 3.5.2. Check that both trips are received. Leavethe voltage signal to the trip inputs applied.

3.5.7 Trip output contact action on communications failure

Set SW2 on the front of the modem to NORMAL. Check that the relay indicates acommunications failure after approximately 1 second. Check that the trip outputcontacts remain closed and the 'trip 1 receive' and 'trip 2 receive' leds remainilluminated if the outputs are set to 'latch' in the event of a communications failure, or,that the trip output contacts open and the 'trip 1 receive' and 'trip 2 receive' leds areextinguished if the outputs are set to go off in the event of a communications failure.

Re-make the communications link and remove the energising quantity to the tripinputs.

Proceed to Section 3.7.


Page 10 of 10


The following section applies only to equipment which has been configured formode 2 operation. For equipment which has been configured for mode 1 operation,Section 3.5 applies.

3.6.1 Mode 2 trip 1 operation

Check the rated auxiliary supply voltage Vx2 on the relay front nameplate label andapply a suitably rated smoothed dc supply or station battery supply to the trip 1 input(MIDOS terminals 27(+) and 25(-)). Monitor all trip 1 output contacts and measurethe operate time for trip 1 from input energisation to output contact closure. Checkthat the operate time is less than 45ms for 600 baud operation, or 25ms for 1200 baudoperation. Record the time. Check that the leds labelled 'trip 1 send' and 'trip 1 receive'are illuminated.

Switch SW2 to NORMAL and check that the modem send signal level is boosted by3dB over its nominal value. Return SW2 to LOOPBACK and remove the trip 1 inputenergising signal.


Apply a suitably rated smoothed dc supply or station battery supply to the trip 2 input(MIDOS terminals 23(+) and 21(-)). Monitor all trip 2 output contacts and measurethe operate time for trip 2 from input energisation to output contact closure. Checkthat the operate time is less than 45ms for 600 baud operation, or 25ms for 1200 baudoperation. Record the time. Check that the leds labelled 'trip 2 send', and 'trip 2receive' are illuminated.

Switch SW2 to NORMAL and check that the modem send signal level is boosted by3dB over its nominal value. Return SW2 to LOOPBACK and remove the trip 2 inputenergising signal.

3.6.3 Mode 2 both trips operation

Apply a suitably rated smoothed dc supply or station battery supply simultaneously tothe trip 1 input (MIDOS terminals 27(+) and 25(-)) and the trip 2 input (MIDOSterminals 23(+) and 21(-)). Monitor all trip 1 output contacts and all trip 2 outputcontacts and measure the operate time for both trip 1 and trip 2 from inputenergisation to output contact closure. Check that the one of the trip operate times isless than 45ms for 600 baud operation, or less than 25ms for 1200 baud operation, andthat the other trip time is less than 70ms for 600 baud operation, or less than 40ms for1200 baud operation. Record the times. Check that the four leds labelled 'trip 1 send','trip 2 send', 'trip 1 receive', and 'trip 2 receive' are illuminated.

Switch SW2 to NORMAL and check that the modem send signal level is boosted by3dB over its nominal value. Return SW2 to LOOPBACK and remove the trip inputenergising signals.


Page 11 of 10


Change the 'receive trip 1 code' to '5', enter the value and restore to service. Repeat3.6.1 but this time the trip 1 output contacts and the ' trip 1 receive' led. should notrespond.


Change the 'receive trip 2 code' to '15', enter the value and restore to service. Repeat3.6.2 but this time the trip 1 output contacts, the 'trip 1 receive' led., the trip 2 outputcontacts and the 'trip 2 receive' led. should not respond.


Set SW1 on the front of the modem to test MK and check that the relay indicates acommunications failure after approximately one second. Set SW1 back to NORMAL.


Change the 'Transmit trip 1 code' to '5' and the 'Transmit trip 2 code' to '15', enter thevalues and restore to service. Repeat 3.6.3. Check that both trips are received. Leavethe voltage signal to the trip inputs applied.


Set SW2 on the front of the modem to NORMAL. Check that the relay indicates acommunications failure after approximately 1 second. Check that the trip outputcontacts remain closed, and the 'trip 1 receive' and 'trip 2 receive' leds remainilluminated if the outputs are set to 'latch' in the event of a communications failure, or,that the trip output contacts open, and the 'trip 1 Receive' and 'trip 2 Receive' leds areextinguished if the outputs are set to go off in the event of a communications failure.

Re-make the communications link and remove the energising quantity to the tripinputs.

3.6.9 Mode 2 test mode

Set the 'receive monitor code' to '6', enter the value and restore to service. Check that acommunications failure is indicated.

Depress the 'test' key on the controller module keypad and release. Check that the testled. illuminates and that the communications failure indication is cleared.

Depress the 'test' key again and release. Check that the test led. is extinguished andthat the communications failure indication is restored.

3.7 User code settings

Set the transmit channel ID/transmit monitor, the receive channel ID/receive monitor,and all the trip codes to the required user settings. Do this for both MJTW 01 units inthe scheme.


Page 12 of 10

3.8 End-to-end tests

For the end-to-end tests to be performed it is necessary either to have acommissioning engineer present at both ends of the scheme, or to use the trip outputsat the remote end to initiate a return of the trip command from the remote end usingthe return intertrip commands. The operation times of the 'looped back' trip times maybe recorded if the latter configuration is used.

3.8.1 Monitor restoration

Ensure that the connections to the telephone circuit are made by closing the test linkson the DIN rail mounted terminal block at both ends of the scheme.

Set SW1 and SW2 on the modems at both ends of the scheme to NORMAL and checkthat the communications failure and scheme fault indications are cleared at both endsof the scheme.

3.8.2 Trip 1 end-to-end

Energise the trip 1 input and check that the corresponding trip 1 output contacts close.If the trip command loopback configuration is used, the overall operation time shouldbe twice the one-way operation time measured in Section 3.5 or 3.6.


Energise the trip 2 input and check that the corresponding trip 2 output contacts close.If the trip command loopback configuration is used, the overall operation time shouldbe twice the one-way operation time measured in Section 3.5 or 3.6.


CHAPTER 10

FAULT FINDING INSTRUCTIONS


Page 1 of 6


The equipment must be handled with care. See Chapter 3 for instructions oninstallation and handling of the relay. Always ensure the power supply has beenturned off before either module is withdrawn from the case.

A failure in the power supply or the printed circuit boards is likely to requirespecialist equipment for detailed analysis, and the relay should be returned to thefactory in this event. The following is a description of some fault finding analysiswhich can be carried out to resolve directly, some of the problems which may arise.

Section 2. NOTHING HAPPENS WHEN THE POWER IS SWITCHEDON

This is signalled when there is no led indication on the modem or the controllermodule.

2.1. DC voltage supply

Cross reference the module number on the controller module to see if the module is ahigh or low voltage module, with the numbers given in Section 2 of Chapter 1. SeeSection 4.2 Chapter 2 for the correct voltage range for both the power supply, andthe trip and test inputs. Check that the correct voltage supply has been wired with thecorrect polarity to the correct terminals as given in the external connection diagram,Addendum.

The power supply fuse may need to be replaced if the power supply previouslyconnected was too high for the module. This is found by first of all withdrawing thecontroller module from the case having taking precautions against electrostaticdischarge as outlined in Chapter 3. The fuse can be found on printed circuit boardZH0811 of the module which is attached to the inside of the plastic MIDOSconnector. It is the only user serviceable part of the relay. To replace, remove theplastic connector from the sides of the module, taking utmost care not to separate anyof the connected wires, and take out the fuse. Replace the fuse with a similar type.For a high voltage power supply use a 1.25A/250Vdc fuse, or for a low voltagepower supply use a 1A/250Vdc fuse. Both are fast acting, low breaking capacityfuses. They can be ordered from AREVA T&D by quoting bin number ZB9029 091 for the 1.25A, or ZB9029 090 for the 1A fuse, or from manufacturers such as Belling Lee quoting L1427B, or Bulgin quoting F370 and specifying which fuse is required. Repeated failure of the fuse is however, indication of a more serious problem and the relay should be returned to the factory for repair if this happens.


Page 2 of 6

Section 3. ERROR MESSAGES

If an error message of the form 'err x', where 'x' is a number, is displayed on thelcd, check the error list below and take the recommended action to correct the error ifappropriate.

Error checking is carried out when there is a power up or a reset condition. In theunlikely event of an error message occurring on the lcd, check the error list to seewhat the problem is and take appropriate action to solve the problem. Oninitialisation, the relay checks for the presence of a modem by monitoring a transmitclock input. If a valid input is not received from the modem, an error is reported.

Rectifying errors 1 and 2 involve connecting the correct modem, either 600 or 1200baud, to the drawout controller module, having removed the auxiliary power supply.The modem is supplied as part of the equipment and is already connected, so thereshould not be any problem, unless one of the modules is removed. If ensuring correctconnection of a suitable modem via the 20-way IDC cable does not resolve the errorthe relay will need to be returned to the factory.

Errors 3 to 15 indicate an out of range value in a setting field. If the operator choosesto view the erroneous setting, the setting field will be displayed as blank to indicatethe error. This can be corrected by using the operator interface to change the settingto one of the available values, as explained in Section 2.3 of Chapter 8. Finally, error16 indicates that the operator interface was in use when the equipment lost its powersupply. Ensure that the settings are as they should be by pressing the 'code setting'key and each of the numbers from 1 to 7, and then the 'function setting' key and theeach of the numbers 1 to 5. Press the restore key to return the equipment back toservice.


Page 3 of 6

3.1 Error list

Indexnumber

Setting* Problem

1 ___ Modem is not connected2 ___ Incorrect modem baud rate3 C1 Out of range - value must be 1 or 24 C1 Out of range - value must be 1 or 25 C2 Value must be between 1 and 15 or 1t and 7t in mode 1, and

between 1 and 20 in mode 2.6 C3 Value must be between 1 and 15 or 1t and 7t in mode 1, and

between 1 and 20 in mode 2.7 C4 Value must be between 1 and 15 in mode 1, and between 1




and 20 in mode 2.11 F1 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.12 F2 Setting must be either 'ltch'(ie. latched) or 'off' in both mode

1 and mode 2.13 F3 Setting must be either 'ltch'(ie. latched) or 'off' in both mode

1 and mode 2.14 F4 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.15 F5 Value must be between 0.1 and 0.4 seconds in both mode 1

and mode 2.16 ___ Operator interface was in use when power supply was lost.

Settings must be checked and the relay restored to service.

* See Sections 4.1 and 4.4 of Chapter 2 for a description of the various code andfunction settings.


Page 4 of 6

Section 4. COMMUNICATIONS FAILURE ALARM

The scheme fault alarm and led should operate every time the communicationsfailure alarm and led operate. Communications failure may be due tocommunications link failure, modem failure or incompatibility, or invalid codesettings.

4.1. Modem

Modem failure or modem non-connection to the controller module is indicated by noilluminated leds on the modem front or an error message on the lcd, see Section 3 ofthis Chapter. A detailed description of the modem is given in Chapter 5 but thefollowing precautions may be taken to ensure correct operation of the modem.

Check that the modem ribbon cable is plugged into the control module at one end,and into the modem at the other end. Check that the cable connections from the D-connectors on the back of the modem to the DIN rail mounted terminal block arewired according to the external connection diagram given in Chapter 11.

Ensure switch 1 on the modem front is set to the normal position and switch 2 is setto the normal position for normal intertripping relay action.

Check the module number on the modem to see if the modem has a Baud rate of 600or 1200. If it is a 600 Baud, check if the equipment is operating on channel 1 or 2.See Chapter 2 Section 4.1. Ensure that the modems at either end of thecommunications link have the same Baud rate and channel setting.

4.2. Communications Link

Indications of a communications link problem are firstly, a modem receive data (RD)led which does not flicker - this shows that the modem is not receiving any data fromthe communications link. Secondly, if the carrier alarm (CA) led is illuminated or thedata carrier detect (DCD) led is extinguished, the received signal power level of themodem may be too high or too low in which case the relay should be re-commissioned. Check the receive power level with a suitable power meter accordingto the values given in Section 3.1 of Chapter 5 on the modem and adjust the level ifnecessary. If there is no received signal, check the voice frequency connections toboth relays in the scheme, using the external connection diagram, Chapter 11.

If there is still no received signal, loopbacks can be placed on the communicationslink at various points, working back along the communications link from the relay inthe following manner until the break is found. In mode 2 the test facility makes thetransmit monitor code temporarily the same as the receive monitor code. The relaycan then be switched into loopback via a switch on the modem front. If thecommunications failure indications have gone away, the modem can be switchedback to the normal position and a test link can be placed between the receive andtransmit terminals on the DIN rail of the voice frequency terminal block above the


Page 5 of 6

modem. If the communications failure indications have now gone away, the test linkcan be placed further back along the communications' link until the source of thecommunications failure may be found. When the communications link is re-established, the modem receive level will need to be re-checked as given in Chapter5, Section 3.1.

4.3. Code Settings

Check that the transmit codes C2, C4, and C6 (see Section 3.1 Chapter 2) have eachbeen set to the same code as the receive codes on the other end C3, C5, C7respectively. This can be done using the operator interface, see operatinginstructions, Chapter 8.

If the equipment is operating in mode 2, there needs to be reception of monitor codefor a time before a trip message will be accepted without indication of acommunications failure. If this is the case, de-energise the trip input until thecommunications failure indications have gone away and then the input can be re-energised if required.

Section 5. SCHEME FAULT ALARM

If the scheme fault alarm operates without the communications failure alarm uponpower-up, the operator interface may have been invoked when power supply to theequipment was lost. In this case the scheme fault led on the relay will illuminate. Ifthe power supply is lost entirely, however, the scheme fault output contact willoperate but the led will not illuminate.

Section 6. COMMAND TRANSFER FAILURE

In the case of healthy communications, and a verified wiring scheme, if a trip or atest input energised with a voltage within the correct voltage range for the module,does not cause a trip or a test output contact to operate as expected, there may be aproblem with the input or output circuitry of the respective relays or there may be aninvalid code setting on one of the relays. Switch the modem into the loopbackposition and make the transmit codes the same as the receive codes, to check thelocal end relay for input energisation and output contact closure.


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6.1. Test

6.1.1 Mode 1:

Note: test input energisation has an effect only on equipment configured formode 1 operation.

In the case of healthy communications, and with the modem in loopback, if a testinput energised with a voltage within the correct voltage range for the module, doesnot cause the test output contact to operate, check that the module has beenprogrammed with a test code on both the transmit channel ID. and the receivechannel ID.

If the test receive led is not illuminated in either of the above conditions, check thedisplay on the lcd of the current status of the test input. This is done by pressing the'step' key when the relay is on-line, thus bringing it off-line and displaying the statusof the test input with three presses of the 'step' key. If this indicates that there is testinput energisation, the test led may be faulty and the relay will need to be returned tothe factory for repair. If the lcd indicates a non-energised input, the input circuitry isfaulty and the relay must be returned for repair. If the led and lcd indications are asexpected but the output contacts do not close, the output element is faulty and therelay must again be returned.

6.1.2 Mode 2:

If pressing the test key fails to operate the led and the test output contact on the localend equipment, the equipment is faulty and must be returned to the factory.

If the test receive led is not illuminated in either of the above conditions, check thedisplay on the lcd of the current status of the test input. This is done by pressing the'step' key when the relay is on-line, thus bringing it off-line and displaying the statusof the test input with three presses of the 'step' key. If this indicates that there is testinput energisation, the test led may be faulty and the relay will need to be returned tothe factory for repair. If the lcd indicates a non-energised input, the input circuitry isfaulty and the relay must be returned for repair. If the led and lcd indications are asexpected but the output contacts do not close, the output element is faulty and therelay must again be returned.

6.2. Trip

Check the trip send led to see if the input energisation has registered with the relay. Ifthe send led is not illuminated, check the display on the lcd of the current status ofthe trip inputs. This is done by pressing the 'step' key when the relay is on-line, thusbringing it off-line and displaying the status of trip 1 with the first press of the 'step'key, trip 2 with the second, and test with the third. If this indicates that there is tripenergisation, the led may be faulty and the relay will need to be returned to thefactory for repair. If the lcd indicates a non-energised input, the input circuitry isfaulty and the relay must be returned for repair.


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There may be an invalid trip code programmed into the relay. With the loopbackswitch on the modem set to normal, check that the transmit codes C2, C4, and C6(see Section 3.1 Chapter 2) have each been set to the same code as the receive codeson the other end C3, C5, C7 respectively. This can be done using the operatorinterface, see operating instructions, Chapter 8. If the codes match, and either the tripreceived led indications fail, or the output contacts do not close, the module is faultyand the relay must be returned to the factory for repair.


ADDENDUM

MJTW01 R8124SERVICE MANUAL COMMISSIONING TEST RECORD

Page 1 of 5

STATION DATE

CIRCUIT

RELAY SERIALNO.

RELAYMODELNO.

DC AUXILIARY VOLTAGE Vx1

Vx2

3.2.1 Check polarity of dc auxiliary voltage Vx1 terminal 41(+)

42(–)

Check dc auxiliary voltage Vx1 V

Check 'scheme fault' relay contacts before switch on (closed)

Switch on dc auxiliary supply and check:

Scheme fault led and comms failure led illuminated

No display on lcd

Scheme fault and comms failure contacts closed

3.3.1 Transmit level to line measurement

Mode 1 1 tone max –13dBm

2 tones max –16dBm

Mode 2 1 tone max –17dBm

2 tones max –20dBm

3.3.2 Check frequency

1500Hz ±1Hz for 600 baud channel 1 Hz

2500Hz ±1Hz for 600 baud channel 2 Hz

1700Hz ±1Hz for 1200 baud Hz

3.3.3 Receiver VF levels

Modem test point REC –16dBm to –30dBm dBm

3.3.4 Receiver setting

3.3.5 Bias distortion


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Monitoring RD test point 50:50 mark:space

1.67ms at 600 baud ms

0.833ms at 1200 baud ms

3.4 Communications loopback

Check 'scheme fault' leds lit and contacts open

Check 'comms failure' leds lit and contacts open



17(–)

Check dc auxiliary voltage Vx2

Check test led illuminates

Check test output contacts close

Remove test signal

Change 'Transmit channel ID code' to '1', enter and restore toservice

Check 'scheme fault leds lit and contacts closed

Check 'comms failure' leds lit and contacts closed

Change 'Receive channel ID code' to '1', enter and restore toservice

Check 'scheme fault' leds unlit and contacts open

Check 'comms failure' leds unlit and contacts open

Reapply test signal

Test led remains unlit

Test output contact remains open

3.5.2 Mode 1 trip operation

Monitor all trip 1 and trip 2 output contacts for operation

trip 1 ms ms ms ms

trip 2 ms ms ms ms

Check leds are illuminated

trip 1 send


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trip 2 send

trip 1 receive

trip 2 receive


Check no response from trip 1 contacts

Check no response from trip 1 receive led





SW1 to test Mk - communications failure after 1 second


Check both trips received


Check comms failure led lights after 1 second

Check either trip output contacts remain closed

and trip 1 receive and trip 2 receive leds are lit

or trip output contacts are open

and trip 1 receive and trip 2 receive leds extinguish if outputsare set to go off


Check that the 'scheme fault' and 'comms failure' indicationsare clear at both ends of the scheme


Check remote end trips with trip 1 energised

Operate time at local end with remote trip 1 loopbacked ms


Check remote end trips with trip 2 energised

Operate time at local end with remote trip 2 loopbacked ms


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25(–)

Check dc auxiliary voltage Vx2

trip 1 operate ms ms ms ms

Check 'trip 1 send' and 'trip 1 receive' leds lit

Check send signal level boosted when SW2 to NORMAL dBm


Check polarity of dc auxiliary voltage Vx2 terminal 23(+)

21(–)

trip 2 operate ms ms ms ms

Check 'trip 2 send' and 'trip 2 receive' leds lit

Check send signal level boosted when SW2 to NORMAL dBm

3.6.3 Mode 2 both trips operation

One trip operates ms ms

The other trip operates ms ms








SW1 to test Mk - communications failure after 1 second


Check both trips received


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Check comms failure led lights after 1 second

Check either trip output contacts remain closed

and trip 1 receive and trip 2 receive leds are lit

or trip output contacts are open

and trip 1 receive and trip 2 receive leds extinguish if outputsare set to go off

3.6.9 Mode 2 test mode

Check communications failure indication

Check test led lights

Communications failure clears

Check test led clears

Communications failure led lights


Check that 'scheme fault' and 'comms failure' indications areclear at both ends of the scheme


Check remote end trips with trip 1 input energised

Measure operate time at local end with remote trip 1loopbacked

ms


Check remote end trips with trip 2 input energised

Measure operate time at local end with remot trip 2loopbacked

ms

------------------------------------------------------------------------------------- Commissioning Engineer Customer Witness

-------------------------------------------------------------------------------------Company Company

-------------------------------------------------------------------------------------- Date Date

AREVA T&D's Automation & Information Systems Business www.areva-td.com T&D Worldwide Contact Centre online 24 hours a day: +44 (0) 1785 25 00 70 http://www.areva-td.com/contactcentre/

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R8124B MJTW01

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