Example_Overcurrent_OvercurrentNonDirectional_ENU.pdf

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Testing Non-DirectionalOvercurrent Protection

Practical Example ofUse
mailto:[email protected]:[email protected]


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2

Testing Non-Directional Overcurrent Protection

Manual Version: Expl_OVC_NonDir.AE.1 - Year 2011

OMICRON electronics. All rights reserved.

This manual is a publication of OMICRON electronics GmbH.

All rights including translation reserved.

The product information, specifications, and technical data embodied in this manual represent the technical

status at the time of writing and are subject to change without prior notice.

We have done our best to ensure that the information given in this manual is useful, accurate, up-to-date and

reliable. However, OMICRON electronics does not assume responsibility for any inaccuracies which may be

present.

The user is responsible for every application that makes use of an OMICRON product.

OMICRON electronics translates this manual from the source language English into a number of other

languages. Any translation of this manual is done for local requirements, and in the event of a dispute between

the English and a non-English version, the English version of this manual shall govern.


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OMICRON 2011 Page 3 of 20

Preface

This paper describes how to test non-directional overcurrent protection elements. It contains an applicationexample which will be used throughout the paper. The theoretical background of the non-directionalovercurrent protection will be explained. This paper also covers the definition of the necessary Test Object

settings as well as the Hardware Configurationfor non-directional overcurrent tests. Finally theOvercurrenttest module is used to perform the tests which are needed for the non-directional overcurrentprotection function.

Supplements: Sample Control CenterfileExample_Overcurrent_OvercurrentNonDirectional_ENU.occ (referred to in thisdocument).

Requirements: Test Universe2.40 or later; Overcurrentand Control Centerlicenses.

1 Application Example

10.5 kV

200/1

Overcurrent Relay

2nd

element (50/51) / non-directional characteristic (DTOC)

1stelement (51) / non-directional characteristic (IDMT)

Protection functions

Figure 1: Feeder connection diagram of the application example

Parameter Name Parameter Value Notes

Frequency 50 Hz

CT (primary/secondary) 200 A /1 A

1st

element

IEC Very Inverse Tripping characteristic

300 A Pick-up 1.5 x In CT primary

1.2Time multiplier setting (TD; TMS; P, etc.) (onlyfor IDMT characteristics)

2nd

element

DTOC Tripping characteristic

600 A Pick-up 3 x In CT primary

100 ms Trip time delay

Table 1: Relay parameters for this example


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2 Theoretical Introduction to Overcurrent Characteristics

2.1 Tripping Characteristics

There are two major overcurrent characteristic types: Inverse time and definite time.

Tripping Characteristics

Definite Time Overcurrent Relay Inverse-Definite Minimum Time

Overcurrent Relay

Trip-time charateristic of a two-

element DTOC relay

t/s

t(1stel.)

t(2ndel.)

1stelement 2ndelement I/IP

50-1/51 or 50N-1/51N 50-2 or 50N-2

Trip-time characteristic of an

IDMT overcurrent relay

51 or 51N or 67

t/s

I/IP1stelement 2ndelement

t(2ndel.)

Inverse time characteristics can have different basic shapes such as these:

Characteristic Formula Annotation

LTI (long time inverse) PP 1

t TI I

Suitable for motors, for example.

SI (standard inverse)

P0.02

P

0.14

1t T

I I

VI (very inverse) PP

.

1t T

I I

EI (extremely inverse)

P2

P

80

1t T

I I

Suitable for co-ordination with fusetripping characteristics.

Table 2: IDMT tripping characteristics (see IEC 60255-3 or BS 142, section 3.5.2)

t = trip time in secondsTPor TMS = setting value of the time multiplierI = fault currentIP = setting value of the pick-up current

Note: Some relays have an increased pick-up value for IDMT characteristics. For example, the relayused in this example has an actual pick-up value that is 1.1 times higher than the IPsetting.


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2.2 IDMT Characteristics (51, 51N)

As the properties of the operational equipment differ considerably (overload, short circuit behavior, etc.), thecharacteristics have to be adapted to this.

Figure 2: Parameters of an overcurrent relay (AREVA)

1. Tripping characteristic for the 1stelement (for this example IDMT IEC very inverse)

2. Directional function (for this example non-directional)

3. Pick-up setting (primary) of 1stelement

4. Pick-up value at 1.1 x IP

5. Time multiplier setting (TMS) for the 1stelement

6. Tripping characteristic for the 2nd

element (DTOC for this example)

7. Pick-up setting (primary) of 2nd

element

8. Trip time delay of 2nd

element

Figure 3: Comparison of IEC very inverse tripping characteristics with different time multiplier settings (TMS)

0.01

0.1

1

10

100

1000

200 300 400 500 600 700 800 900

IEC Very Inverse (TMS = 1.2) IEC Very Inverse (TMS = 4) IEC Very Inverse (TMS = 6)

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7867

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11

15

13

18

17

14

6


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3 Practical Introduction to Overcurrent Characteristic Testing

The Overcurrenttest module is designed for testing directional and non-directional overcurrent protectionfunctions with DTOC or IDMT tripping characteristics (short-circuit, thermal overload, zero sequence,negative sequence, and customized curve characteristics).

The test module can be found on the Start Pageof the OMICRON Test Universe. It can also be inserted intoan OCC File (Control Centerdocument).

3.1 Defining the Test Object

Before testing can begin the settings of the relay to be tested must be defined. In order to do that, theTest Objecthas to be opened by double clicking the Test Objectin the OCC file or by clicking theTest Objectbutton in the test module.


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3.1.1 Device Settings

General relay settings (e.g., relay type, relay ID, substation details, CT and VT parameters) are entered inthe RIOfunction Device.

Note: The parameters V maxand I maxlimit the output of the currents and voltages to preventdamage to the device under test. These values must be adapted to the respectiveHardware Configurationwhen connecting the outputs in parallel or when using an amplifier.The user should consult the manual of the device under test to make sure that its input ratingwill not be exceeded.


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3.1.2 Defining the Overcurrent Protection Parameters

More specific data concerning the overcurrent relay can be entered in the RIOfunction Overcurrent. Thedefinition of the overcurrent characteristic must also be made here.

Note: Once an Overcurrenttest module is inserted this RIOfunction is available.

Relay Parameters

This first tab contains the definition of the directional behavior as well as the relay tolerances.

1. Since we want to test a non-directional overcurrent relay this option has to be chosen.

2. The current and time tolerances can be obtained from the relay manual.

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Elements

This tab defines the characteristic of the different overcurrent elements.

The default overcurrent characteristic is shown above. It contains an IEC Definite Time scheme with oneelement for a phase overcurrent protection. This characteristic has to be adjusted to the parameters of therelay (Table 1):

1. In order to define the elements of the phase overcurrent protection, select Phaseas theSelected element type.Note:If other element types are also present in the relay select the related element types consecutivelyin (1)to enter these elements. The selection field shows the number of already defined related elementsand how many of these are marked as active.

2. This table shows the elements which define the tripping characteristic for the selected element type. Thename of the first element may be changed according to the name used in the relay, e.g., "I>1".

3. Change the characteristic type of the first element to IEC Very inverse(Table 1).

4. Afterwards set I Pick-upand the Time index.

5. As mentioned in chapter2.1 ,the 1stelement has an increased pick-up value (by factor 1.1). This has tobe considered in the Range limitsof the test object. In order to do that, select Activeand enter theincreased pick-up value in I min.

6. Now the second element can be added. It has an IEC Definite Timecharacteristic which might berenamed to "I>2". Also set I Pick-upand the Trip time.

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The list of the elements appearing after these adjustments is shown below.

1. The Reset Ratiomust also be checked in the manual.

The resulting overcurrent characteristic is shown below.

A 1stelement

B 2nd

element

11

1B

1A

A

B

A

B


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3.2 Global Hardware Configuration of the CMC Test Set

The global Hardware Configurationspecifies the general input/output configuration of the CMC test set. Itis valid for all subsequent test modules and, therefore, it has to be defined according to the relaysconnections. It can be opened by double clicking the Hardware Configurationentry in the OCC file.

3.2.1 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 1 A

IA

IB

IC

IN


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3.2.2 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 5 A

IB IN

IA IC

Note: Make sure that the rating of the wires is sufficient when connecting the outputs in parallel.

The following explanations only apply to protection relays with a secondary nominal current of1 A.


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3.2.3 Analog Outputs

The analog outputs, binary inputs and outputs can all be activated individually in the local HardwareConfigurationof the specific test module (see chapter3.3 ).

3.2.4 Binary Inputs

1. The start command is optional (it is needed if Startingis selected as the time reference in the testmodule or if a pick-up / drop-off test is required).

2. The trip command has to be connected to a binary input. BI1 BI10 can be used.

3. For wet contacts adapt the nominal voltages of the binary inputs to the voltage of the circuit breaker tripcommand or select Potential Freefor dry contacts.

4. The binary outputs and analog inputs etc. will not be used for the following tests.

Start

Trip

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3.2.5 Wiring of the Test Set for Relays with a Secondary Nominal Current of 1A

Note: The following wiring diagrams are examples only. The wiring of the analog current inputs maybe different if additional protective functions such as sensitive ground fault protection areprovided. In this case INmay be wired separately.

IN

IA

IB

IC

Protection

Relay

Trip

(+)

(-)

Start

(+)

(-)

optional

IN

IA

IB

IC

Protection

Relay

Trip

(+)

(-)

Start

(+)

(-)

optional


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3.3 Local Hardware Configuration for Non-Directional Overcurrent Testing

The local Hardware Configurationactivates the outputs/inputs of the CMC test set for the selected testmodule. Therefore, it has to be defined for each test module separately. It can be opened by clicking theHardware Configurationbutton in the test module.

3.3.1 Analog Outputs

3.3.2 Binary Inputs


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3.4 Defining the Test Configuration

3.4.1 General Approach

When testing the non-directional overcurrent protection, the following steps are recommended:

> Pick-up Test: Testing the pick-up value of the overcurrent protection (only if the start contact is wired forthis relay, or if the relay is of the Ferraris disk type see Help for more information).

> Trip time characteristic: Verifying the trip times of every element of the tripping characteristic.

Each of these tests can be performed with the Overcurrenttest module.


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3.4.2 Pick-Up Test

1. For this test, it is not necessary to define a trigger in the Triggertab. The pick-up test can be performed ifa start contact is wired and defined as a test module input signal in the local Hardware Configuration(see chapter3.3 ).

2. Settings in the Faulttab will not be needed in this test (but might be added to combine pick-up andcharacteristic tests in one module).

3. As the start contact is used to trigger this test, Relay with start contacthas to be chosen.

4. The phase overcurrent function is tested with phase to phase faults.

Note:In this case other protection functions may interfere with the test. However, if such functions orelements (e.g., ground fault protection, negative sequence protection, etc.) are present they may bespecified in the Test Objectin the same manner as the phase elements were entered in this example.The resulting characteristic will be calculated individually and shown for each test shot depending on itsfault type (4)and fault angle (5), ensuring a proper assessment according to the expected overall relaybehavior.

5. For the non-directional test, no voltages are used, therefore, no test anglecan be set.

6. As the pick-up is not delayed, a step length (Resolution) of 50 ms should be sufficient.

Note: The pick-up value will be measured and assessed automatically. The drop-off value will also be

measured, but it will not be assessed. The assessment of the drop-off value and of the resetratio has to be made manually.

More test lines can be added if needed, e.g., different fault types.

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3

4 5 6


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3.4.3 Trip Time Characteristic Test

Triggerand Faulttabs:

1. The trigger for this test will be the trip contact.

2. A Load currentduring the pre-fault state will not be used in this example.

3. The Absolute max. timehas to be adjusted. On the one hand, it has to exceed the upper tolerance ofthe test point with the longest trip time otherwise an assessment will not be possible. On the other hand,it should not be set to an unnecessarily high value. For shots where No tripis expected this will be thewaiting time until the assessment 'no trip' is made before continuing with the next shot. So if this time isset to a very high value, it would unnecessarily prolong the test duration.

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Characteristic Testtab:

1. As the function to test is a phase overcurrent function, a phase to phase fault is used.

Note:In this case other protection functions may interfere with the test. However, if such functions orelements (e.g., ground fault protection, negative sequence protection, etc.) are present they may bespecified in the Test Objectin the same manner as the phase elements were entered in this example.The resulting characteristic will be calculated individually and shown for each test shot depending on itsfault type (1)and fault angle (2), ensuring a proper assessment according to the expected overall relaybehavior.

2. The Anglecannot be set because no voltages are used.

3. As the trip time of the IDMT element depends on the current, this element has to be verified with morethan one test point.

4. The trip time of the 2nd

element can be confirmed with only one test point.

5. The value of the 2nd

element is also confirmed by placing two test points outside of the tolerance band ofthis setting.Instead of directly entering the magnitude value it can be expressed by its relation to an element setting,e.g., set Relative to:to the 2

ndelement and set the Factorto 1.06 (i.e., 6 % above the threshold) or 0.94

(i.e., 6 % below the threshold).

Feedback regarding this application is welcome by email [email protected].

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