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WRITE UP

ON

AUTOMATIC TURBINE TESTER

Consultant: DEVELOPMENT CONSULTANT PVT. LTD.TYPE OF PRODUCT : TG

NAME OF CUSTOMER/PROJECT: 4X600 MW O.P.JINDAL STPP PHASE-III

NAME SIGN DATEDRN. SHEETAL Sd/- 23.09.09CHD. V.KUMAR Sd/- 23.09.09

BHARAT HEAVY ELECTRICALSLTD.

APPD. K.B.BATRA Sd/- 23.09.09

NO.OFVAR.

DEPT.

CODE.

CIE4180

SCALE WEIGHT(KG) REF.TO ASSY.DRG. ITEM NO.

NO. OFITEMS

DOC. No. 4-18000-76-416 REV.00

TITLE: WRITE UP ON AUTOMATICTURBINE TESTER

CARDCODE

SHT.NO 01 NO. OF SHT. 14

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Reference Documents :

(i) Automatic Turbine Tester Logic Diagrams(ii) Write-up on Automatic Turbine Run up System(iii) Governing Scheme

NOTE: This document is explanatory write-up of document no. (i) mentioned above.

1.0 GENERAL:

The safety devices (protective devices) protect the turbine from impermissibleoperating conditions. On response of a safety device, the HP & IP stop valvesclose. Closure of control valves is initiated by secondary fluid pressure reduction.

The Automatic Turbine Tester is used to check / test at a regular interval thefunction of the safety devices of the turbine and its 'stop and control valves',while it is in operation, without causing actual turbine trip.

The Automatic Turbine tester has been divided into two sub-groups viz.

(i) Sub-group Safety Devices.(ii) Sub-group HP/IP valves.

Each sub-group is further sub-divided into sub-tests for each individual devicecovered under the sub-group. The switching on of the sub group control andsubtests shall be in the following modes.

1.1 The selection of the sub-group and sub-test shall be manual from OWS in

control room.1.2 Both the sub groups are so interlocked that operation of only one subgroup shall

be possible at a time.

1.3 Any of the subgroups can be switched ON or OFF of the concerned SGC by thecontrol buttons for SGC- ON/OFF in OWS. As a result, the display AUTO ONwill glow in CRT.

1.4 Any one subtest of the switched-on subgroup can now be selected by clickingthe concerned control button 'SELECTION ON'. As a result, the lamp 'DEVICERELEASED' shall glow on the corresponding CRT display. The individual sub-testselection are also mutually interlocked, so that only one selection and hence onesub-test can be executed at a time. The selection can be cancelled by clickingthe control button 'SGC ON/OFF'.

1.5 After a subtest has been selected, the subgroup program shall be started byclicking the control buttons for START UP in OWS. If the initial conditions forthe test are fulfilled, the display (in CRT) `PROGRAM RUNNING` will glow.

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Otherwise the subtest will be blocked and the missing initial conditions will beindicated in code form on the criteria display.

1.6 The momentary status of the test program shall be indicated by means ofvarious text displays in CRT. The test program in progress can be interrupted atany time by clicking the control button for SHUT DOWN from OWS.

1.7 Once started, the testing cannot be switched over to another subtest or the SGCcannot be switched off, before the program selected has been completed. If asubtest selected has been completed successfully the display `TEST COMPLETEDSUCCESSFULLY' shall glow and the reset program shall start automatically.

1.8 If a fault e.g. "Running time exceeded" is detected during a test, the respectivepretest or main test shall be discontinued immediately and the shut down i.e.reset program be started automatically. The missing criteria and concerned stepnumber shall be indicated on the criteria and step display indications. Faultalarms can be acknowledged by clicking upon the display button 'SGC ON/OFFonly.

1.9 If the test of a selected subgroup is completed successfully, either anotherselection is made and test program started again, or the subgroup control isswitched off manually from OWS.

2.0 SUBGROUP `SAFETY DEVICES'

The Automatic Turbine Tester for the 'Safety Devices' consists of the followingsub-tests: -

(i) Remote Trip Device 1 i.e. Solenoid valve 1 (MAX52 AA001).(ii) Remote Trip Device 2 i.e. Solenoid valve 2 (MAX52 AA002)(iii) Over speed Trip Device (MYA10AA001. / MYA10AA002).

During normal trip the 'Safety Devices' close the stop valves of HP & IP, via the'Tripping Devices (MAX51AA005+006). The remote Trip Solenoid valves 1+2actuate the 'Tripping Devices' by stopping the supply of control fluid to them andopening the trip fluid circuit to drain simultaneously. All other 'Safety Devices'operate on the 'Tripping Devices' by opening the auxiliary trip fluid circuit todrain.

An alternative trip fluid circuit is established for the duration of testing of the'Safety Devices' in order to protect the turbine during testing. In this case bymeans of the change-over valve (MAX51 AA211), the trip fluid circuit is isolatedfrom the `Safety Devices' and supplied with control fluid via the test tripsolenoid valves 1&2 (Remote Trip Solenoid valves during test), MAX51 AA201 +202.

In order to ensure complete protection for the turbine, emergency tripconditions during testing cause the solenoid valves MAX51AA201 + 202 to be

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de-energized resulting turbine trip and the reset program to be startedsimultaneously. During testing, two limit value monitors provide over speedsignal for protection of turbine against actual over speed.

The turbine trip is prevented due to Automatic Testing of the 'Safety Devices'but the general annunciations are activated. This allows testing of appropriatepart of the alarm annunciation system also. The Automatic Tester thereofmonitors the timings of all commands and the execution. If the monitoring timeis exceeded, the reset program is started in order to re-establish the initialcondition.

2.1 'Startup' program, SG Safety Devices

The start up program of each subtest is divided into two parts viz. pretest andmain test. If the operator switches on the 'subgroup safety devices' as perclause 1.4 - 1.6, the program would proceed to execute the tests providedfollowing release criteria are present.

(i) Tripping Devices in operating position, and(ii) All the monitors in operating position, and(iii) 'One release' is present (i.e. a selection command is given).

An interlock is provided to switch off the "sub group - safety devices" if "subgroup - safety valves" is already on.

2.1.1 PRETEST

The pretest will be performed before each subtest (MAIN TEST). If this test is

completed successfully it is assured that the protective logic and remote tripdevices during testing are in working order.

Step 1: - In the step 1 a signal is issued to indicate that pretest is 'ON' and twocommands are issued to energize the test trip solenoid valves (MAX51AA201 +202) (Ref. clause 2.5) causing control fluid pressure to build up at thechangeover valve. A similar command will again be issued with the help of signal once the test solenoid valves 1 & 2 are individually tested for successfuloperation in step 2 & 3. Within 4 sec. of wait/check time the pressure at switchMAX51CP208 should be established.

Step 2:-In step 2 a simulated over speed signal is fed to de- energize the 'testtrip solenoid valve 1' (MAX51AA201) (Ref. clause 2.5). This should result indepressurization of the control fluid before the changeover valve. The pressureat switch MAX51CP207 must drop but the pressure at switch MAX51CP206should not change as the 'test trip solenoid valve 2' MAX51AA202 is stillenergized. These check back criteria indicate the healthiness of the solenoidvalve MAX51AA201 as well as speed limit value monitor 1.

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position when the predetermined pressure is reached and operate the trip leverto depressurize auxiliary trip fluid circuit instantaneously. This results in trippingof the Tripping devices 1 and 2 and collapse of the over speed Trip devices andpressure of test oil are also taken as check back criteria for completion of thetest. If the over speed trip devices trip a little earlier before the set test oilpressure builds up to set value, it is annunciated in the panel insert and thereset program started automatically to restore all the devices tripped to theirnormal operating positions.

2.2 Reset (Shutdown) Program: SG-Safety Devices

The reset program is started automatically as soon as any of the main testsdescribed in clause 2.1.2 are over. It is also started under protection in theevent of turbine trip during testing, represented by trip fluid pressure (

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turbine has tripped. This is because of the reason mentioned at para 2.2.2(i)below. Step 51 is also enabled from step 53 for recycling purposes.

2.2.2 Step 52

In this step command is issued to energize the reset solenoid valves MAX48AA201 & 202 so that auxiliary start up fluid is supplied with control fluid whichforces all safety devices viz. Tripping Devices (MAX51AA005 & 006), ManualTurbine Trips (Levers 1&2) and over speed trip devices (MAY10AA001+002), toreturn back to their operating position, and the trip fluid pressure then builds upto normal values. After 6 sec. time which will allow completion of this resettingthe reset solenoid valve MAX48AA201 is de-energized to shutoff the control fluidsupply through it and thus cause pressure at MAX48CP201 to drop. Theadditional 4 sec in the waiting time has been envisaged to allow sufficient timefor the establishment of this check back criterion for signal to enable step53.

The check-backs are bypassed in the case of reset program due to turbine tripor exceeding of running time for the following purposes (i) & (ii):

i) In the event of turbine trip during test, the pretest or main test is discontinuedimmediately and the reset (shutdown) program started under protection. In thereset program only ' over speed trip device' is restored to its operating positionso that the turbine can be restarted with the over speed trip device in its normaloperating position.

ii) If the running time of the pretest or a main test exceeds (due to non-fulfillment of astep criterion), the pretest or main test currently running is discontinued and the

reset program started under protection to restore the normal operating position.If the running time exceeds during reset program the respective step is held upand the resetting can be restarted again, to repeat the resetting when themissing criterion is made available.

The fault causing the running time to exceed is to be eliminated immediatelykeeping the turbine monitoring equipment under observation.

2.2.3 Step 53:

As soon as the step 53 is enabled the reset solenoid valve MAX48AA202 is de-energized and the auxiliary start up fluid pressure between the two resetsolenoid valves also collapses which is taken as one of the check back criteria.The other check back criteria are the same as those of step 52. Here againwaiting time and all check-back criteria are bypassed in case of resetting due toturbine trip [ref. para 2.2.2(i)]. Also ref. Para 2.2.2 (ii) for the requirement ofmanual resetting.

2.2.4 Step 54

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In this step command is issued to close the solenoid valve MAX61AA201 byreenergizing it. This closes the drain port and control fluid pressure builds upwhich pushes the changeover valve to its normal working position. Additional 3sec. in waiting/check time has been provided for ensuring trip fluid pressurebuilding to normal value through tripping devices. The status indication of'change over valve' in test position is also removed. Another command is issuedhere simultaneously to reset all the memories to register cancellation of all theselection.

2.2.5 Step 55

In this final step, after change over valve has changed to normal workingposition,commands are issued to de-energize the remote trip test solenoids 1 & 2(MAX51AA201 & 202), by resetting the memory circuits. This is the last step ofreturning to normal operating conditions and the check back criteria are thecollapse of pressure of the control fluid between the remote trip test solenoidsand before the changeover valve. The program remains stay-put here byresetting the memory, unless the sub-group is switched off or unless anothersub-test is initiated. The status indication "resetting on" is also removed aftergetting the check back criteria.

2.3 ATT Selections: Safety Devices:

2.3.1 The released signal for any of the safety devices, to be used as one of therelease criteria for start-up program as well as enabling criteria of the respectivemain test, shall be generated if all of the following conditions are present:

(i) The push button 'selection on' on the panel insert of the concerned safety deviceswitched-on.(ii) Main test of the respective sub-test not at its end.(iii) None of the safety devices released.(iv) Sub group safety devices switched-on.

2.3.2 The released signal shall be reset (removed) if any of the following conditionsare present:

(i) 'Released' signal for any other safety device present.(ii) 'SGC ON/OFF' push button of sub-group safety devices pressed and the test

program is not running.(iii) Command from step 56 issued.

2.3.3 The memories for release signal generation for testing of "speed limit valuemonitors" at the time of PRETEST [ref. clause 2.1.1 (step 2&3)], are set fromthe signals of step 1 & step 3. They are reset by completion of individual testingor by command from step 51.

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2.4 ATT Annunciations (Safety Devices):

2.4.1 Signals 'Change over valve test position', 'one or more monitors tripped','remote trip during test on' and 'trip devices resetting on' shall be generated forannunciation on the respective text display tiles of panel insert, provided sub-group is switched on and the devices are in the respective conditions.

2.4.2 Separate signals as applicable representing completion of main test of respectivesafety devices are issued for indication 'Test completed successfully' on therespective tiles of panel insert as well as for the purpose of interlock as perclause 2.3.1(ii). These signals shall continue to persist unless the memories arereset by switching off the sub-group control.

2.4.3 Signals for indicating 'pretest', 'Main Test', 'Resetting' and 'fault' conditions atthe text display tiles of MMI and signal representing trip by over speed duringtesting for central annunciation are generated. These are described below.

2.4.3.1 The signal 'Pretest ON' shall be generated by setting the memory due tocommand from step 1. The signal shall persist unless the memory is reset byany one of the following conditions: -

i) Pretest end.ii) Command from step 51 issued.iii) Subgroup control is switched off.

2.4.3.2 The signal 'Main Test On' shall be generated if pretest is completed or the maintest of valves is on (ref. clause 3.4). The signal shall persist unless the memoryis reset by command from step 51 and the 'Main Test valves ON' signal memory

is reset by command from step 51 of sub-group valves.2.4.3.3 The signal 'resetting ON' shall be generated by setting any of the memories by

command from step 51 of the respective subgroups (also ref. clause 3.4). Thesignal shall persist unless both the memories are reset by signal issued afterrespective resetting is complete. The memory will also reset if SGC is switchedoff.

2.4.3.4 If the turbine is tripped during testing or running time is exceeded, a 'fault'alarm is generated, which disappears on acknowledgement by pressing "SGC -ON/OFF" control pushbutton.

2.4.3.5 The signal 'Trip by over speed during test' shall be generated if turbine speed,sensed by any or both of the speed limit value monitors exceeds 110% whilechangeover valve is in test position.

2.5 ATT turbine trip during test: channels 1 & 2

The two commands 'Control Fluid provide' issued at step 1 will set two separatememories to issue separate commands to energize the test solenoid valves

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(MAX51AA201 & 202), if the turbine speed, sensed by the speed limit valuemonitors 1&2, is less than 110% or the release for testing of speed limit valuemonitor is present.

On successful completion of testing of speed limit value monitors in step 2 & 3of PRETEST, a signal is fed to de-energize the test trip solenoid valvesMAX51AA201 & 202, and the memories to reset.

After step 4 the two commands 'Control Fluid provide' are again issued whichwill energize the two test solenoids. The two solenoids will remain energized andthe two memories will continue in set position to ensure turbine protectionduring testing.

The memories will reset and the test solenoid valves de-energized, if any of thefollowing conditions are present: -

i) Command from step 55.ii) Respective Electrical Turbine Trip is operated.iii) Actual turbine speed, sensed by the respective speed limit value monitor

crosses the limit i.e. 110 %.iv) Respective manual Turbine Trip is operated.

The conditions (ii) through (iv) mentioned above shall cause the turbine to trip.

3.0 SUB GROUP 'HP/IP' VALVES:

The 'Stop and Control Valves' are the final control elements of the 'SafetyDevices' and hence their serviceability is just as important as that of 'Safety

Devices' themselves. The testing of these valves in conjunction with the safetydevices ensures that all elements, which must operate if an emergency trip isinitiated, has been fully tested for serviceability.

There are 2 combined HP stop valves and control valves and two combined IPstop valves and control valves. They are grouped together to the selector pushbutton tiles for individual testing to form following sub-tests: -i) HP stop and control valve -1ii) HP stop and control valve -2iii)IP stop and control valve -1iv)IP stop and control valve -2

Following tests are performed :a) Test of HP & IP control valves for freedom of movement.b) Functional check of HP and IP stop valves.c) Check of maximum permissible closure time of HP & IP valves.

The test procedures for all valve combination are identical and hence there is acommon program, actuating and testing any combination depending uponmanual preselection and permissible conditions prevailing.

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All testing equipment is part of the trip fluid system, which is depressurized inthe event of a trip. Thus in the event of an actual turbine trip during testing, theclosing of valve is no way effected regardless of the stage of testing reached.This is also applicable for control valves because there is no interference withthe secondary fluid circuit and therefore, the pressure there can be reducedwithout difficulty.

3.1 Start -up program: sub-group HP/IP valves

If the operator switches on the 'subgroup HP/IP valves' as per clause 1.4 - 1.6,the program would proceed provided the following release criteria are present:i) Release for testing of any one valve combination is present.ii) Unit load is less than a particular value (80 %).iii) All the stop valves are 100 % open.iv) Load controller is in action.

An interlock is provided to switch off the 'sub-group HP/IP valve' if 'sub-groupsafety devices' is already on.

3.1.1 Step 1: Closing of the Control Valve

In this step, a command is issued to the control valve actuator motor of theselected stop & control valve combination from HP/IP valves, to close the controlvalve. The motor acts on the feedback system of the servomotor, and producesa closing action. The closure is slow and steady, as necessitated for maintainingconstant load by Electro hydraulic Controller, which opens the other valvecombination as per requirement. The motor continues to run until the limit

switch indicates complete closure of the control valve. i.e. zero position whichenables step 2. A stroking time applicable for the valve is used as monitoring(check) time.

A signal from this step is also used to generate the signal "Main test: valves -ON.

3.1.2 Step 2: Closing of the Stop Valve

In this step, a command is issued to energize the stop valve of the selected stop& control valve combination from HP/IP valves. The solenoid valve causes thetrip fluid supply to be interrupted through it, and drains the fluid under the stopvalve piston disc immediately. As soon as the pressure falls slightly below thepiston parting pressure, monitoring of the stroking time of the valve begins instep 3.

3.1.3 Step 3: Monitoring of the SV closure time

This step monitors the time taken by the selected stop valve to close. It shouldclose within 0.2 seconds. A successful closure marks the end of the "Partial test"

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- i.e. testing of one HP/IP valve combination. Automatically the "reset program"is initiated and the end of a test annunciated through the corresponding controldisplay "Test completed successfully".

3.2 Reset (Shut down) Programme 'sub-group' HP/IP Valves:

The reset program is started automatically as soon as a partial-test, asdescribed in para 3.1.1 - 3.1.3, is over. It is also started under protection if the'Running time' is exceeded in any of the main tests or the turbine trips duringtesting.

In this program the stop and control valves, which had been closed during themain test, are returned to the operating position. However, if the reset programis initiated by turbine trip then in the reset program only the control valveactuator is reset at step 55, and other steps are bypassed.

The signal starting the reset program under Automatic action gets reset as soonas a reset step is set, so that startup program can be restarted for othersubtests or when needed.

3.2.1 Step 51

In this step, the memory of 'Main test valve' ON is reset (ref. clause 3.4 below)to stop 'Main Test' on indication on the panel (ref. clause 2.4.3.2). The signal"resetting on" is generated and annunciated in the panel insert (ref. clause2.4.3.3).

The bypass condition of the waiting time is applicable when the concerned stop

valve is already open up to 100%.3.2.2: Step 52

In this step command is issued for tightening of the spring between the pistonand the piston disc, of the selected stop valve. The reset solenoid valveMAX47AA211 etc. is energized to move the test valve MAX47AA011 (or itsequivalent in other valve combination) to its test position and allow trip fluid topress over the piston and compress the spring till the piston seats on the disc.This causes a rise in pressure (>6 kg/cm2) above the piston and indicatescompletion of preloading of the servomotor. This condition gets stabilized withinthe waiting time of 40 seconds, and then the program proceeds to step 53. Butif the selected stop valve is already open or the turbine is tripped, then thiswaiting time is by passed.

3.2.3 Step 53

In this step, a command is issued to de-energize the test solenoid MAX61AA211(or its equivalent in other valve combination) of the stop valve of the selectedvalve combination, to allow trip fluid to flow below the piston of stop valve,

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through the test valve. The check back criteria is the building up of pressure inthe trip fluid line between the test solenoid and the test valve.

The check back criteria and the waiting time are bypassed if the concerned stopvalve is already open, or if the turbine has tripped.

3.2.4: Step 54

In this step commands are issued to open the stop valve by de-energizing thereset solenoid valve and the test solenoid valve to drive them to operatingpositions, which make the test valve (MAX47AA011 etc.) to go back to its initialposition and allows the fluid pressure above the piston of the stop valve todrain. The resultant pressure differential causes the pre-loaded piston/pistondisc unit to open the stop valve to 100% position.

A deliberate waiting time had been envisaged to take care of the time requiredfor smooth building up of the pressure. Again this waiting time is bypassed if theturbine trips during testing.

3.2.5: Step 55

After the stop valve has opened up to 100%, the concerned control valve is

actuated to open by driving the actuator in the open direction. Operating on thefeedback of the control valve servomotor, this causes the control valve to bereturned to a position corresponding to secondary fluid pressure. Here again,the load is kept constant by the EHC acting on the other SV/CV combination, atthe same time. The motor continues to run until the actuator is brought to

normal position sensed by the limit switches as check back criteria. The strokingtime of the valve is also used here for monitoring satisfactory operation of thisstep of the reset program.

3.2.6: Step 56

This step is set after the resetting is successfully completed and here themonitoring time is blocked and the program remains stay put. An interlockcancels the selection (release) by resetting the memories and removes theresetting on annunciation on the panel insert (ref. clause 2.4.3.3). If anothersubtest is selected the program runs again, or else sub group control is switchedoff.

3.3: ATT Selection valves

3.3.1 The 'Released' signal for any of the valve combinations are generated/canceledin the same way as done for safety devices (ref. clauses 2.3.1 and 2.3.2).

There is one more interlock for the testing of IP valves. The "release" signal forIP valves are cancelled if the "secondary fluid pressure to IP control valves",

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becomes less than 5 Kg/cm 2. This condition ensures that the testing of IP canonly be done if both the IP control valves are fully open.

3.2.2 Separate signals, as applicable, representing completion of main test ofrespective valve combinations are issued for indication 'Test completedsuccessfully' on the respective tiles of panel insert as well as for interlock forissuing 'released' signal. The signals shall continue to persist unless thememories are reset by switching off the sub-group control.

3.4 ATT Annunciation valves

If the turbine trips and both the HP-Stop valves are closed the disconnectionrelays are energized to de-energize the turbine trip relays. Turbine trip isrepresented by trip fluid pressure < 2 Kg/cm2. The signal Main Test Valves ONis generated once the testing starts. This signal disappears as soon as theresetting starts and the signal "Resetting valves ON" is generated. These signalsare further utilized to generate the signals "MAIN TEST and "RESETTING" on,as written in clause 2.4.3.2 and 2.4.3.3.

Note:1. All control tiles for ATT (mentioned above) shall be realized in MMI

for control and testing from CRT/KBD.2. ATT logics shall be realized in hot redundant processor.