gas turbine lecture (logics).doc

7/27/2019 Gas turbine lecture (LOGICS).doc

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GAS TURBINE INTERLOCKS,INTERLOCKS ,PROTECTION

and

TROUBLESHOOTINGOF GAS TURBINE

Introduction

Kawas is combined cycle Power plant having 4 GTs along withassociates WHRBs and !Ts

"ontrol system o# Gas Turbine is !peedtronic mar$%I& which is G'design(GT !)*'T+ "H'"K!

Be#ore "ontrol system issues the order to start the GT, it will chec$series o# !a#ety re-uirement #or the GT(

When all chec$s are .K then it will display Ready To !tart message tothe .peratorGas turbine start up chec$s "ompressor Inlet thermocouple%"TI/ 0 1 are within 02(4 deg "( IG& position is 3 20 deg and 25 deg( 604H/ is 7rop i(e(( !peed is 8(5 9 6ub oil Temp :ormal ;< =:> .verspeed bolt is Reset(Gas turbine start up chec$s

:o #lame is present &entilation relie# damper is open( Trip oil pressure is .K ;

7iagnostic Tests are .**Gas Turbine !tart Ap "hec$sIn case o# Gas #uel selection% !top ratio valve position is more then %5(0 9 and less then 5(09 !ervo current is less then %2 ma


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Gas control valve position is more then %@(0 9 and less then 5(CC9 !ervo current is less then %2(C ma Inter valve pressure is more then %C(55 barGas Turbine !tart up "hec$sIn case o# li-uid #uel selection%

6i-uid #uel #low voltage is more then %C(5 vdc and less then DC(5vdc !ervo current is less then %C(5 ma &alve position is more then %(2@ 9 and less then 0C9( )ll communication lin$s are .K&ibration !ystem Healthiness I# all vibration sensors o# GT or Generator are #aulty or disabled , it willissue :ormal !E7( 'ach sensor is monitored through 6imit value monitor( When sensor isshowing less then C( mmEsec, it declares #aulty()uto Trans#er o# *uel

Gas turbine can run on B)!' load with #ollowing #uelF Natural gas

HSD

NGL/naptaTrans#er *rom Gas to H!7 Gas Pressure 6ow !etting at 0(@ bar #alling( Gas Purge valves improperly close( This is derived #rom inter valvepressure switch which is set at 45 psi(

Trans#er *rom :G6Enaphtha to H!7 :ap pressure low( 6ess then 4 bar( :ap tan$ level low( High%tech tan$ level low( :o Hightech pump running( )tomising air di##erential pressure low( ;0 bar> &entilation trouble Telltale lea$age( :ap #low low ;(5 $gEsec> " #ailure :ormal shutdown(Trans#er *rom H!7 to :G6Enaphtha H!7 tan$ level low(

!hut 7own There are two ways to stop the machine in case process parameter goes

out limit or mal#unction( :.R/)6 !T.P( In this mode #uel is gradually reduced and machine isunloaded and put to turning gear( !tress will be less in this mode(


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'/'R'G':"+ !T.P ( In this mode #uel is immediately stop( !tress willbe HIGH in this mode

ac$ing .il Trouble This protection is chec$ing #or healthiness o# Jac$ing oil system( I# Jac$ing oil pressure is low or pump not running it issues the

shutdown order( This protection is applicable only i# speed is less the @(4 9 and sha#t isnot at rest(

6oad Tunnel Temp High *or monitoring temp( .# load tunnel one thermocouple is provided%TTIB( Be#ore synchronisation i# load tunnel temperature is more then 20deg " it issues the normal stop order( This may occur in case o# #an #ailure or ecessive lea$age #rom ehaustcompartment to load compartment(

Inlet )ir *ilter /onitoring

)t the inlet o# compressor #ilters are provided to have good -uality dirt#ree air( *or monitoring the status o# #ilter -uality, .n line monitoring isprovided through 7P transmitter ( In case #ilter 7P raises to 055CP) ;0, It will issue normal shut down(

Tor-ue "onverter /onitoring Tor-ue converter is provided to have variable power at the accessoriesgear side( In tor-ue converter, drain valve is provided #or draining oil( Withoutpower drain valve is open( I# drain valve is #ound closed with out power, itwill issue normal !E7(

!tarting 7evice /onitoring I# gas turbine is Ready To !tart, control system will issue order to startcran$ing motor I# the sha#t does not brea$ away ; speed C(C< 9 > within 2C secondso# cran$ing motor starting , it will issue normal shut down( This may occur due to either improper adJustment o# tor-ue converteror Gen( bearing li#ting is not enough(

)tomising )ir Temp High To monitor the )tomising air temp one temp switch%< )) is providedin the inlet o# the cooler circuit( I# )tomising air temperature eceed 025 deg " #or more then 0C sec it

will issues the normal stop orderGen( !tator Winding Temp High

In each phase o# generator winding ,two number o# RT7 ;Pt%0CC> areprovided #or temp monitoring I# temperature ready any o# the RT7 rises above 05C deg " the it willissue :ormal !hut down order(

Warren Pump 6ub( "ircuit There are two protection #or 6i-uid #uel pump sa#ety(


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6ub oil tan$ level high( This protection is provided to ta$e care o# seal#ailure( In case o# seal #ailure, #uel will be passing towards 6ub oil side, hencetan$ level may rise( 6ub oil pressure is low ;@5 psi> will result in normal shutdown o# GT

Gas Purge "ircuit /onitoring

!"n GT #s runn#ng $n gas %u"l, gas n$&&l" purg" 'al'"s ar"("pt )l$s"d* B"t+""n the two purge valves ;&)%02%0 1 > one pressureswitch


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In case lub oil pressure low is persisting and any one switch o# pressurevery low is also set turbine will TRIP Both the very low switches are set turbine will TRIP

&ibration Protection

'ach bearing is monitored by vibration sensor;s>( In case vibration level goes above 0( mmEsec, operator will get alarm In case vibration eceed the 5(4 mmEsec, turbine will be automaticallyTRIP

!tart up *uel 6imitationEProtection 7uring start up #uel control is utmost important In case o# gas #uel i# we get the position #eedbac$ o# !top%ratio valve ismore then @(< 9 will trip the machine( This protection is basically given toavoid sudden in rush o# gas in case o# pressure rise( Practically this will happen i# o## base s$id Gas valve is not reset( !tart up Protection%6i-uid *uel

To ta$e care o# ecessive #uel during start up, #uel #low ;*=> iscompared with set point C(< $gEsec( I# #low is higher be#ore #lame scan, it willtrip the turbine This may happen because o# LairM in the #uel circuit( )ir in the #uelcircuit results in higher RP/ o# #low divider( #uel #low calculation is based onRP/ o# #low divider speed(

"ommunicator *ailure I# communicator #ails, operator does not have much monitoringsupport, hence i# during start up i# communicator #ails be#ore 85 9 speedlevel GT will trip to avoid any damage due to lac$ o# in#ormation(

6i-uid *uel 6ow Pressure Trip

I# GT is running on li-uid #uel and li-uid #uel pressure drop below 25 psi;(5 bar> GT will trip(

Gas *uel 6ow Temp Trip Gas #uel temperature at the inlet o# gas turbine is monitored throughthe temp( switch( I# this switch senses the temp low ; 0C deg "> it will trip the GT, i# itrunning on Gas #uel(

Gas !crubber 6evel To avoid any gas contamination carried in the turbine, #inal scrubber isprovided Just be#ore shut o## valve( 7ue to condensation in the scrubber, i# the level o# the scrubber risesabove certain level, gas turbine will trip(

6i-uid 6ea$ 7etection in GeneratorE'citer .ne level switch is monitoring the high level and remaining two aremonitoring very high level(


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In case o# high level detected )larm shall be generated( In case either switch detect very high level it will issue trip order(

HR!G Protection This protection is provided to protect the HR!G in case o# 7ivertordamper #ailed to close when HR!G protection is acting(

Time delay o# 4C sec( is provided(Ha?ardous 6ea$ 7etection To monitor the #uel lea$% Gas and 6i-uid ,detection system is providedin )u( and Turbine compartment( In case lea$ detection 3C 9 o# 6'6, it will generate alarm( In case lea$ detection 34C 9 o# 6'6, it will Trip the GT

Pre%Ignition Trip7uring start up ;:. *6)/'> I#F

*uel !ervo *ault .R 'mergency 7" Pump Ander voltage

It will Trip the GT6ub .il Temp Protection

*or monitoring the lub oil temperature, three Temp switches areprovided( Temp High is set to C 7eg " and Temp &ery High are set at @C 7eg "( In case o# any one switch senses the very high temp and temp highalarm is persisting, it will Trip GT I# both the very high temp switches are set , GT will Trip(

"omp( Bleed &alve Protection

7uring start up, any o# the #our bleed valve is not .P': up to operatingspeed, GT will trip(

.verspeed Protection'lectrical .ver speed F Turbine sha#t speed is eceed the set point %00C9 , GT will Trip( )s a bac$ to the 'lectrical .verspeed protection, /echanical.verspeed Bolt is provided( This bolt is calibrated at 00 9 speed( It Wor$son centri#ugal #orce

Gas Purge 6ine /onitoring

7uring gas #uel #iring, i# either o# the purge valve ;&)02%0 1 > is :ot"lose then GT will trip( This protection is provided to avoid miing o# gas and hot o#compressor discharge(

*lame Protection Gas turbine is having #our nos( o# *lame !canners( To $eep GT running at nos( o# *lame should be present( In case 3scanner does not sense the #lame, GT will Trip .n 6oss o# *lame


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'haust Temp Protection In order to have the better li#e o# the turbine , Temp o# the turbine inletis to be maintained at the design value( To ensure the the TIT within thelimit, temp( re#erence%TTRN is calculated( This re# TTRN is compared with the median ehaust TTN/( I# TTN/ is

higher by 02(8 deg ", Temp High alarm shall be generated('haust High Temp Trip I# TTN/ is more then TTRND(5 then GT will trip on 'haust TempHigh( In case o# TTN/ 3


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gas turbine lecture (logics).doc

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