Presentation on Pump Turbine No.1

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PRESENTATION ON PUMP TURBINE NO.1

SUDANESE HYDRO POWER GENERATION COMPANY LTD.

KASHEM EL-GIRBA HYDRO POWER PLANT

COMPILED BY CONSULTANT ENGINEER SALIH AHMED OBEID SALIH15/4/2015FROM 21/8/2014 UNIT WAS SHUTDOWN DUE TO THE FREQUENT HIGH TEMPERATURE OF THE OIL HEAD AND COULD NOT BE OPERATED FOR LONG TIME AND SO IT WAS LEFT OUT OF SERVICE FROM THAT TIME WAITING FOR THE PROVISION OF THE REQUIRED SPARE PART THE SPARE PART WAS RECEIVED ON MARCH 2015THE MECHANICAL STAFF OF THE POWER STATION DID THEIR BEST AND INSTALLED THE REQUIRED SPARE PART AND THE UNIT WAS MADE READY FOR OPERATIONWHEN THE UNIT WAS MADE READY FOR SYNCHRONIZATION IT TRIPPED BY MEANS OF 1-OVERCURRENT PROTECTION2-EARTH FAULT PROTECTION THESE ALARMS WERE ACCOMPANIED BY A VERY HIGH SOUND OF THE C.BTHEN ANOTHER TRIAL WAS MADE AND THAT TIME IT TRIPPED AGAIN BY MEANS OF DIFFERENTIAL PROTECTION AND THE SHEAR PINS OF THE COUPLING OF THE GENERATOR WERE FOUND BROKEN.THE POWER STATION STAFF WERE TOLD NOT TO OPERATE THE UNIT TILL THE ARRIVAL OF THE PROTECTION ENGINEER OUR PROTECTION ENGINEER WAS SENT TO KASHMEGIRBA TO CHECK AND SOLVE THE PROBLEMTHE STATOR WINDINGS OF THE GENERATOR WERE TESTED BY AN INSULATION METER AND WERE FOUND VERY GOOD AND THE PROTECTIVE DEVICE WAS ALSO CHECKED..ON THE TRIAL OF SYNCHRONIZING THE UNIT,IT WAS SYNCHRONIZED AND LOADED FOR MORE THAN 15 MINUTES AND FOUND TO BE OK.THEN THE ROTECTION ENGINEER ARRIVED AT KHARTOUM AND REPORTED (OK )CONDITION

WHEN THE PROTECTION ENGINEER ARRIVETD AT KHARTOUM AND AFTER SOME DAYS THE UNIT WAS AGAIN OPERATED AND THAT TIME IT WAS FOUND TO TRIP BY THE DIFFERENTIAL PROTECTION AND THE COUPLING SHEARPINS WERE FOUND BROKEN AGAINTHE GENERATION DIRECTORATE MANAGER WITH HIS SENIOR STAFF ARRIVED AT ELGIRBA TO CHECK AND FIND SOLUTION TO THE PROBLEMS OF THE PUMP TURBINE AS FEAR CAME FROM THE LONG TIME OF THE STANDSTILL DURATION AND THE HUMIDITY AND CONDENSATIONON ARRIVAL THERE A TEAM FROM CONTROL AND INSTRUMENTATION SECTION WAS ALREADY THERE WITH COMMERTIAL ADMINSTRATION ENGINEER ON A JOB OF CALIBRATION AND CONNECTION AND INSTALLATION OF NEW ENERGY METER FOR STATION AUXILIARY TRANSFORMER (AT1).SO ALL OF US MADE AN INSULATION MEASUREMENT OF THE PUMP STATOR WINDINGS AND IT WAS FOUNK OK.THE UNIT WAS TESTED AGAIN FOR STATOR WINDING INSULATION MEASUREMENT AND THE RESULT WAS FOUND OK. (6 GEGA OHM)AN ATTEMPT WAS MADE TO DRY THE UNIT BY MEANS OF AN EXTERNAL DC SUPPLY AS AN EXCITATION SOURCE AND SHORT ALL THE STATOR WIRES BY COPPER BAR AND THE UNIT TO OPERATED TO ITS RATED SPEED AND APPLY THE EXCITATION SUPPLY GRADUALLY TILL WE GET ITS RATED CURRENT AND BY DOING SO WE WILL BE SURE THAT THE UNIT IS TOTTALLY DRY AND NO MOISTURE WILL BE THERE

THE TRIAL OF DRYING THE UNIT COULD NOT BE DONE ALTHOUGH THE JUMPERS WERE MADE DUE TO DIFFICULTY OF FINDING CLEAR DRAWINGS AND THE INTERLOCK SYSTEM WHICH WAS MADE BY THE CONTRACTOR (BE,SC,SIEMENS PLC S7,MECHANICAL INTERLOCK,PROTECTION INTERLOCK,AC SUPPLY INTERLOCK ,DC SUPPLY INTERLOCK)WAS TOO MUCH COMPLICATED AND NOT EASYIT IS WORTH MENTIONING THAT STARTING OF THE UNIT IS TOO DIFFICULT BESIDE THE GOVERNOR AND HYDRAULIC TROUBLES AND IT SHOULD BE MADE EASY AND SIMPLE

THE PUMP TURBINE NO.1 WAS OPERATED AFTER DIFFICULTY AND WAS SYNCHRONIZED BUT IT TRIPPED IMMEDIATELY BY THE DIFFERENTIAL PROTECTION SO IT WAS DECIDED TO REPLACE THE PROTECTION DEVICE BY ANOTHER ONE FROM UNIT 3 AND AFTER THAT THE UNIT WAS SYNCHRONIZED WITH NO ALARM BUT IT WAS NOTICED TO HAVE A HIGH SOUND ON THE CIRCUIT BREAKER CLOSURE AND WE WERE NOT HAPPY TO THAT SOUND ,BUT THE MECHANICAL ENGINEERS SAID IT CAME FROM THE RUNNER BLADES OPENING HYDRAULIC SYSTEMTHE UNIT WAS LOADED UP TO 300 KW AND IT WAS OBSERVED TO FIND THAT THE TEMPERATURE SENSOR OF THE GEAR BOX WAS NOT GIVING ANY INDICATION ON THE PANEL AND THE UNIT WAS STOPPED FOR FURTHER CHECKING AND MAINTENANCE AND INVESTIGATIONTHE SENIOR STAFF WITH THE GENERATION DIRECTORATE MANAGER LEFT FOR KHARTOUMAFTER SOME DAYS WE WERE REPORTED THAT PT1 WAS OPERATED AND WAS FOUND TO TRIP BY FIFFERENTIAL PROTECTION ACCOMPANIED BY BROKEN SHEARPINS OF THE COUPLING.INVESTIGATION10ANOTHER TEAM WAS AGAINT SENT TO KASHMELGIRBA FOR FURTHER STUDY AND INVESTIGATION AND SOLUTION TO THE PROBLEMIT WAS DECIDED THAT THE PROTECTION ENGINEER TO CHECK ALL THE CURRENT TRANSFORMERS AND THE CONTROL ENGINEER TO CHECK THE SIEMENS PLC PROGRAMME AND FEAR WAS CLEAR THAT TIME THE C.B SHOULD BE RACKED OUT AND THE TEAM CAME TO DECIDE WETHER THE C.B CLOSURE IS CORRECT OR NOT AND ALL OF US ARE AFRAID OF WRONG SYNCHRONIZATION OR C.B DELAY TIMEA PROPOSAL 11THE PROTECTION ENGINEER TESTED ALL THE CURRENT TRANSFORMERS AND THEY WERE FOUND TO BE OK.THE CONTROL ENGINEER TESTED THE SIEMENS PLC AND INDICATEDT HAT NO SIGNAL OF CLOSING THE C.B IN PUMPING MODE COULD BE GOT IN GENERATION MODETHE C.B WAS PUT IN RACKED OUT POSITION AND SOME WIRES WERE USED TO SIMULATE IT IN RACKED IN POSITION BUT THAT PROCEDURE FAILED AND THE C.B COULD NOT BE CLOSEDTHE C.B WAS AGAIN PUT IN RACKED IN POSITION BUT ITS CLOSING COIL WAS DISCONNECTED AND THE PROTECTION ENGINEER WAS REQUESTED TO BE NEAR THE C.B SO AS TO HEAR THE SOUND OF THE CLOSING RELAYAN INDICATION LAMP WAS CONNECTED ACROSS THE SIGNAL LOCATION SO AS TO SEE EXACTLY THE TIME OF THE CLOSING SIGNAL.

THE IDEA WAS MADE IN ORDER TO CHECK THE EXACT SIGNAL CLOSURE WITH RESPECT TO ALL THE SYNCHRONIZING DEVICES WHICH ARE1-AUTOMATIC SYNCHRONIZING UNIT( SCK4N)2-RUNNING VOLTAGE3-INCOMING VOLTAGE (GENERATOR)4-SYNCHROSCOPE DEVICE5-RUNNING FREQUENCY6-INCOMING FREQUENCY (GENERATOR) THE TEAM DID THEIR BEST TO OPERATE THE UNIT AND THE TEST WAS DONE WHERE THE LAMP WAS FOUND TO BE ILLUMINATED ALL THE TIME AND THE SYNCHROSCOPE WAS RUNNING FROM SLOW TO FAST AND FROM FAST TO SLOWWHILE DOING SO AND OBSERVING THE SITUATION THE LAMP WENT OFF WHEN THE SYNCHROSCOPE WAS SEEN POINTING 180 DEGREE FROM THE (S) POSITION AND ALL OF US WERE SURPRISED OF THAT CONDITION WHERE IT WAS DICOVERED THAT THE SYNCHRONIZING WAS DEFECTIVE(SCK4N)THEN IT WAS DECIDED TO REPLACE THE FAULTY DEVICE WITH THE ONE OF UNIT 3 AND ALSO TO REPLACE THE C.B WITH THAT OF PT3THE UNIT WAS OPERATED AND WAS SYNCHRONIZED SMOOTHLY AND IN GOOD CONDITION WITHOUT ANY PROBLEM WHILE DISCOVERING SUCH AN ODD PROBLEM WHICH HAPPENED TO US FOR THE FIRST TIME. SINCE WE NEVER THINK OF HAVING THE SYNCHRONIZING DEVICE TO BE ITSELF DEFECTIVEON A RECENT STUDY FOUND ON THE WEB (http://www.emo.org.tr/ekler/8c83e21f7df5abe_ek.pdf) .THE REASONS OF THE OUT OF PHASE SYNCHRONIZATION ARE:1-WRONG WIRING OF THE SYNCHRONIZING DEVICE DURING COMMISSIONING OR MAINTENANCE2-DELAY TIME OF THE C.B CLOSURE WHEN A CLOSING SIGNAL IS OBTAINED3-C.B CONTACTS FAILURE OR FLASH4-WRONG SETTING ON THE SYNCHRONIZING DEVICEAS A REMINDER SYNCHRONIZING IS ONLY POSSIBLE IF AND ONLY IF WE GET THE FOLLOWING CONDITIONS1-VOLTAGE MAGNITUDE IS EQUAL FOR BOTH RUNNING AND INCOMING2-FREQUENCY IS THE SAME FOR BOTH RUNING AND INCOMING 3-PHASE ROTATION ARE THE SAME FOR BOTH RUNNING AND INCOMING (RST,OR RYB SYSTEM)4-THE PHASE ANGLE ARE THE SAME FOR BOTH RUNNING AND INCOMINGPOOR SYNCHRONIZATION CAN MAKE: Damage the generator and the prime mover because ofmechanical stresses caused by rapid acceleration ordeceleration, bringing the rotating masses intosynchronism (exactly matched speed and rotor angle)with the power system. Damage the generator and step-up transformerwindings caused by high currents. Cause disturbances to the power system such as poweroscillations and voltage deviations from nominal. Prevent the generator from staying online and pickingup load when protective relay elements interpret thecondition as an abnormal operating condition and tripthe generator.SYNCHRONIZING DEVICE

IT IS WORTH MENTIONING THAT SYNCHRONIZATION CAN BE DONE BY ONE OF THE FOLLOWINGS1-BY MEANS OF LAMPS (DARK &BRIGHT LIGHT) WITH MANUAL CLOSING OF THE C.B2-MANUAL CLOSING OF THE C.B WITH THE HELP OF SYNCHROSCOPE3-CLOSING THE C.B BY MEANS OF CONTACTS FROM THE SYNCHROSCOPE4-CHECK SYNCHRONIZING RELAY5-AUTOMATIC SYNCHRONIZING DEVICETHANKE YOU FORYOUR ATTENTION