Generator maintenance
- 2. 2 GENERATOR CLASSIFICATION 1. INDIRECT HYDROGEN COOLING OF STATOR AND ROTOR 2. DIRECT GAS COOLING FOR ROTOR AND DIMINERALISED WATER COOLING OF STATOR 3. DIRECT GAS COOLING OF ROTOR AND STATOR 4. AIR COOLED GENERATOR
- 3. 3 DAILY CHECKS CLEANLINESS OF THE BEARING INSULATION CONSUMPTION OF HYDROGEN GAS SAMPLE IN THE GAS TRAP CLEAN THE BRUSH GEAR WITH DRY AIR INSPECT THE SLIPRING CARBON BRUSHES, PIGTAILS AND SIZE OF THE BRUSHES REACTIVATION OF GAS DRYERS CHECK THE LLD COLLECTION FOR OIL / WATER CHECK THE VENT LINE OF GAS COOLER FOR ANY GAS COLLECTION.
- 4. 4 WEEKLY CHECKS CHECK THE SPRING TENSION OF THE SLIP RING BRUSHES USING SPRING BALANCE(150-200gm/cm2) VIBRATION OF THE BRUSHES FREE MOVEMENT OF THE CARBON BRUSHES IN THE HOLDER START AND RUN THE STAND BY SEAL OIL PUMPS AND STATOR WATER PUMPS. CHECK THE FLOW OF SEAL OIL CHECK THE BEARING VIBRATION USING PORTABLE VIBRATION INSTRUMENT
- 5. 5 MONTHLY CHECKS • CHECK ALL THE BOLTS FOR TIGHTNESS • CHECK ALL THE PROTECTION AND INTERLOCKING CIRCUITS • CHECK THE INSULATION AND SHAFT VOLTAGE OF THE ROTOR SHAFT • POLARITY OF SLIPRINGS ARE CHANGED ONCE IN THREE MONTHS(DONE DURING SHUTDOWN) • CONDITION OF SILICA GEL IN THE GAS DRIER. • MOISTURE CONTENT OF THE HYDROGEN GAS
- 6. 6 WHY OVERHAUL IS DONE ? IT ENSURES NO BREAK DOWNS IN BETWEEN THE OVERHAULS. GENERATOR ARE SUBJECTED TO VARIOUS THERMAL, ELECTRICAL AND MECHANICAL STRESSES. TO INSPECT AND EXAMINE THE EXTENT OF DAMAGE IN VARIOUS PARTS IT IS MANDATORY TO UNDERTAKE CAPITAL OVERHAUL
- 7. 7 SCHEDULE OF OVERHAUL FIRST INSPECTION : 8000 Hours SECOND INSPECTION : 16,000 Hours SUBSEQUENT OVERHAUL : AFTER EVERY 24,000 HOURS TEQUIVALENT = T ACTUAL + Ns x Ts TEQUIVALENT : EQUIVALENT RUNNING HOURS T ACTUAL : ACTUAL RUNNING HOURS Ns : NO OF STARTS Ts 20 HOURS (ADDITIONAL NUMBER OF OPERATING HOURS)
- 8. 8 PRE OVERHAUL ACTIVITIES 1. ENSURE THAT ALL SPARES, CONSUMABLES, SPECIAL TOOLS AND OTHER MATERIALS ARE AVAILABLE. 2. PREPARE PERT / BARCHART. 3. NOTE DOWN THE VARIOUS PARAMETERS OF THE MACHINE AT FULL LOAD. 4. MW, MVAR, HZ, PF, STATOR VOLTAGE & CURRENT, IRON & COPPER TEMPERATURE, COLD GAS & HOT GAS TEMPERATURE. 5. STATOR WATER CONDUCTIVITY. 6. SEAL OIL DIFFERENTIAL PRESSURE , SEAL OIL FLOW & SEAL OIL DRAIN TEMPERATURE. 7. VIBRATION READINGS OF BEARINGS AND SLIPRINGS. 8. BEARING DRAIN OIL TEMPERATURE, AND METAL TEMPERATURE. 9. OIL COLLECTIONS IN LLD, 10. H2 GAS PRESSURE DROP PER DAY. 11. DIFFERENTIAL PRESSURE ACROSS FILTERS AND DIFFERENTIAL TEMPERATURE ACROSS ALL COOLERS. 12. OIL WATER AND GAS LEAK. 13. CONDITIONS OF ALL VALVES IN THE SYSTEM. 14. IOT, SOT AND ET LEVEL. 15. MODIFICATION WORKS TO BE CARRIED OUT.
- 9. 9 PERT CHART EARLIEST START TIME: THE EARLIEST TIME AT, WHICH THE ACTIVITY CAN START GIVEN ITS PRECEDENT ACTIVITIES, MUST BE COMPLETED FIRST EARLIEST FINISH TIME: EARLIEST FINISH TIME IS EQUAL TO EARLIEST START TIME FOR THE ACTIVITY PLUS THE TIME REQUIRED TO COMPLETE THE ACTIVITY LATEST STATING TIME: LATEST FINISHING TIME MINUS THE TIME REQUIRED TO COMPLETE THE ACTIVITY LATEST FINISH TIME: THE LATEST TIME AT WHICH THE ACTIVITY CAN BE COMPLETED WITH OUT DELAYING THE PROJECT
- 10. 10 SL.N O WORKS REQUIRED 1ST inspection after 8000 Hrs Period after 1st inspection 8000 Hrs 24000 Hrs 48000 Hrs 1 MEASUREMENT OF INSULATION RESISTANCE OF STATOR WINDING. X X X X 2 CHECK I.R & CONTINUITY OF RTD’s X X X 3 HYDRAULIC TEST OF STATOR WINDING. X X X 4 GAS TIGHTNESS TEST OF GENERATOR WITH PIPING SYSTEM X X X X 5 DISMANTLING OF TERMINAL BUSHING AND CHANGE OF GASKETS X 6 CHANGE THE GASKETS OF GAS COOLER X X 7 DISMANTLING OF END SHIELD & REPLACEMENT OF GASKETS X X X 8 CHECKING OF TIGHTNESS OF SLOT WEDGES X X X 9 CHECKING THE FIXING OF WINDING IN SLOT AND OVERHANG X X X 10 CHECKING CONDITION OF STATOR CORE X X X 11 ELCID/CORE LOSS TEST X X 12 CHECKING CONDITION OF TEFLON TUBE CONNECTION, WATER HEADER X X X TIME SCHEDULE
- 12. 12 POLISHING OF SLIPRING HYDROGEN GAS SHOULD BE PURGED OUT POLISHING OF SLIPRING IS CARRIED OUT BEFORE SHAFT COMING TO REST AFTER COOLING. SPECIAL TYPE MINI LATHE SHOULD BE ALIGNED DEPTH FEED : 0.1 to 0.15 mm FOR CUTTING 0.01 to 0.02 FOR GRINDING LONGITUDINAL FEED: 0.1 to 0.15 mm/rev FOR CUTTING 0.5 TO 0.6 mm / rev. for GRINDING FINISH SHOULD BE DELTA 6
- 13. 13 GROOVE CUTTING OF THE SLIPRING HELICAL GROOVES ARE PROVIDED FOR BETTER COOLING NORMAL GROOVE DEPTH : 6 mm IF THE GROOVE DEPTH BECOMES LESS THAN 2 mm GROOVE CUTTING IS NECESSARY TO BE CARRIED OUT AT LOWER SPEED OF THE SHAFT
- 17. 17 ROTOR THREADING IN 1 1. PLACE THE CARD BOARD AND THEN THE METAL PLATE INTO THE STATOR 2. INSTALL THE RAILS AND MOUNT THE LOWER PORTION OF THE OUTER TROLLEY ON THE RAILS 3. CONNECT THE EXTENSION PIPE TO THE HALF COUPLING OF THE ROTOR AND INNER TROLLEY ON THE SHAFT JOURNAL ON THE TURBINE SIDE. 4. REMOVE THE FAN BLADES 5. ASSEMBLE THE WOODEN BARRELS ON THE ROTOR BARREL WHERE THE ROTOR MEETS THE LIFTING SLINGS ARE POSITIONED. 6. ASSEMBLE THE TOP PORTION OF THE OUTER TROLLEY. 7. LIFT THE ROTOR BY CRANE.CHECK THE ROTOR IS HORIZONTAL. INSERT THE ROTOR CAREFULLY INTO THE STATOR TILL THE SLINGS PERMIT. OUTER TROLLEY TOP RAILS SLING EXTENSION PIPE METAL PLATE CARD BOARD INNER TROLLEY OUTER TROLLEY BOTTOM
- 18. 18 ROTOR THREADING IN 2 1. BRING THE LOWER PORTION OF THE TROLLEY UNDER THE TOP TROLLEY AND JOIN THEM BY BOLTS 2. LOWER THE ROTOR AND PLACE ON THE TROLLEYS 3. REMOVE THE SLINGS 4. PLACE THE “ I” BEAM ON THE TURBINE SIDE I BEAM
- 19. 19 ROTOR THREADING IN 3 1. PUSH THE ROTOR SLOWLY AND CAREFULLY INTO THE STATOR (CROWBARS ARE INSERTED INTO THE ROLLERS ON THE OUTER TROLLEY). 2. INSERT THE ROTOR TILL IT OCCUPIES A POSITION WHERE IT IS POSSIBLE TO PASS THE SLING UNDER THE PROJECTING PART OF THE EXTENSION PIPE , AND PUT THE SLING UNDER IT. SLING 3. LIFT THE ROTOR BY CRANE TILL THERE IS NO CONTACT ON THE INNER TROLLEY WITH THE SHEET
- 20. 20 ROTOR THREADING IN 4 1. BRING THE ROTOR TO THE POSITION AS SHOWN IN THE FIGURE 2. MAKE THE ROTOR REST ON THE BEAM TAKING CARE SO THAT IT DOES NOT REST ON THE STATOR 3. DISCONNECT THE EXTENSION PIPE 4. PASS THE SLING UNDER THE HALF COUPLING 5. LIFT THE END OF THE ROTOR 6. MOVE THE ROTOR TO A POSITION WHERE IT IS CONVENIENT TO REMOVE THE INNER TROLLEY 7. REMOVE THE INNER TROLLEY
- 21. 21 ROTOR THREADING IN 5 1. BY MEANS OF CROWBAR AND CRANE TAKE THE ROTOR TO THE POSITION WHERE HALF COUPLING OF TURBINE AND GENERATOR MEET 2. MOUNT THE LOWER HALF OF THE BEARING ON THE TURBINE SIDE 3. LOWER THE ROTOR ON THE BEARING 4. REMOVE THE I BEAM LP TURBINE LOWER HALF OF THE TE BEARING
- 22. 22 ROTOR THREADING IN 6 1. PLACE THE” I” BEAM ON THE EXCITER SIDE 2. REMOVE THE LOWER PART OF THE OUTER TROLLEY BY LIFTING THE ROTOR WITH CRANE 3. MAKE THE ROTOR REST ON THE “ I “ BEAM 4. REMOVE THE OUTER TROLLEY BOTH (TOP AND LOWER) 5. REMOVE THE RAILS 6. MOUNT THE EXCITER END BEARING PEDESTAL AND MOUNT THE LOWER HALF OF THE BEARING 7. LIFT THE END OF THE ROTOR BY CRANE 8. REMOVE THE “ I” BEAM 9. MAKE THE ROTOR REST ON THE BOTTOM HALF OF THE BEARING I BEAM
- 23. 23 GENERATOR PARTS FAN SHIELD FAN BLADE H2 SIDE DRAIN AIR SIDE DRAIN SEAL RING LABRINYTH STRIP SEAL OIL INLET SEALING COVER OIL DEFLECTOR PLATE SEAL BODY H2 SIDE OIL CATCHER SEALING CORD AIR SIDE OIL CATCHER END SHIELD
- 24. 24 SEAL RING & OIL CATCHER POSITION NOMINAL VALUE IN mm TOP 0.3. – 0.6 1 SIDE 0.17 – 0.35 BOTTOM 0.04 – 0.10 TOP 0.3. – 0.6 2 SIDE 0.17 – 0.35 BOTTOM 0.05 – 0.10 TOP 0.3. – 0.6 3 SIDE 0.17 – 0.35 BOTTOM 0.05 – 0.10 TOP 0.3. – 0.6 5 RADIAL 0.13-0.15 AXIAL CLEARANCE OF THE SLIP RING : 0.17 - 0.22 mm RADIAL CLEARAQNCES : 0.26 - 0.30 mm NOMINAL CLEARANCES OIL DEFLECTING RING END SHIELD H2 SIDE OIL CATCHER AIR SIDE OIL CATCHER SEALING COVER SEAL BODY
- 25. 25 6TH BEARING CLEARANCES BEARING YOKE 0.04 TO 0.17 BEARING OIL DEFLECTING RING OF BEARING OUTER BEARING OUTER OIL CATCHER U L S U S L 0.35 TO 0.45 0.25 TO 0.35 0.15 TO 0.25 INNER ODR OUTER ODR BEARING OUTER OIL CATCHER 0.4 TO 0.5 0.3 TO 0.45 0.15 TO 0.25 0.7 TO 0.9 0.35 TO 0.45 0 0.2 TO 0.4 0.15 TO 0.30 0.10 TO 0.20
- 26. 26 WINDING ON TE
- 27. 27 SEAL BODY
- 31. 31 GENERATOR ALIGNMENT H1 H2 L1 L2 r a FOR AXIAL ALIGNMENT H1/a = L1/r ∴ H1=(L1/r ) X a H2/a = L2/r ∴ H2=(L2/r ) X a FOR RADIAL ADJUSTMENT CORRECTION=ERROR/2 FOR AXIAL ADJUSTMENT TURBINE SHAFT AXIS TURBINE END BEARING EXCITER END BEARING RADIAL AXIAL
- 32. 32 COUPLING RUN OUT AND NATURAL RUN OUT RUNOUT CHECK OF GENERATOR ROTOR RADIAL RUNOUT SHOULD NOT EXCEED 0.03MM END FACE RUNOUT SHOULD NOT EXCEED 0.03MM LP TURBINE HALF COUPLING 5TH BEARING SHAFT JOURNAL 6TH BEARING SHAFT JOURNAL SLIPRINGS
- 33. 33 GENERATOR AIR GAP AIR GAP : 70 2.5% ( 1.75MM) CENTERING OF STATOR WITH RESPECT TO ROTOR SHOULD NOT DIFFER BY 0.5MM IN ALL FOUR DIRECTIONS 475 MM DIA 475 MM DIA
- 34. 34 MAGNETIC OFF CENTRE CENTERING OF STATOR FRAME WITH RESPECT TO ROTOR SHOULD NOT DIFFER BY 0.5MM IN ALL FOUR DIRECTIONS EXCITER ENDTURBINE END OFFSET OF STATOR AND ROTOR AXIX(VERTICAL) = 18MM IS ONLY FOR REFERENCE
- 35. 35 FAN BLADE CLEARANCES (EE)A > 40mm (EE) A < 10mm(TE) B = 2 mm to 2.98mm A B C D THE DIFFERENCE BETWEEN “A” AND “ B” AND “C” AND “D” SHOULD NOT EXCEED 0.7MM FAN BLADE FAN SHIELD ROTOR
- 36. 36 INSPECTION OF THE STATOR INSPECT THE WINDING FOR ANY BLOCK SPOT AND PRESENCE OF ANY OIL, CARBON DISCHARGES INSPECT THE CORE FOR ANY LOOSENESS, VENTILATION CANALS, AND HOTSPOT AND FUSION MARKS CHECK THE TEFLON TUBE FOR ANY DECOLORATION, CONDITIONS OF RUBBER GROMETS INSPECT THE OVERHANG WINDING SUPPORTS, SPACERS, CORE PRESS RINGS, CORE BOLTS AND ALL THE BOLTS AND NUTS OF THE SUPPORTS CHECK THE TERMINAL BUSHINGS, STATORWATER BUSHINGS AND GASKETS.
- 37. 37 DRYING OF STATOR WINDING BEFORE ANY ELECTRICAL TESTING WINDING SHOULD BE DRY. THE WINDING IS CONSIDERED TO BE DRY IF THE IR, PI VALUES ARE NORMAL THE STAGNATED WATER IF PUFFED OUT BY PASSING COMPLETELY DRY AND PURE AIR. THE OTHER METHODS IN AN EXTREME CASES ARE BY PASSING HOT AIR OR STEAM WINDAGE LOSS METHOD BY RUNNING THE MACHINE AT NO LOAD WITH AIR CORE LOSS METHOD BY MAGNETIC FLUX CREATED BY MAGNETISING THE COIL WOUND THROUGH STATOR BORE BY THREE PHASE SHORT CIRCUIT BY PASSING DC CURRENT IN TS-II / NLC WINDING IS DRIED COMPLETELY BY PASSING DEHUMIDIFIED HOT AIR AND THE RESULTS IS FAST AND EXCELLENT.
- 38. 38 INSULATION RESISTANCE OF STATOR PRECAUTIONS 1. WINDING SHOULD BE COMPLETELY DRY 2. NEUTRAL AND PHASE POINT SHOULD BE DISCONNECTED AND EACH WINDING SHOULD BE SEPARATE 3. WHILE MEGGERING ONE PHASE OTHER TWO PHASE SHOULD BE GROUNDED. ABSORPTION COEFFICIENT = R60 / R15 > 1.3 POLARISATION INDEX (PI) = R600 / R60 > 2 NOTE: THE RATIO IS BEING TAKEN TO AS MEANS FOR TEMPERATURE CORRECTION
- 39. 39 CURRENT COMPONENTS Ic- CAPACITANCE CURRENT 5KVDC Ic IpIr Ip – POLARISATION CURRENT DECAY WITH TIME Ir - LEAKAGE CURRENT CONSTANT AND MAINLY DEPENDS UPON THE DRYNESS OF THE WINDING THREE COMPONENTS OF CURRENT WHILE MEGGERING
- 40. 40 DC WINDING RESISTANCE V THE VALUES ARE COMPARED WITH FACTORY VALUE AFTER THE TEMPERATURE CORRECTION OF THE READING. THE VARIATION WITHIN 2% IS CONSIDERED AS NORMAL. V I I CONSTANT CURRENT GENERATOR WINDING
- 41. 41 HIGH VOLTAGE TEST PRECAUTIONS: 1. WINDING SHOULD BE COMPLETELY DRY. IR VALUE OF THE WINDING SHOULD BE SATISFACTORY. 2. NEUTRAL AND PHASE POINT SHOULD BE DISCONNECTED AND EACH WINDING SHOULD BE SEPARATE 3. WHILE MEGGERING ONE PHASE OTHER TWO PHASE SHOULD BE GROUNDED. 4. PERSONS SHOULD NOT BE ALLOWED NEAR THE WINDING TEST: 1. 2 TIMES THE RATED VOLTAGE +1 KV FOR FIRST TIME 2. 80% OF THE PREVIOUS VALUE FOR THE SECOND TIME 3. 80% OF THE PREVIOUS VALUE FOR THE SUBSEQUENT TIMES FOR OLD GENERATOR STATOR . 1. NOT USUALLY CARRIED BECAUSE OF DESTRUCTIVE NATURE OF THE TEST. 2. ONLY CARRIED OUT IN CASE OF ANY WORK IS CARRIED OUT IN THE GENERATOR STATOR. 3. THE VOLTAGE LEVEL FOR THE TEST DEPENDS ON THE AGE OF THE MACHINE.
- 42. 42 TAN MEASUREMENT IC CP IR RP E IR IC IT VOLTAGE E-TEST VOLTAGE IN STEPS OF 2 KV UPTO 10 KV IT- TOTAL CURRENT IR- RESISTANCE CURRENT CP- EQUIVALENT PARALLEL CAPACITANCE RP- EQUIVALENT PARALLEL RESISTANCE IT
- 43. 43 PARTIAL DISCHARGE TEST-1 PRINCIPLES • PARTIAL DISCHARGES ARE ELECTRICAL SPARKS WHICH OCCURS IN GAS VOIDS WITHIN THE INSULATION • DISCHARGES ARE PARTIAL AS SOME MORE INSULATION IS REMAINING TO PREVENT COMPLETE BREAK DOWN • IF PD CAUSE THE PD CHANNELS TO PROPOGATE WHICH RESULTS IN COMPLETE BREAK DOWN OF INSULATION • ELECTROMAGNETIC PROBES (PROXIMITY DETECTOR ) THAT IS SENSITIVE TO RADIO FREQUENCY SIGNALS PRODUCED BY PARTIAL DISCHARGES LOCATE SPECIFIC SITES OF DETERIORATION WITHIN THE WINDING TEST PROCEDURE • MACHINE SHOULD BE DISASSEMBLED • WITH NORMAL GROUND TO LINE VOLTAGE THE WINDING IS ENERGIZED. • ONE PHASE IS ENERGIZED WHILE THE OTHER TWO PHASES ARE GROUNDED. • THE PROBE IS POSITIONED NEAR STATOR COIL WEDGE AND SLOT EXIT ABOUT 100MM FROM THE WEDGE. • READING ARE TAKEN WITH PEAK PULSE METER.
- 44. 44 PARTIAL DISCHARGE TEST-2 PARTIAL DISCHARGE ARE HIGH FREQUENCY ELECTRICAL PULSE DUE TO DISCHARGE IN VOIDS IN THE INSULATION CORE CONDUCTOR VOIDS NEAR COPPER- NEGATIVE DISCHARGE VOIDS INSIDE THE INSULATION – BOTH POSITIVE AND NEGATIVE DISCHARGES VOIDS NEAR THE CORE – POSITIVE DISCHARGE IT PARTIALLY BRIDGES THE GAP BETWEEN THE INSULATION AND THE GROUND RATED VOLTAGE IS APPLIED IN THE WINDING AND WAVE FORMS ARE RECORDED. CRACKS / CONTAMINATIONS ON THE SURFACE OF THE INSULATION CAUSES PD
- 45. 45 ABOUT STATOR CORE • THE GENERATOR STATOR CORE IS BUILT FROM THOUSANDS OF THIN SHEET STEEL LAMINATION.(0.5mm) • THESE LAMINATIONS ARE COATED WITH A THIN LAYER OF VARNISH FOR PREVENTION OF CIRCULATING INDUCED CURRENTS ALSO KNOWN AS EDDY CURRENTS. • ANY DEFECT IN THE INTER LAMINAR INSULATION CAUSES FAULT CURRENT TO FLOW LOCALLY IN THE CORE. • THESE CIRCULATING CURRENT CAN THUS CAUSE LOCALISED OVER HEATING AND HOT SPOTS IN THE DAMAGED AREAS AND THIS MAY FURTHER DAMAGE THE CORE. • HENCE IT CALLS FOR TESTING THE INTERLAMINAR INSULATION
- 46. 46 CORE LOOP TEST A V AC VOLTAGE SOURCE FLUX DENSITY :14000/10000GAUSS VOLTAGE/CURRENT IN MAGNETISING WINDING 475V/970A 1.STATOR SHOULD BE SOLIDLY EARTHED.2.NO BODY SHOULD ENTER UNLESS SUPPLY IS SWITCHED OFF 3. CABLE SHOULD NOT BE IN DAMAGED CONDITION 4. THERE SHOULD NOT BE ANY MAGNETIC /METAL OBJECTS NEAR THE CASING 5. TEMPERATURE MONITORING SYSTEM SHOULD BE READY. STATOR STATOR
- 47. 47 DRAWBACKS OF RING LOOP TEST • IT IS A DESTRUCTIVE TEST • INVOLVES HEAVY POWER LOSS
- 48. 48 ELCID TEST-NEED • THE DIGITAL ELCID TEST USES 4% OF THE RATED FLUX LEVEL TO GENERATE FAULT LEVEL WITH IN THE CORE BODY.
- 49. 49 PRINCIPLE OF ELCID TEST • THE CIRCUMFERENTIAL MAGNETIC FIELD OF THE CORE IS DUE TO THE EXCITATION PLUS THAT DUE TO ANY FAULT CURRENTS PRESENT. • THE EFFECT OF THE MAGNETIC FIELDS IS TO PRODUCE MAGNETIC POTENTIAL GRADIENT ON THE CORE SURFACE. • THIS MAGNETIC POTENTIAL GRADIENT IS DETECTED BY SPECIALLY WOUND COIL KNOWN AS CHATTOCK COIL • THIS COIL PROVIDES AN OUTPUT PROPORTIONAL TO THE DIFFERENCE IN THE MAGNETIC POTENTIAL BETWEEN ITS TWO ENDS. • A SENSING HEAD (CHATTOCK COIL) IS PASSED OVER THE SURFACE OF THE CORE TO DETECT MAGNETICALLY THE PRESENCE OF FAULT
- 50. 50 ELCID TEST
- 51. 51 ELCID TEST –HOW RECORDED THE SIGNAL PROCESSOR IS CALIBRATED TO GIVE A DIRECT READING OF THE VALUE OF 1. DISTANCE INFORMATION ON THE X AXIS 2. THE FAULT CURRENT ALONG Y AXIS.
- 53. 53 ELCID TEST CALCULATION Vt = (.04 X Vp-p )/ (2 x √3 x k x TP) Vt = TEST VOLTAGE MEASURED IN THE TRACE WINDING Vp-p = RATED PHASE TO PHASE VOLTAGE K = PITCH FACTOR (0.92 FOR ALL GENERATORS) TP = TURNS IN SERIES /PHASE
- 54. 54 STATOR SLOT STATOR SLOT SLOT WEDGE SLOT RIPPLE SPRING GLASS TEXTOLITE SPACERS SOILID CONDUCTOR HOLLOW CONDUCTOR TOP BAR INSULATING PACKING BOTTOM BAR THERMOREACTIVE INSULATION BOTTOM PACKING
- 55. 55 STATOR WEDGE DEFLECTION THE WINDINGS ARE SUBJECTED TO EXPANSION, CONTRACTION AND VIBRATIONS WHICH LEAD TO LOOSENING OF WEDGE THE TIGHTNESS OF THE WEDGES IS CHECKED BY KNOCKING WITH A SMALL HAMMER. FROM THE KNOCKING SOUND THE LOOSENESS OF THE WEDGE IS JUDGED. IF TOP RIPPLE SPRINGS ARE PROVIDED, THEN KNOCKING METHOD CAN NOT BE USED. DEFLECTION OF WEDGE IS MEASURED BY APPLYING CALCULATED PRESSURE USING “WEDGE DEFLECTION CHECKING KIT” TOP RIPPLE SPRINGS ARE NOT PROVIDED IN THE END WEDGES AND WHERE RTDs ARE PROVIDED. DEFLECTION OF LESS THAN 0.9 mm IS ALLOWED FOR 60% OF THE WEDGES AND A DEFLECTION OF LESS THAN 1.1 mm IS ALLOWED FOR 40% OF THE WEDGES. THE PRESSURE APPLIED IS CALCULATED USING THE FORMULA REQUIRED MANOMETER PR. = ((10 X PF ) / FK ) X LN X BN BAR SPECIFIC TEST PRESSURE FOR THE WEDGES (PF ) = 1.8 N / mm2 LN = SLOT WEDGE LENGTH IN cm BN = SLOT WIDTH IN cm PF= SPECIFIC TEST Pr. IN N/mm2 FK= PISTON SURFACE AREA IN cm2
- 56. 56 WEDGE DEFLECTION LIMITS 1. IF THE WEDGE MOVEMENT OF MORE THAN 1.1MM IS MEASURED IN ANY SLOT, THE NUMBER OF MEASURING POINTS IN THIS SLOT IS DOUBLED AND IF THE VALUE IS EXCEEDED IN 2 POINTS. 2. ALL THE WEDGES IN THIS SLOT SHOULD BE CHECKED TO KNOW THAT NOT MORE THAN 2 POINTS ARE HAVING MOVEMENT MORE THAN THE SPECIFIED VALUE. 3. IF THE VALUE IS EXCEEDED, CORRECT PACKER ARE INSERTED AND TIGHTENED. 4. AFTER ALL SUCH WEDGES ARE TIGHTENED, THE WEDGE TIGHTNESS CHECKING WILL BE CARRIED OUT AGAIN. 5. AFTER TIGHTENING SLOT WEDGES, DEFLECTION SHOULD BE: BETWEEN 0.1mm to 0.3 mm FOR 75% : NOT MORE THAN 0.45 mm FOR 25%
- 57. 57 INSPECTION OF ROTOR INSPECT THE JOURNAL FOR ANY PITTING AND SCRATCHES INSPECT FOR ANY DUST OR ANY UNDESIRABLE MATERIALS LYING IN VENTILATION HOLES AND VENTILATION CANALS OF RETAINING RING CHECK THE LOCKING OF BALANCE WEIGHTS CHECK THE TIGHTNESS OF WEDGES AND PACKERS UNDER RETAINING RING DP TEST OF FAN BLADES AND RETAINING RING DO NOT REST THE ROTOR ON RETAINING RING,SLIPRINGS,HALF COUPLING AND ROTOR WEDGES PRESERVE AGAINST RUSTING OF JOURNAL, SLIP RING AND HALF COUPLING WHEN THE ROTOR IS OUT.
- 58. 58 TESTS ON ROTOR INSULATION RESISTANCE VALUE USING 500 V MEGGER. IT SHOULD BE MORE THAN 1. 3 MEGA OHMS DC RESISTANCE VALUE IS MEASURED. AFTER TEMPERATURE CORRECTION, IT IS COMPARED WITH FACTORY VALUE. VARIATION WITH IN 2 % IS CONSIDERED AS NORMAL AC IMPEDANCE VALUE IS MEASURED AT VARIOUS SPEED OF THE ROTOR. HV TEST: AT 2.5 KV, FOR ONE MINUTE FOR A NEW ROTOR AT SITE. VALUE MAY BE REDUCED FOR OLD ROTOR. GENERALLY CARRIED OUT ONLY WHEN ANY REPAIR IS DONE ON THE ROTOR WINDING.
- 60. 60 RECURRENT SURGE OSCILLOSCOPE TEST ON ROTOR A D.C STEP BETWEEN ONE END OF THE ROTOR WINDING AND THE ROTOR BODY. THE TRANSMITTED WAVE AND THE REFLECTED WAVE AT THE INPUT END OF THE WINDING IS MONITORED USING TWO OSCILLOSCOPE CHANNELS IF THE VOLTAGE STEP IS APPLIED FROM EACH END OF THE ROTOR WINDING THEN ALTERNATIVELY THEN TWO OSCILLOSCOPE TRACES WILL BE OBTAINED WHICH MAY BE SUPERIMPOSED ON THE OSCILLOSCOPE SCREEN A HEALTHY ROTOR WILL HAVE TWO INDENTICAL TRACES A ROTOR WILL A FAULT WILL HAVE DIFFERING TRACES THE POSITION OF THE FAULT MAY BE DEDUCED BY SCALING THE TIME DOMAIN
- 61. 61 RSO TEST CIRCUIT CONNECTION Pulse Generator oscilloscope chanell 1
- 62. 62 ROTOR GAS TIGHTNESS TEST GENERATOR STATOR FAN BLADE INNER CURRENT CARRYING BOLT CORE BAR ROTOR RETAINING RINGHALF COUPLING OUTER CURRENT CARRYING BOLT SLIP RING NITROGEN CYLINDER GAS TIGHTNESS OF ROTOR PRESSURE REGULATOR
- 63. 63 ROTOR SLOT SLOT WEDGE TOP LINER ROTOR SHAFT SLOT BACK BOTTOM LINER
- 64. 64 PURGE TEST -2
- 65. 65 PURGE TEST-3
- 66. 66 STATIC PRESSURE AND VELOCITY PRESSURE STATIC PRESSURE:THE RISE IN STATIC PRESSURE AT A POINT MINUS THE REFERENCE ATMOSPHERIC PRESSURE. VELOCITY PRESSURE: THE RISE IN STATIC PRESSURE WHICH OCCURS WHEN AIR MOVING WITH SPECIFIED VELOCITY AT A POINT IS BROUGHT TO REST WITH OUT LOSS OF MECHANICAL ENERGY
- 67. 67 PURGE TEST 1 PRESSURE OF 3. 0 ± 0.1KG/cm2 GAUGE SHOULD BE APPLIED AT THE VENTILATING CANALS OF SLOT THROUGH THE ADOPTER. 2. WHILE CARRYING OUT TEST ON OVERHANG, A STATIC PRESSURE OF 50 mm OF WATER COLUMN SHOULD BE MAINTAINED UNDER RETAINING RING. 3. THE AVERAGE VELOCITY PRESSURE IN THE CANALS OF SLOT PORTION SHOULD NOT BE LESS THAN 15 mm OF WATER COLUMN FOR EACH ZONE AND 21 mm OF WATER COLUMN FOR EACH SLOT. 4. THE MINIMUM VALUE OF STATIC PRESSURE IN INDIVIDUAL CANALS OF OVER HANG PORTION SHOULD NOT BE LESS THAN 15mm OF WATER COLUMN. 5. FULLY CLOSED CANALS ARE NOT ALLOWED IN THE OVER HANG PORTION OF ROTOR WINDING. 6. ENSURE THAT ALL THE VENTILATION CANALS/ DUCTS ARE PROPERLY SEALED AFTER THE PURGE TEST.
- 68. 68 HYDRO TEST OF STATOR WINDING HYDRAULIC TEST FOR THE STATOR WINDING IS CONDUCTED AT 5 KG/ cm2 FOR 24 HOURS USING FILTERED DM WATER. NO DROP IS ALLOWED. PROBABLE LEAK POINTS ARE TEFLON HOSES AT THE TURBINE END THE CONNECTING PIPES OF THE TERMINAL BUSHINGS THE CONNECTING PIPES AT THE EXCITER END
- 69. 69 EPOXY GLUE INJECTION OF STATOR OVERHANG WINDING & VARNISHING OF STATOR THE STATOR OVERHANG WINDING ARE SUBJECTED TO MORE STRESS DURING ANY ELECTRICAL FAULT TO GIVE ADDITIONAL STRENGTH TO THE OVERHANG WINDING SUPPORTS, EPOXY GLUE IS PUMPED & SPRAYED OVER IT AFTER CLEANING AND DRYING BY EXTERNAL HEATING, USING ELECTRICAL BULBS. RESIN CY 205 : ( 4250 GRAMS) DILUENT – C : (750 GRAMS) HARDENER- HY 840 : (2000 GRAMS) THE CORE IS GIVEN A COATING OF VARNISH AFTER CLEANING AND DRYING.
- 70. 70 AIR TIGHTNESS TEST OF GENERATOR So – LEAKAGE OF GAS ( AT ATM. PRESSURE AND AT 20 OC IN %) P1 & P2 - ABS. PR. AT BEGINNING AND END OF THE TEST IN mm of HG. T1 & T2 ABS. TEMP AT BEGINNING AND END OF THE TEST IN DEGREE KELVIN. t – DURATION OF TIME. AFTER COMPLETING THE ASSEMBLY & COMMISSIONING OF SEAL OIL SYSTEM, AIR LEAK IS CONDUCTED WITH DRY AIR, AT A PRESSURE OF 4 KSC FOR 24 HOURS % 925 : 2 2 1 1 T P T P t So Vo = So X V V – GAS VOLUME OF STATOR IN M3 ( 56 M3 ) Vo – ABSOLUTE IN LEAKAGE IN M3100
- 71. 71 AIR TIGHTNESS TEST -2 VOLUME IS INVERSELY PROPORTIONAL TO SQUARE OF DENSITIES. 3.20.1138/1.18 AirV HydrogenV o o GAS LEAK SHOULD BE WITHIN 1 % OF THE VOLUME
- 72. 72 BRUSHGEAR CLEARANCES I1 I2 I1 & I2 = 0.1 TO 0.3 S = 2 TO 2.5 S t1 t2 t4 t3 t1, t2 , t3, t4 = 3.4 to 4.1 BRUSHGEAR BRUSH HOLDER SLIPRING ALIGNMENT OF BRUSHGEAR BRUSH HOLDER AND BRUSHES BRUSH BRUSH HOLDER
- 73. 73 STAGGERING OF BRUSHES A D BC A 0 D 50 TO 54 B 16- 20 C 32 TO 36
- 74. 74 THANK YOU