Presentation on theme: "Maintenance philosophy of POWERGRID"— Presentation transcript:
1 Maintenance philosophy of POWERGRID INTRODUCTION:In today’s scenario of power deficit,the availability of a transmission lineis very critical as outage of one line resultsin loading restriction on other parallel linesalsoThe equipments are vital elements of anytransmission system.It is our experience that less attention isbeing given to preventive maintenance ofEquipments and protection systems.The equipments, if not properly maintained,are more susceptible to failures as comparedto transmission lines and non operation ofprotection systems.
2 The failure of sub station equipment can cause consequential damage to otherequipments also. Recent example is failureof one 400 KV circuit breaker at MSEBChandrapur with not operation of protectionSystem had caused collapse of WesternMaharashtra grid.The down time of a system, due to failure ofequipment, is quite high.IN VIEW OF ABOVE, PRIME IMPORTANCEIS GIVEN TOPREVENTIVE MAINTENANCE OF EQUIPMENTS,PROTECTION SYSTEM AND TRANSMISSIONLINESINPOWERGRID
3 Maintenance schedule has been prepared for each and every equipment of sub station.This consists ofActivities requiring shut down of equipmentsActivities which do not require shut down.Various activities are classified as perfrequency of testing i.e. monthly, half yearly,yearly, two yearly, four yearly etc.The test results of various maintenanceactivities are recorded in a standard formatto avoid any ambiguity in recording theresults. This also improves the traceabilityof the test records for one particularequipment.
4 Acceptable / permissible limits for various tests have been compiled in the form of adocument.The permissible limits have been arrived at,as per the recommendation of variousmanufacturers and experience gathered byPOWERGRID.The test results are analyzed, with referenceto deviation from acceptable limits / last testresults / commissioning results,after converting them on a common base.In case the result violates the prescribednorms, the tests are repeated before decidingabout replacement.Replacement is planned in co-ordinationwith region.The approving authority for various tests hasbeen identified in the document.
5 Based on consumption pattern of various sub station equipments, norms have beenprepared for keeping the spare quantitiesof various sub station equipment.The availability of these spares is monitoredat Regional level.In case of any item falling short of norms,immediate action is taken for procurementTo increase the confidence of workingpersonnel, the P manuals have beendeveloped for various equipments givingminute details of various parts.Documents detailing various testingprocedures have been formulated.
6 The failure of sub station equipment is analyzed to identify the reason of failureand arriving at remedial measures to avoidrecurrence in future.These reports are approved by Director (O),POWERGRID..The findings of such analysis are circulatedup to sub station level for increasingawarenessTo monitor the maintenance checks forvarious equipments, audit of each substation, once in two years, is carried out byRegional team and discrepancies noticedare complied with.Similarly once in 4 years, audit by corporateteam is carried out.
7 The condition of spare equipments available in the stores is monitored at regular interval.The procedure of storing spare equipmentsis documented.These documents are reviewed once intwo years.The feedback is sought from various sites aboutperiodicity of various tests / deletion of sometests / inclusion of new test.Various new tests, introduced recently, arealso added depending upon their utility.
8 A check list has been developed for higher authorities visiting the sub stations. This listincludes various activities of sub stationSubsequent to visit to a sub station byGM / ED, the check list is filled up and sendto Corporate center.
9 CHECK LIST FOR INSPECTION BY HODs. Region:Substation/Transmission Line:Date of Visit:Control Room:1Healthiness of Event LoggerYES/NO2Healthiness of Disturbance Recorders.3Healthiness of Line Fault Locators.4All metering instruments are working.5All protections are in service.6All annunciation facia are working.7Healthiness of PLCC8Healthiness of communication9Proper maintenance of operation records.SwitchyardProper identification of phases.Equipment identification and numbering.Condition of equipment/painting etc.House keeping of switchyard.Proper earthing of equipment.
10 For monitoring the healthiness of various sub station equipments, following state ofart tests have been introduced.Third harmonic leakage currentmeasurement for lightening arrestersThermo vision scanning of sub stationequipmentsCapacitance and Tan delta measurementfor transformer / reactor bushing, winding,grading capacitor, current transformerand capacitive voltage transformer (CVT)Dynamic contact resistance measurementfor circuit breakersBattery impedance testingFrequency response analysis for transformerDissolved gas analysis for transformer oil
11 Activity Condition Period The main activities for various equipments are detailed below:TRANSFORMERS AND REACTORSActivityConditionPeriodTesting of oil for DGA and other oil parameters *W S/DHYVibration measurements (for Shunt Reactors only)2Y %Measurement of BDV of OLTC oilS/DYTan measurement for Bushings2Y $IR measurement of Windings(Polarization Index and D.A. Ratio)!4 Y **Tan measurement of Windings4 Y**Measurement of Windings resistance at all tap positionsFrequency Response AnalysisMaintenance of OLTC driving mechanismChecking of all remote indications(WTI and Tap position indicator)Electrical checking/testing of Pressure ReliefDevice,Buchholz relay, OLTC surge Relay andChecking /Replacement of the gaskets of terminal boxChecking/testing of Buchholz relay by oil drainingChecking and Cleaning of Diverter Contacts(50,000 operations)SOSChecking and calibration of OTI, WTI2YFiltration / Replacement of oil of OLTCFiltration/ Degassing of main tank oil* Water Content, BDV, Sp. Resistance, Tan, IFT, Total Acidity, 2-Furfuraldehyde etc.** First time after one year from commissioning and then once in every four years.% Vibration measurement, 3M and 6M after commissioning@ Base Signature before commissioning for all ICTs/Reactors$ Tan Delta measurement of Bushing within guarantee period after commissioning.! Di-electric Absorption Ratio To be measured as per the following combinations:N/E, N/LV and LV/E.
12 A. SF6 CIRCUIT BREAKERSActivityConditionPeriodDew Point measurement of SF6 gasS/D3Y**At time of commissioning then after 6 months and one & half years ofcommissioning and thereafter once in every three years.HYERAULIC OPERATING MECHANISMChecking of oil pressure drop during duty cycle operation checkS/DYChecking of auto-starting/stopping of oil pumpII. PNEUMATIC OPERATING MECHANISMFunctional checking of auto-starting of air compressors and dryersS/DYMaintenance of Air Dryer, if providedW/S/DHYChecking of air pressure drop during dutycycle operationB. AIR BLAST CIRCUIT BREAKERSDew Point Measurement of operating air at theoutlet of Air DrierW S/DYC. MOCBsTesting of oil for BDVW S/DY
13 D.BREAKER OPERATION CHECKS CB Operating Timings (Main, PIR, Aux.)S/DY *Static Contact Resistance2YDynamic Contact resistance(DCRM)Contact Travel,** Contact Speed,**Contact wipe, Arcing contact lengthChecking of Pole discrepancy relayYFunctional checks, duty cycleoperation including rapid re-closing(O-0.3s-CO)Checking of all operation lock-outsChecking of all interlocksChecking of pressure settings* For all HV/EHV Circuit Breakers only** - For 400kV BHEL, CGL & ABB make CBs onlyE. MEASUREMENT/ TESTINGChecking of close/trip coil currentsS/DYChecking of healthiness of OperationCounterCapacitance and tan measurement of grading capacitors4Y** First time after one year from commissioning and then once inevery four years
14 4. CAPACITVE VOLTAGE TRANSFORMERS 3.CURRENT TRANSFORMERSMeasurement of Tan and CapacitanceS/D2Y*DGA and testing of other parameters of oilSOSThermovision Scanning of CT and Top domeW S/DYChecking of Bellow ExpansionMN2 Pressure Checking2Y*- First time after one year from commissioning and then oncein every two years.4. CAPACITVE VOLTAGE TRANSFORMERSVisual checking of earthing HF point (in case it is not being used for PLCC)S/DYChecking for any breakage or cracks in cementing jointCapacitance and Tan measurement3Y *Measurement of voltage in S/Y MBW S/D6 M**Thermo vision Scanning of Capacitor stacks*First time after one year from commissioning and then once inevery three years. For CVTs in which isolation of neutral of intermediatePT is not possible at site, this test is not required to be carried out.** If secondary voltage violate norms, voltage measurement interval to beas per CVT replacement norms5.SURGE ARRESTERSChecking of leakage current *(Third Harmonic Resistive Current)W S/DYTesting of countersMeasurement of Capacitance and Tan and IR of each stackS/DSOS* Leakage current measurement to be carried out after annual maintenance
15 6. ISOLATORS AND EARTH SWITCHES MAINTENANCE OF OPERATING MECHANISMLinkages including transmission gearsS/DYStopper boltsCleaning of auxiliary switch contactsand greasing with silicon greaseLubrication of operating mechanism.Hinges, lock joints on levers, BearingsChecking of all mounting bolts for tightnessW S/DMAIN CONTACTSCleaning and lubrication of main contactsS/DYAlignmentMain contact resistance measurement4YTightness of Bolts, nuts and pins etc.Cleaning of support insulators and checking ofinsulator cracks, if anyChecking of InterlockEARTH SWTICHChecking & Alignment of earthing bladesS/DYCleaning of contactsContact resistance4YOperation of earthing switchChecking of Aluminum / Copper flexibleconductorChecking of earth connectionsof structure and MOM box
16 8. AIR CONDITIONING PLANT 7. WAVE TRAPSTightness & cleanlinessS/DYGeneral inspection / cleaning of tuning unit8. AIR CONDITIONING PLANTChecking of oil pressure switch. LP/HP, cutout switches, solenoid valve, thermostat, Humidistat etc.S/DYChecking Operation of Level switchHYChecking Water qualityW S/DCleaning of nozzles for cloggingQYLubrication of moving partsTerminal connection checkingCleaning of Bus Bars, Insulators etc.Tightness of the connectionsChecking of all interlocks9. BATTERIES AND DC DISTRIBUTION SYSTEMChecking control cards of charger& Measurement of test point voltage valuesS/DYBattery Impedance testingW S/DDischarge test of Battery Set3YChecking of any earth fault(If E/F relay not provided)MTesting of DC E/F and Under Voltage relays
17 10. FIRE PROTECTION SYSTEM Cleaning/Replacement of Air FilterWS/DMChecking of compressor oil and replaceif necessaryS/DQYMaintenance & cleaning of compressor valves, gaskets, valve plates and replace, if necessaryOperation check of low oil level switchCleaning and checking for seating of the breather valveCleaning of NRV/HP tankYGeneral overhaulSOSDetectorsW S/Di) Sequence test for annunciation inControl Room panelii) Smoke testiii) CleaningDIESEL ENGINEChecking/replacement of fuel oil filterLube oil filter, Air filterPump OverhaulingChecking of belt tightnessCleaning of oil strainerChecking of alignment of pump setOverhaulingChecking of pressure of the hydrant systemat the remotest end, auto-starting of pumps,diesel engine etc.Operation of Deluge system, check outletpressure check alarm, check starting ofDiesel/electrical pump.
18 15.PREVENTIVE MAINTENANCE SCHEDULE FOR DG SET Replacement of oil filter afterrecommended running hoursW S/DY/SOSCheck for fan hub, drive pulley and water pumpYReplacement of Air cleaning elementCheck for Governor linkages, fueltransfer pump, fuel line connectionsDrain Sediments from fuel tank, changefuel filter and clean fuel tank breatherStator winding IR measurementS/DChecking/Cleaning of Slip ring and its brushesTesting of protection/control relays andalarmsCheck for air leaks and exhaust Restrictions