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Maintenance philosophy of POWERGRID

Maintenance philosophy of POWERGRID. INTRODUCTION:. In today’s scenario of power deficit, the availability of a transmission line is very critical as outage of one line results in loading restriction on other parallel lines also. The equipments are vital elements of any

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Maintenance philosophy of POWERGRID

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  1. Maintenance philosophy of POWERGRID INTRODUCTION: In today’s scenario of power deficit, the availability of a transmission line is very critical as outage of one line results in loading restriction on other parallel lines also The equipments are vital elements of any transmission system. It is our experience that less attention is being given to preventive maintenance of Equipments and protection systems. The equipments, if not properly maintained, are more susceptible to failures as compared to transmission lines and non operation of protection systems.

  2. The failure of sub station equipment can cause consequential damage to other equipments also. Recent example is failure of one 400 KV circuit breaker at MSEB Chandrapur with not operation of protection System had caused collapse of Western Maharashtra grid. The down time of a system, due to failure of equipment, is quite high. IN VIEW OF ABOVE, PRIME IMPORTANCE IS GIVEN TO PREVENTIVE MAINTENANCE OF EQUIPMENTS, PROTECTION SYSTEM AND TRANSMISSION LINES IN POWERGRID

  3. Maintenance schedule has been prepared for each and every equipment of sub station. This consists of Activities requiring shut down of equipments Activities which do not require shut down. Various activities are classified as per frequency of testing i.e. monthly, half yearly, yearly, two yearly, four yearly etc. The test results of various maintenance activities are recorded in a standard format to avoid any ambiguity in recording the results. This also improves the traceability of the test records for one particular equipment.

  4. Acceptable / permissible limits for various tests have been compiled in the form of a document. The permissible limits have been arrived at, as per the recommendation of various manufacturers and experience gathered by POWERGRID. The test results are analyzed, with reference to deviation from acceptable limits / last test results / commissioning results, after converting them on a common base. In case the result violates the prescribed norms, the tests are repeated before deciding about replacement. Replacement is planned in co-ordination with region. The approving authority for various tests has been identified in the document.

  5. Based on consumption pattern of various sub station equipments, norms have been prepared for keeping the spare quantities of various sub station equipment. The availability of these spares is monitored at Regional level. In case of any item falling short of norms, immediate action is taken for procurement To increase the confidence of working personnel, the P manuals have been developed for various equipments giving minute details of various parts. Documents detailing various testing procedures have been formulated.

  6. The failure of sub station equipment is analyzed to identify the reason of failure and arriving at remedial measures to avoid recurrence in future. These reports are approved by Director (O), POWERGRID. . The findings of such analysis are circulated up to sub station level for increasing awareness To monitor the maintenance checks for various equipments, audit of each sub station, once in two years, is carried out by Regional team and discrepancies noticed are complied with. Similarly once in 4 years, audit by corporate team is carried out.

  7. The condition of spare equipments available in the stores is monitored at regular interval. The procedure of storing spare equipments is documented. These documents are reviewed once in two years. The feedback is sought from various sites about periodicity of various tests / deletion of some tests / inclusion of new test. Various new tests, introduced recently, are also added depending upon their utility.

  8. A check list has been developed for higher authorities visiting the sub stations. This list includes various activities of sub station Subsequent to visit to a sub station by GM / ED, the check list is filled up and send to Corporate center.

  9. For monitoring the healthiness of various sub station equipments, following state of art tests have been introduced. • Third harmonic leakage current measurement for lightening arresters • Thermo vision scanning of sub station equipments • Capacitance and Tan delta measurement • for transformer / reactor bushing, winding, • grading capacitor, current transformer • and capacitive voltage transformer (CVT) • Dynamic contact resistance measurement • for circuit breakers • Battery impedance testing • Frequency response analysis for transformer • Dissolved gas analysis for transformer oil

  10. The main activities for various equipments are detailed below: TRANSFORMERS AND REACTORS * 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.

  11. A. SF6 CIRCUIT BREAKERS *At time of commissioning then after 6 months and one & half years of commissioning and thereafter once in every three years. HYERAULIC OPERATING MECHANISM II. PNEUMATIC OPERATING MECHANISM B. AIR BLAST CIRCUIT BREAKERS C.MOCBs

  12. * - For all HV/EHV Circuit Breakers only ** - For 400kV BHEL, CGL & ABB make CBs only E. MEASUREMENT/ TESTING * First time after one year from commissioning and then once in every four years

  13. 3.CURRENT TRANSFORMERS *- First time after one year from commissioning and then once in every two years. 4. CAPACITVE VOLTAGE TRANSFORMERS *First time after one year from commissioning and then once in every three years. For CVTs in which isolation of neutral of intermediate PT is not possible at site, this test is not required to be carried out. ** If secondary voltage violate norms, voltage measurement interval to be as per CVT replacement norms 5.SURGE ARRESTERS * Leakage current measurement to be carried out after annual maintenance

  14. 6. ISOLATORS AND EARTH SWITCHES MAIN CONTACTS EARTH SWTICH

  15. 7. WAVE TRAPS 8. AIR CONDITIONING PLANT 9. BATTERIES AND DC DISTRIBUTION SYSTEM

  16. 10. FIRE PROTECTION SYSTEM

  17. 15.PREVENTIVE MAINTENANCE SCHEDULE FOR DG SET

  18. THANK YOU

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