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Power transformer maintenance schedule
- 1. MAINTENANCE INSTRUCTIONS FOR POWER TRANSFORMERS Maintenance Schedule Sl No Inspection frequency Items to be inspected To be checked Action required if inspection shows unsatisfactory conditions 1 Hourly Ambient temperature 2 Hourly Winding temperature Ensure that temperature rise is within specified limits. 3 Hourly Oil temperature 4 Hourly Load (amps) Check against rated figures given on the name plate 5 Hourly Voltage 6 Daily Oil level in transformer Check oil level gauge If low, top with dry oil find whether there is any leak. 7 Daily Oil level in bushing -- -- 8 Daily Dehydrating breather Check that air passages are free. Check colour of active agent If silicagel is pink, change by new charge. The old charge may be reactivated for using again. 9 Daily Oil level in OLTC conservator Check oil sight window or oil level gauge If low, top with new dry oil
- 2. Sl No Inspection frequency Items to be inspected To be checked Action required if inspection shows unsatisfactory conditions 10 Daily Relief diaphragm of OLTC explosion vent -- Replace if cracked or broken 11 Daily Cooler fan, bearing motor & operating mechanism Check the bearings. Examine contacts, check manual control and interlock Lubricate the bearing. Replace burnt or worn contacts. 12 Quarterly Bushings Examine for cracks and dirt deposit Clean the dirt. If cracked or broken replace the bushing. 13 Quarterly Oil in transformer Check for dielectric strength and water content Take suitable action to restore quality of oil. 14 Half yearly or at the end of 5000 operations Oil in the diverter switch of OLTC a. Dielectric strength Filter or replace if BDV is less than specified value. b. Water content Measure the water content using KARL FISHER method. Replace/ recondition if exceeds that limits specified 15 Yearly Oil in transformer Check acidity resistivity, tan delta and sludge Filter or replace 16 Yearly Oil filled condenser bushing Refer to the maintenance schedule for OIP condenser bushings As recommended 17 Yearly Gasket joints Tighten the bolts evenly to avoid uneven pressure
- 3. Sl No Inspection frequency Items to be inspected To be checked Action required if inspection shows unsatisfactory conditions 18 Yearly Cable boxes Check sealing arrangements and find out whether there is any leak Replace gasket if leaking 19 Yearly Relays alarm and other circuits Examine relay and alarm contacts, their operation fuses etc. check relay accuracy. Clean the components. Replace contacts and fuse if necessary 20 Yearly Painting Rusting/colour Touch up to be done 21 Yearly Earth resistance -- Take suitable action if earth resistance is high 22 After 50000 operations of the OLTC Arcing contacts -- Replace if necessary 23 -do- Lubricating oil in the gear box of driving mechanism Low oil level Add or replace with lubricating oil 24 5 yearly 1000 kVA to 2000 kVA Overall inspection including core and coil Wash the core and coils with clean oil 7 – 10 yearly above 3000 kVA Note : In case of abnormal phenomena occurring during service, inform the manufacturer the exact nature of the phenomena together with the name plate particulars for easy identification.