Preventive maintenance checklist for transformer

Transformer is a costly device as well as it supplies power to a large area. Its breakdown may cause interruption of power for long period and causes loss of revenue to loss of production or run of DG sets. Hence, it is better to do preventive maintenance of transformer regularly.

Here is a list of preventive maintenance of transformer and preventive maintenance schedule.

Hourly check and Record keeping – A Check of Transformer

  1. Oil temperature
  2. Winding temperature
  3. Ambient temperature
  4. Load in amps
  5. Voltage incoming and outgoing
  6. Check for load balancing in all three phases

Daily check and Record keeping – B Check of Transformer

  1. Cleanliness of the transformer
  2. Check for any leakage of the oil through the transformer
  3. Tap position
  4. Terminal sounds
  5. Humming sound
  6. Body Earthing
  7. Oil level in the transformer (if it is low, you should add in more oil and also discover whether there is a leak)
  8. Oil level in the bushing
  9. Oil level in the OLTC conservator (either a gauge or sight window will show you the level. If it is low, simply top it up with new oil).
  10. Dehydrating breather ( must check both that the air passages are free and the color of the active agent. Pink means the charge needs to be changed)
  11. Relief diaphragm
  12. Cooling fan
  13. Bearing motor (lubricates it and check the contacts. If the contacts have worn, they should be replaced)
  14. Operating mechanism

Quarterly check and Record keeping – C Check of Transformer

  1. Cleaning of bushing and check for cracks in the bushing and replace if any cracks
  2. Cleaning of the external surface of the tank
  3. Check the oil level in the conservator tank and oil gauge
  4. Quality of oil ( Dielectric Strength) by Sample test
  5. Check the condition of the silica gel, change if required (Blue is good and Pink is bad and need to change)
  6. Check vent pipes for cracks and leakage
  7. Check for loose connection
  8. Check for oil leakage

Yearly check and Record keeping – D Check of Transformer

  1. Testing BDV ( Break Down Voltage ) and acidity in the oil.
  2. Oil filtration if required.
  3. Measurement of earth resistance
  4. Check for earthing of the transformer
  5. Check the Buchholtz relay for gas collection and ensure their proper working.
  6. Oil in the transformer (this time check the acidity resistivity, tan delta and sludge. It may need to be filtered or replaced entirely)
  7. Oil-filled condenser bushing
  8. Gasket joints (may need to be tightened to avoid uneven pressure)
  9. Cable boxes
  10. Relays alarm and other circuits
  11. Painting