Transformer Maintenance Checklist



As with any equipment, transformers need to be maintained in order to keep running properly and to make sure that you get the full-service life possible out of them. Maintaining your transformers can be time-consuming, because there are items that need to be frequently checked and others that need to be inspected weekly, monthly, semi-annually and annually. At VCM Solutions, we can perform this maintenance for you. However, if you’re not working with us, or are just curious about what it takes to maintain transformers, here is a preventive maintenance checklist you can use. 

Transformer Maintenance Checklist 

Items that need to be inspected hourly: 

  1. Winding temperature 
  2. Ambient temperature 
  3. Oil temperature (unless it’s a dry-type transformer, then see below) 
  4. Load in amps 
  5. Voltage 

Items that need to be inspected daily: 

  1. Oil level in the transformer (if it is low, you should add in more oil and also discover whether there is a leak) 
  2. Oil level in the bushing 
  3. 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) 
  4. Dehydrating breather (you must check both that the air passages are free and the color of the active agent. Pink means the charge needs to be changed) 
  5. Relief diaphragm 
  6. Cool fan 
  7. Bearing motor (lubricate it and check the contacts. If the contacts have worn, they should be replaced) 
  8. Operating mechanism 

Items that need to be checked quarterly or every four months: 

  1. Bushings (clean them and replace if they have cracked) 
  2. Oil in transformer (not just the levels this time. Quarterly you should check the dielectric strength and water content of the oil. The quality may need to be restored.) 

Items that need to be checked at the end of 5000 operations, or yearly: 

  1. Oil in the diverter switch of OLTC 

Items that need to be checked yearly: 

  1. Oil in the transformer (this time check the acidity resistivity, tan delta and sludge. It may need to be filtered or replaced entirely) 
  2. Oil-filled condenser bushing 
  3. Gasket joints (may need to be tightened to avoid uneven pressure) 
  4. Cable boxes 
  5. Relays alarm and other circuits 
  6. Painting 
  7. Earth resistance 

Down the line, after your transformer has been running for many years, you may need to add additional checks to this list, to measure the performance of the transformer and other things. 


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What About Dry-Type Transformers? 

Dry-type transformers rely on air to cool the system, and this difference means that they have slightly different maintenance needs. First, dry-type transformers need to have dry windings. Moisture and high humidity can de-energize areas, just as extreme fluctuations in temperature can. Your dry-type transformer may have additional maintenance needs. Reach out to us to discuss them. 

The longevity of your transformer depends on its maintenance. Trust the experts at VCM Solutions to maintain your transformers. Reach out to us to discuss your transformer inspection, maintenance, and safety check needs today. 

Transformer Selection Guide