Regular Maintenance For Oil-Filled Transformers

May 30, 2023

Regular Maintenance is Key to Keeping Your Oil-Filled Transformers Functioning Properly

Maintaining the functionality of your oil-filled transformers requires regular maintenance. Your transformers will be more prone to encounter problems without routine maintenance, which could snowball into more serious operational issues including system failure. When caring for your machinery, you don't have to rely solely on proactive or condition-based maintenance. Any and all equipment issues can be addressed earlier and with greater results, if you stay ahead of them.

The Importance of Regular Maintenance

Regular maintenance is important for a number of reasons.

First and foremost, it helps to prevent small problems from turning into big ones. It's much easier—and cheaper—to fix a problem before it turns into an emergency.

Secondly, regular maintenance helps extend the life of your equipment. By catching issues early and addressing them promptly, you can avoid costly repairs down the road.

Finally, regular maintenance helps ensure that your equipment is always operating at peak performance. This is important for both safety and efficiency reasons.

How often you need to perform maintenance will vary depending on the type of equipment you have and how often it's used. But as a general rule of thumb, it's a good idea to perform some sort of inspection or service at least once a week. This can be as simple as checking fluid levels or doing a visual inspection for signs of wear and tear. More complex pieces of equipment may require more frequent service. Consult your owner's manual or a qualified technician to determine the best maintenance schedule for your particular needs.


For oil-filled transformers, daily maintenance routines should include oil and temperature checks. Check if the ambient, winding, and oil temperatures are within acceptable ranges. The oil level gauge ought to change as the temperature changes, and if it's a magnetic model, it ought to rotate in response to the presence of a magnet. It’s necessary to replace the indicator if it fails to do one of these things.

Compare the load voltage and current to the rated values to analyze them. To prevent electrical harm, the load settings should be compatible with the type of transformer you're using. An electrical failure can also be avoided by keeping your ground current, differential, and overcurrent relays in top condition.

For dry-type transformers, the noise level is frequently a more pertinent performance metric. However, if your oil-filled model makes a lot of noise, you must identify the potential causes. High noise levels frequently come from the coils, cooling system, or core of the transformer.


Your weekly maintenance plan should contain steps, like checking the oil level indicator quickly and comparing it to the oil temperature to determine the oil level in your transformer, performing a thorough visual examination of the transformer's exterior, looking for any stains and paint chips, and examining the gas collection in the Buchholz relay. You should also ensure that there are no oil leaks and tight gasket joints in the radiators and examine any vent for a pressure relief mechanism fitted on a cap to ensure adequate sealing. Look for indications that the pressure release device is functioning properly. All of this only takes a few minutes a week, but it might save you weeks of downtime if the transformer malfunctions due to poor maintenance.

Monthly or Quarterly

If not required sooner, some tasks will only need to be completed periodically or quarterly. For instance, you could top off your oil, check the oil's dielectric strength, or inspect your cable box and terminal bushings every few months to see if they are sufficiently tight or if there is any damage. At each yearly checkup as well as once per month, the bushings should be inspected for cracks. The auxiliary circuits and accessories of the transformer may also be inspected and cleaned every six months.


Add the following to the calendar for your annual maintenance plans:

● Check the pressure relief devices located on the lid, the pressure relief valve and/or Schrader valve, and the surge relay annually for wear and tear.

● Every year, check the temperature indicators and the off-circuit selector and replace them if necessary.

● Check the weatherproof seals on the marshaling boxes and clean them.

● Check the safety relays on the transformer for insulation resistance.

● Check the resistance of the fan or oil pump motors.

● Check for leaks on the top of the transformer device near the pressure relief tank every three to five years.

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