Manufacturers and suppliers of low voltage transformers India bring this article to explain the real causes of overheating of transformer oil and how one can avoid it.

What is overheating in transformer?

When the transformer gets heated and surpasses the maximum heating point due to variety of reasons is known as overheating in transformer. Overheating cause transformer loss, weakens the insulation, and reduces the service life of the unit.

What causes overheating of transformer?

There are multiple reasons to overheating in a transformer; some of them are as under-

  1. Overloading
  2. Excess current in the neutral of the transformer
  3. Issues in cooling system
  4. High harmonic content in the power supply
  5. Sustained over-voltages


Excessive loading can be a reason behind overheating of transformer. Manufacturers rate the transformers in kVA. This type of rating is dependent on temperature. Some models or units have two kVA ratings. One rating is for below a specific ambient temperature, while another rating is above the ambient temperature.

Excess current in the neutral of the transformer

It is usually caused by high zero sequence harmonic components. Experts resolve this by proper grounding through a zig zag transformer.

Issues in cooling system

There can be malfunctioning of the cooling equipment like blockages in the cooling oil circuit. Cooling fan failure during operation in the case of forced air cooling systems.

High harmonic content in supply

High harmonic loads can result in overheating in the transformer. It is crucial to identify these loads and take appropriate measures such as harmonic filters implementation.

Sustained Over voltages

Over voltage supply that exists for a long period of time can stimulate the transformer and cause overheating.

What causes transformer oil overheating?

There are top six reasons of transformer oil overheating-

Insulation overheating

This type of overheating is form inside paper insulation which is use to insulation transformer winding and cellulose paper product. Whenever there is transformer overloading, the transformer winding will be responsible for generating heat and cellulose insulation. This insulation overheating is mainly checked by transformer oil testing method.

Testing transformer oil after showing result high CO2, CO, and generate ethylene or methane.

Insulation liquid overheating

The insulation liquid overheating is a different issue to be measured by transformer oil testing method. After completion of the testing, if the result reveals the presence of high thermal gases like ethane, methane, and ethylene, etc. then it is the case of transformer oil overheating.

Corona overheating

Corona is produce and consider to be partial discharge of the transformer that occurs when there is high electrical stress.

Arcing overheating

Arcing are produced in transformer to show breakdown of the insulation. The arcing is the most serious condition measured in transformer oil testing. It requires high energy to produce arcing.

Screen testing overheating

The testing involves electrical breakdown, power factor, acidity, and inter facial tension and insulation color.

It is equally required to test transformer oil during time intervals to have smooth operations. Manufacturers of low voltage transformers India are also providing oil immersed transformers and the maintenance services to their customers at low price.

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