Power Transformer is an important component in various segments right from power generation to commercial applications. Power transformers are continuously in operation since their commissioning, their ageing process are going on towards their end of life which cannot be avoided. To achieve a zero-downtime predicting the condition and lifetime of the transformer is of utmost importance. The life of a transformer is majorly governed by its thermal limitations. In oil-filled power transformers, circulating oil is hotter at the top of the winding. Adding up these various heat dissipation phenomena will end up causing “hot spots”. Hot spots are the highest temperature areas in the transformer based on flux leakage from the windings and can degrade the insulating paper making the transformer susceptible to failure.


The insulating system is a vital part, with oil and the solid insulation. The solid insulation may not be so readily accessible, while the oil is readily accessible and can be kept in a good condition for a very long time with proper care, probably for an indefinite period. However, poorly maintained oil will significantly reduce the actual life of the transformer. Since transformer life is dependent on the insulating paper, accurate temperature monitoring is vital. Increase in electricity demand also known as, heavy spike loads, will increase the temperature in power transformers (hot spots) and increase the degradation of the insulating paper. However, transformers can develop faults well before the end of their life expectancy, leading to failure and ultimately causes a breakdown of the entire system.


There are several reasons for hot spots, but we have identified top 3 reasons for the development of hot spots in transformer. Several actions can be undertaken to extend the assets life and prevent costly failures which can have financial impact. Following are the three main reasons which cause hot spots in the transformers

Following are the three main reasons which cause hot spots in the transformers

  • Dynamic Loading or Over Loading
  • Insulation Degradation
  • Through Fault Current