Power Transformer Breakdowns and Explosions

Older power transformers were originally designed to last between thirty and forty years. Surprisingly many of these transformers are still in use today after fifty to sixty years of operation. Their manufacturers did not anticipate the overwhelming increase in the electricity demand that we experience today and so the transformers are required to cope with increased loads.

The insulating materials of older power transformers comprise of cellulose and oil. Over time they absorb water which deteriorates the cellulose's insulating ability. In the case of heavy loads, water can also turn to steam which evolves in the form of bubbles. Degradation of insulating materials is one of the most important reasons for power transformer breakdown. In some extreme cases the problem can cause a power transformer explosion.

The combination of higher-than-expected transformer age - and therefore high levels of degradation - and increased loading have produced a significant increase in power transformer explosions in the USA in the late 1990's. Power transformer explosions effect both companies and society, with costs amounting to billions of USD.