The reliability and continuous performance of the power transformer is one of the vital key to profitable power generation and transmission. However, due to the practice of minimizing the capital expenditures of electrical power system, it is very common to operate these equipments close to the limits of their design such as with the maximum load capability. The cost of acquistion, replacement, transportation, installation and repairs of power transformer is among the highest cost in the system. Its failures will create losses of revenue and if catastrophic, there wil be substantial cost in terms of the destruction of the connected equipment, environmental damage and unexpected use of resources.

Over the decades, transformer failures have been common and costly. According to the statistics done over a one year period, it was discovered that 730 transformer explosions happened in the USA in the year 2001 alone. Many experts anticipate that the number of failures will increase significantly in the near future, from 1% in 2001 to 2% in 2008.

Insulation failure is the first cause of failure of power transformer, and the second leading cause of failure of power transformer is insulation deterioration. Therefore, insulation strength within the transformer plays a key role in affecting its life expectancy. Of all the common causes of transformer failure, insulation strength deterioration is one that can be continuously monitored. Through this continuous monitoring, transformer failure could have been avoided.