Power Transformer Failure: The Background

Let's describe the origin of typical power transformer failure based on some USA statistics.

According to William Bartley from Hartford Steam Boiler - Inspection and Insurance Company - the overall load on power transformers has been increasing for several decades.

Significant industrial growth after the World War II caused a large increase in the number of transformers in electric utilities. Most of the power transformers from this era are now in or approaching the end-of-life stage of their life cycle.

Based on U.S. Commerce Department data, the power transformer installations reached a peak in the USA in 1974. That equipment is now over 30 years old. Capital spending on power transformer installations is now very low, which is why the average age of installed power transformers continues to rise.

Along with declining installations of power transformers, power consumption grows at a rate of 2% per year. A decrease in capital spending has led to an increased overall power transformer load.

Power transformers are expected to last 30 to 40 years. However in the 1975 study, it was found that the average age at the time of power transformer failure was 9.4 years.

In a 1985 study by Hartford Steam Boiler, the average age of a failed power transformer was 11.4 years.

Significant expenses on aging power transformer replacements justify the investment in power transformer monitoring and diagnostics.

Power Transformer Failure: The Moisture

According to William Bartley, the increase in moisture in power transformers can be caused by floods, leaky pipes, leaking roofs and water entering the tanks through leaking bushings or fittings.

Power Transformer Failure: Deterioration of Insulation

Insulation deterioration is another cause of failure over the past 10 years. The average age of the transformers that failed due to insulation deterioration was 17.8 years - a far cry from the expected life of 35 to 40 years! In 1983, the average age of failed power transformers was 20 years.