Statistical and engineering analysis of transmission system topology's influence on large autotransformer failure rates

Failure rates for large high-voltage transformers are significantly lower at multi-bank stations than at single-bank stations. It is determined that the different failure rates is statistically significant. Examination of the electrical equivalent circuit, coupled with consideration of the magnetomotive situation shows that the magnitude of through-fault current is reduced for transformers in multi-bank configurations. Since most transmission system transformer failures are due to throughfault, probabilistic-based power system planning analyses should take into account the distinct failure rates associated with single and multi-bank topologies.