Improvement of voltage transformers overvoltage problems in MV networks

Abstract

An investigation conducted almost 10 years ago revealed that one of the causes for transformer breakdown was ferroresonance effects. As a result a new specification for the voltage transformers was issued by Estonian Power Company. Now the first of transformers with improved characteristics have been in service for years, any further breakdowns have been experienced. This paper looks at the improvements to the specifications that leaded to the improvement of the voltage transformers reliability.