Reliability parameters and properties of medium voltage/low voltage transformers

MV/LV transformers are the basic elements of any power distribution system. Their reliability characteristics significantly affect quality and reliability of power supply. Due to the lack of current research in the field, the author carried out extensive reliability research on MV systems and power distribution stations on the premises of two large power suppliers in Poland. The paper provides a failure frequency analysis of transformers installed in MV distribution networks. Reliability models and transformer recovery times, failure-related shutdowns, power supply breaks, and volume of unsupplied energy were determined. Also were analysed seasonal incidence and causes of failures.