Lifetime evaluation of HV transformers

Power transformers are one of the most important equipment in power substations and distribution systems. As its price is about 55% of the whole substation price, it can be called the valuable element in the power grid. Thus, the lifetime management based on economical and technical indexes is highly essential for facilitating asset management and achieving higher reliability in the power system. This study presents the factors that can affect ageing transformers and analyzes oil test parameters. Dissolved gas analysis (DGA) is performed and some existing methods for evaluating of transformer operation based on DGA are compared. The pros and cons of each method are shown and a simple method to assess transformer condition is found. Also, three power transformers with real values and oil samples are studied for lifetime evaluation, and some possible solutions are proposed for better operation and maintenance.