New diagnostic method of winding insulation degradation in power transformers based on partial discharge characteristics

A resolved gas analysis method has been one of the most important evaluation methods of the degradation of insulation paper in power transformers. However the resolved gas analysis method requires special care to sample the oil and takes time to get the result. Instead of resolved gas analysis method to estimate the degradation of the paper, it is found that a simple relationship between the partial discharge magnitude and the decrease of polymerization, resulting from a lot of field measurements of power transformers. It is also found that a certain partial discharge pattern strongly correlates to the occurrence of acetylene in the insulation oil. This paper proposes a new evaluation method based on the partial discharge magnitude and patterns. The new method may give the maintenance staffs of power transformers a very effective and reliable diagnosis method of insulation paper degradation.