Thermal condition assessment for power transformers operated in tropical condition

Operated transformers shall experience simultaneous stresses, for example mechanical, thermal, and chemical stresses. In general the higher the load is, the higher the stresses will be. The performance of a transformer is depended on its main insulation condition which is limited by the working temperature. By considering the insulation deterioration process and based on the failure modes and effect analysis we found out that besides overloading scheme, external disturbances and ambient condition has affected the transformer performance. Thus we rely on the loading and calculated hot spot temperature, dissolved gas analysis (DGA), and insulation quality as determined parameters of transformer condition. The boundary values of loading temperature, DGA, and insulation quality are obtained statistically while for the hot spot derived from hot spot calculation and paper insulation standard. In this paper we would like to describe our experiences in developing power transformer condition assessment based on thermal approaching.