An improved transformer top oil temperature model for use in an on-line monitoring and diagnostic system

In this paper we examine dynamic models of transformer top oil temperature for use in an on-line monitoring and diagnostic system. Data taken from large transformers in the field indicate that the IEEE model of top oil temperature rise over ambient temperature does not adequately account for daily variations in ambient temperature. We propose a modification that acciirately predicts top oil temperature and can be implemented in an on-line system. This model is verified using data from a large transformer in service.