Effect of Harmonics on Transformers Loss of life

Abstract

The use of non-linear (solid state) loads in power system has increased the awareness of the potential reduction of a transformer life due to the increased losses. Manufacturers and users have been applying IEEE C57.110-1989 which gives a conservative estimate of loading capability of transformers. In this paper, the effect of harmonics on transformers is discussed and a thermal model to predict a transformer hot spot temperature is presented. The model considers a time varying harmonic load cycle and ambient temperature. The model is applied on 31.5 MVA, 115times9times1.67%/6.3 kV ONAF transformer