Estimation of Current TransformerInsulation Life with an Effect ofEnvironmental Variables

Current transformer is an important component of EHV substation & the power system. Most of the faults occurring in current transformers are due to insulation failure. Insulation aging is a function of temperature and other environmental factors such as solar radiation and wind velocity. The aging effect is produced by Hot Spot Temperature (HST). The HST value depends on the ambient temperature, the rise in the Top Oil Temperature (TOT) over the ambient temperature, and the rise in the winding HST over the Top Oil Temperature. The winding hot-spot temperature can be calculated as a function of the Top Oil Temperature and that can be estimated using the transformer loading data, top-oil temperature, ambient temperature, wind velocity and solar radiation. This paper discusses the HST with considering environmental factor and without considering the environmental. The loss of life of insulation is related exponentially to the HST. This paper presents the mathematical model of Hot Spot Temperature under variable environmental condition in MATLAB.