Abstract
In this study features and factors important for thermal fields of several high-voltage electrical apparatus elements, such as high-voltage transformer input, polymer surge arrestor, bus contact and high-voltage power cable, have been considered. Stationary thermal field disturbances, caused by defects, have been studied, and possibility of their detection via monitoring data from infrared, contact and optical temperature sensors have been assumed. The features of non-stationary thermal field disturbances, taking place under pulse currents in bus connections and surge arrestors, have been analyzed, thus allowing to get information about device defects.