THE INFLUENCE OF EXTRANEOUS SOURCES OF THERMAL ENERGY ON THERMAL STABILITY AND BREAKDOWN VOLTAGE OF ELECTRICAL INSULATION DURING ITS THERMAL BREAKDOWN

Abstract

The article is devoted to the analysis of thermal breakdown of insulation of electrical and power equipment due to disturbance of its thermal balance. The analysis was performed within the simplest model of thermal breakdown while ignoring the temperature distribution in the insulation volume. Particular attention is paid to the influence of extraneous sources of thermal energy on the thermal stability and the breakdown voltage of the electrical insulation structure. From the heat balance equation and the condition of thermal balance disturbance between the total thermal power in the insulation and the heat transferred into the surroundings, have been found analytical expressions that take into account the influence of extraneous sources of thermal energy on the critical operating temperature and the breakdown voltage of the insulation. The influence of extraneous sources of thermal energy on the dependence of the breakdown voltage on the dielectric parameters and the cooling conditions was analyzed. It is shown that the breakdown voltage of the insulation decreases exponentially with the increase of the power of extraneous heat sources and the temperature coefficient of tgδ, as well as the deterioration of the heat transfer conditions. It is established that the critical dielectric losses in the insulation leading to the breakdown do not depend on the power of extraneous sources of thermal energy. It is proposed to increase the electrical insulation safety factor for breakdown strength relatived to its operating voltage, taking into account the extraneous sources of heat, to ensure the stability of insulation against thermal breakdown in the presence of extraneous sources of thermal energy. References 10, figures 3.