Simulation of heat exchange between a digital instrument transformer and its environment for operation in emergency and unfavorable weather conditions

Abstract

Abstract Reliable functioning of electric power grids to a large extent depends on the serviceability of each unit in the given power system, subject to the impact of various unfavorable factors, namely grid operation mode and weather conditions, such as elevated ambient temperatures, insolation and no-wind. These environmental parameters have a significant negative impact on the process of heat removal from electrical equipment, which may result in its overheating and breakdown. ISPEU staff have developed and put into operation innovative design digital current and voltage instrument transformers. The purpose of the present study is to examine the impact of insolation, ambient temperature and emergency operating modes on the thermal state of transformers. A mathematical model of heat exchange for a 6(10) kV transformer was developed and verified with the results of physical experiments conducted in an environmental chamber. Heat exchange between the transformer and its environment was simulated for a July day in Sochi in nominal and emergency operating modes, and also with various values of heat conductivity of electrical insulation sealant used. It was discovered that maximum influence on transformer thermal state is exerted by self-heating of instrument resistors at elevated voltage levels.