Lumped RC Thermal Network Method Applied to Transient Temperature Calculation of High Voltage Bushing and Its Insulation Life Assessment

Abstract

To analyze how the internal transient temperature of the high voltage condenser bushing varies with its short-time current carrying capacity and long-aging properties, lumped RC thermal network model applicable to the structure of HV bushing is proposed. This model considers three heat transfer modes of the conduction, the convection and the radiation, and the changing relationship between material properties and temperature and the the thermal RC network topology is realized based on the MATLAB/SIMULINK. In the example of 550kV oil-SF6 bushing, the calculation results of transient temperature thermal network are in good agreement with the actual temperature rise test results which proves effectiveness and practicality of lumped RC thermal network. We used the thermal network to confirm the periodic transient variation at the hottest spot of HV bushing and analyze the shot-time current carrying capacity by step load curve fitting circadian cycle change load. Finite element method and thermal network method are used to get the electric and thermal stress respectively and HV bushing long-aging properties analysis was conducted based on classic ZHURKOV and CRINE electric and thermal combined aging model. This paper applies lumped RC thermal network method to transient temperature calculation and internal insulation life assessment of the HV bushing, reinforced classic bushing design method only considering rated steady-state operating conditions and has theoretical guidance on assessing short-time current-carrying capacity and long-aging properties in high voltage bushings.