Influence of excessive contact resistance on electrothermal characteristics of conductive connection structure

Abstract

One of the common structures at the end of the bushing is a plug-in structure, in which the male and female heads are plug-in connection, and the entire structure conducts through strap contacts. Due to the combined effects of electricity, force and heat, the contact between the strap contacts and the guide rod is easy to be poor, and the contact resistance is easy to increase. In actual operation, the temperature rise is difficult to obtain by measurement. Thus, through COMSOL electro-thermal coupling simulation, it is found that after the contact resistance exceeds the standard 320μΩ, the contact point is the highest temperature of the whole structure, which is easy to cause the decomposition of SF6 gas and threaten the safety of the bushing. As the contact resistance increases, the temperature of the entire structure increases, and the maximum temperature and temperature rise are basically linearly related to the contact resistance. When the contact resistance is 3370μΩ, which is about 10 times the standard, the overall maximum temperature reaches the limit of 120°C in the IEC60137 standard. The simulation provides guidance for improving the reliability of the bushing and the optimization of the electrical connection performance.