Analysis of mechanical damage characteristics of closing resistor of 800kV tank circuit breaker with multi-physical field

The closing resistor sheet in the 800 kV tank circuit breaker, used in Northwest China, has been repeatedly damaged due to internal stress concentration during the opening and closing processes. This paper utilizes thermal field emission scanning electron microscopy to analyze the microstructure and composition of the resistor sheet. Alumina ceramic, the primary component, significantly influences the sheet’s thermal conductivity and mechanical properties. Meanwhile, the carbon component, though minor, provides an effective conductive path. The microhardness of the resistor sheet at different radial positions was measured via a microhardness test system, and it was found that the hardness of the resistor sheet at various radial positions was different and had the minimum value near the outer edge of the resistor sheet. Using multi-physics field analysis software, the 800 kV tank circuit breaker with a closing resistor was modeled, and the stress changes in the closing resistor under impact loads were analyzed. When the surface of the closing resistor was uneven, the stress concentrated on its outer edge, resulting in easily damaging the outer edge.