In the majority of 500 kV substations, the voltage on the 500 kV busbars is regulated within a specific permissible range through the switching of 35 kV low-voltage reactors or capacitor banks, ensuring the safety and economic efficiency of system operation. Within the context of the new-type power system, reactive power fluctuations have intensified, exposing circuit breakers to extreme operating conditions such as high-frequency inrush currents, overvoltages, and frequent operations during switching. After a certain number of operations, issues like poor contact between components and severe ablation and wear of contacts can arise, leading to an abnormal increase in loop resistance and compromising the circuit breaker’s safety throughout its service life. This paper dissects and analyzes typical circuit breakers exhibiting excessive loop resistance during actual operation, with a particular focus on the service conditions of key materials such as electrical contacts and their impact on loop resistance. Subsequently, targeted optimization measures are proposed to ensure the stable performance of circuit breakers and the safe operation of the power grid.