Research on High-Frequency Impedance Characteristics of Damaged Circuit Breaker Closing Resistance

The closing resistor in a circuit breaker are prone to damage during operation due to extreme factors such as over-voltage, over-current, and mechanical shock, which alter their high-frequency impedance characteristics. Comparing impedance before and after damage can indicate the severity of degradation. However, the high-frequency impedance properties of damaged closing resistors remain insufficiently understood. This study investigates three classic damage types through simulation and external testing on a physical circuit breaker, validating the accuracy of the simulation results. Further high-frequency impedance measurements inside the tank examine the characteristics under varying damage degrees. Results show that external testing reflects the intrinsic impedance changes in the resistor string, exhibiting primarily resistive and inductive traits, with negligible capacitive influence. In contrast, internal measurements are affected by the tank’s capacitance, leading to a resonance point in the high-frequency range. Different damage degrees cause noticeable shifts in the resonance frequency and a gradual increase in impedance magnitude. These findings offer practical guidance for field inspection of circuit breaker closing resistor conditions using high-frequency impedance techniques.