Dynamic Resistance Measurement Based on the Whole Lifetime of Breaker Arcing Contact

The electrical lifetime of high-voltage SF 6 circuit breaker is determined by the condition of the contacts. In this paper, the electrical erosion tests have been conducted on two 40.5kV and 126kV circuit breakers to obtain the dynamic resistance curve for contacts in different erosion levels and with different DC test current. The experimental results show that: a) the normal values of main and arcing contact resistance are 50-150μΩ and 200-400μΩ; b) the contact travel of arcing contact decreases linearly with the number of erosion tests; c) the DRM with higher testing current gives more accurate result. The DRM with DC testing current higher than 1kA gives a more accurate result. The contact travel of arcing contact has an important influence on the performance of arc extinguishing chamber and the contact travel of arcing contact has been proved to be the determinant influencing factor for the electrical lifetime of the circuit breaker. Finally, diagnostic method of circuit breaker electrical lifetime has been put forward based on the parameters of contact resistance and contact travel.