Circuit Breaker Contact Diagnostics Based on Dynamic Resistance and Fuzzy Logic

Summary

This paper describes the application of the dynamic resistance measurement (DRM) for assessing the condition of power circuit breakers contacts. In the DRM tests, a resistance curve is generated, contemplating resistance values referring to the main and arcing contacts regions. The tests were performed with minimum oil circuit breakers (MOCB) of 800 A/15 kV/12.5 kA and 2.000 A/72,5 kV/31.5 kA, and a SF6 circuit breaker of 1.650 A/72,5 kV/25 kA. To perform the DRM tests, a system has been designed and developed, which employs a 4-channel digital oscilloscope, a stationary battery of 12 V/220 Ah, resistors to limit the current from battery , current and voltage sensors and a personal computer. The system is able to determine the dynamic resistance values since the beginning of the contact opening until total separation. As consequence, an algorithm was developed to extract the DRM curve features, and a Fuzzy logic based system to estimate the level of contacts degradation. It was observed that the DRM curve area is directly proportional to the contacts degradation level. Results indicate that the contacts degradation level is directly associated with the DRM curve area, allowing an accurate diagnosis of the main and arcing contacts condition. The application of Fuzzy logic allowed the estimation of the contacts degradation level.

Additional informations

Authors

Zhang Qing, Kurrat Michael, Chen Xi