The Wear Resistance of the SF6 Circuit Breaker Contact System Composite Materials when Clearing Short-Circuit Currents

The article presents the results of experiments on studying the switching wear resistance of the composite materials used in the contact system of 35 kV SF6 circuit breakers during repeated clearing of short-circuit currents of up to 20 kA. Two versions of arc electrodes were considered: when using tungsten-copper (W-Cu) metal-ceramic composite materials with powder components and when using W-Cu electrode materials reinforced with tungsten fibers. For the arc electrodes made on the basis of tungsten-nickel-copper (W-Cu) metal-ceramic composite materials with powder components forming a tungsten-nickel frame impregnated with copper, two cases of components were studied: with a tungsten content of up to 70 and up to 50%. According to the study results, a composite with a tungsten content of 70% was chosen as the recommended one. For tungsten-copper electrode materials reinforced with tungsten fibers, predominant wear of the central part of their working surface and the concentration of the arc basic spot on it were found, which result in that the wear of the fluoroplastic nozzle is by 30-40% lower compared with its wear in the case of using W-Cu electrodes with powder components.