Research On Making Erosion Of Arcing Contacts Material Used For Circuit Breaker Of Capacitor Banks Switching In UHVAC Engineering Projects

In the UHVAC system, the electrical endurance of circuit breakers used for capacitor banks is at least 3000 times in order to satisfy the requirement of reactive power compensation. However, the lifetime of existing dedicated circuit breakers can only reach hundreds of times, and its shortage lies in the anti-erosion ability of arcing contacts. Due to the significant difference between making and breaking erosion behavior of arcing contacts, it is urgently needed to understand making erosion behavior and characteristics through experimental study and theoretical analysis. It can also provide a reliable basis for the selection of arcing contact material as well as the design of the interrupter structure and operating characteristics.According to the analysis of the arcing contact erosion, making erosion contains physical processes: 1) pre-breakdown arc erosion, 2) post-arc friction and wear, which is different from breaking erosion. On this basis, making erosion experiments and arc erosion experiments of arcing contacts were designed to study the characteristics of making erosion under different experimental conditions, and to distinguish the effect of two physical processes. Optimum selection experiments of arcing contact materials were designed, and typical arcing contact materials were compared, and some possible improvement of arcing contact were put forward. Finally, according to the making erosion characteristics and microstructure of the arcing contacts, two models to calculate the electrical endurance were proposed, based on two failure modes: 1) restriking, 2) time sequential inversion of operation.The research shows that outer skeleton that protects arcing contacts is worn away because of the post-arc friction and wear process, thus making erosion is more serious compared to the breaking erosion under the circumstance of switching capacitor banks. During the arc erosion, the mass loss of arcing contacts is determined by the arc energy, and the pre-breakdown arc erosion has a great impact on the post-arc friction and wear process. When the arc energy is relatively small and large, the post-arc friction and wear process plays a leading role, and the arc erosion process has great influence on the making erosion within a certain range. In the case of low speed of moving contact, arc energy plays a leading role, and impact force plays a dominant role in a high speed case. Manufacturing process and control of arcing contacts will affect the anti-erosion ability to a certain extent.