Wear Mechanism and Mass Loss Characteristic of Arcing Contacts in SF6 Circuit Breaker in Making Process

Abstract

Large-capacity capacitor banks have been used to control the reactive power of ultra high voltage ac grid in China. The high switching inrush current of SF6 circuit breakers used for large-capacity capacitor banks has caused great mechanical wear after arc ablation, which leads to the serious erosion of the arcing contacts of the circuit breakers, thus shortening the electrical life. To improve the electrical life of circuit breakers, the wear mechanism and mass loss characteristic of arcing contacts in the making process were studied in this paper. Through erosion experiments in the making process and arc ablation experiments in the circuit breaker test device, the wear mechanism and the mass loss characteristics were analyzed via the detection of worn contacts and wear theory. At normal temperature, the wear mechanism is mainly abrasive wear. At high temperature, the wear mechanisms in three stages mainly include adhesive and abrasive wears. When the closing inrush current amplitudes are 10, 20, and 30 kA, the mass loss of mechanical wear is greater than that of arcing ablation. The total mass loss and mass loss rate per unit charge increase with the interference radius between two contacts and with test current. However, with current amplitude higher than 20 kA, the total mass loss rate decreases. Suggestions to reduce wear are proposed to improve the electrical life of circuit breakers.