Evaluation method of contact erosion for high voltage SF6 circuit breakers using dynamic contact resistance measurement

To investigate the relations between DRM characteristics and contact erosion, the DRM results of high voltage SF6 circuit breaker at various degrees of erosion obtained from the designed experiments are presented. The experiments demonstrate that with the degradation of the contacts, the average arcing contact resistance (Ra) increases, and the arcing contact wipe (Da) decreases. Then, the simulation of the erosion test is performed to analyse the relations between Ra and Da and the contact performance. The results show that with the decrease of Ra, the threshold of Da to ensure the success of the current commuting from the main contacts to the arcing contacts becomes shorter. Moreover, the influence of the electrical stress on Ra and Da are investigated. Results demonstrate that Ra reflects the influence of arc by-products and contact geometry caused by electrical stress, and that Da reflects the influence of the interrupted current, the arcing time, the contact geometry, and the contact material. Finally, an evaluation method of the contact erosion for SF6 circuit breaker based on DRM is proposed.