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

Dynamic contact resistance measurement (DRM) is an effective technique to evaluate the contact conditions of high voltage SF6 circuit breaker. However, the relations between DRM characteristics and contact performance remain ambiguous, the influence of the electrical stress on the DRM curves is equivocal as well, and there is no contact erosion evaluation method based on DRM. 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 (R-a) increases, and the arcing contact wipe (D-a) decreases. Then, the simulation of the erosion test is performed to analyse the relations between R-a and D-a and the contact performance. The results show that with the decrease of R-a, the threshold of D-a 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 R-a and D-a are investigated. Results demonstrate that R-a reflects the influence of arc by-products and contact geometry caused by electrical stress, and that D-a 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. (C) 2017 Published by Elsevier B.V.