Internal State of Fuse Arc Differentiating Interruption Success and Failure in Fuse‐Semiconductor DC Circuit Breaker

Abstract

For the realization of sustainable society installing renewable energy sources, we have proposed a compact, low‐cost, versatile DC circuit breaker that combines a fuse and a power semiconductor. However, even under the same interruption conditions, there are cases where the interruption success and failure are observed probabilistically; the reason for this is still unknown. In the interruption failure, thermal reignition of an arc discharge occurs inside the fuse under transient recovery voltage. In this study, the spatiotemporal dynamics of the fuse arc was diagnosed for both interruption success and failure by a voltage–current waveform recording, high‐speed arc‐emission videography and borescope‐integrated optical emission spectroscopy, in order to identify the difference between the interruption success and failure. The waveform recording and videography demonstrated that at the arc initiation inside the fuse, the radial arc length for the interruption failure was longer than the interruption success. In the current interruption phase, the radial arc length was still longer, axial arc length was shorter, and arc column resistance was lower for the interruption failure. Further, the optical emission spectroscopy showed that localized regions with higher temperature and electrical conductivity existed for the failure in the current interruption phase. From these results, the dominant factors differentiating interruption success and failure were identified as the arc shape and electrical conductivity of the arc. To improve the interruption performance of the fuse and our DC circuit breaker, it is effective to increase the axial arc length, suppress the radial arc length, and reduce the electrical conductivity of the arc. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.