A Novel Method for Determining the Electrode Temperature Effect on Post-Arc Breakdown Characteristics

During the post-arc stage of the interruption process, hot gases, high-temperature electrodes, and metallic macroparticles could strictly hinder the recovery of dielectric strength. Despite many studies focusing on the mechanism of the post-arc phenomenon, there is still a lack of comprehension determining the role of electrodes during the breakdown process. In this paper, the electrode temperature after current zero is measured by using the two-color-pyrometry method combined with the narrow band-pass filters and an optical splitting device. Adopting a repetitive pulse power supply, and heating the electrode with a high-power laser, the temperature effect of WCu electrodes on post-arc breakdown voltage in atmospheres is quantitatively determined. Both for the cathode and the anode, the threshold effect of the electrode temperature on the breakdown strength is observed. However, it is found that the cathode temperature has a more pronounced impact on the breakdown voltage compared to the anode temperature; the cathodic critical temperature range for the threshold effect is 1350K-1500K, while the corresponding anodic critical temperature range is 2400K-2500K. By introducing the voltage ratio coefficient of the electrode, we show strong evidence that the higher arc energy could prolong the effect of electrode temperature on the recovery of the post-arc dielectric strength.

I. Introduction

As the pivotal protection unit in low-voltage and medium-voltage electrical power grid, DC Air circuit breakers has been widely used in DC transmission and distribution systems, such as rail transit and vessels. Recently, DC air circuit breakers are developing towards the goal of large breaking capacity and fast breaking performance, for dealing with the difficulties of short-circuit current interruption in the DC system. However, the well-known phenomenon of post-arc breakdown, usually followed by the arc reignition, could easily lead to the interruption failure of the DC air circuit breaker, which limits the further improvement of its breaking capacity [1].