Analytical Investigation of Current Imbalance in Metal Oxide Surge Arrester Bank Under DC Short Circuit Test-Bed

Abstract

Electronic devices and power systems are vulnerable to transient overvoltage caused by lightning strikes, switching operations, and system faults. In DC circuit breaker applications, metal oxide surge arresters (MOSAs), composed of multiple metal oxide varistors (MOVs), play a critical role in absorbing fault energy and limiting overvoltage during interruption processes. However, MOVs may exhibit non-uniform V-I characteristics due to manufacturing tolerances, differences in cooling performance, and progressive aging under repeated surge current and overvoltage stresses. Such non-uniformity can lead to current imbalance within a MOSA bank, resulting in uneven energy absorption and degradation of overall overvoltage protection performance. In this paper, the impact of current imbalance in a MOSA bank is investigated using a PSCAD/EMTDC-based impulse current test-bed model. A virtual MOV impulse current test environment is implemented to analyze current sharing behavior under different MOV degradation conditions. The degradation level of individual MOV units is represented by controlled variations in their V-I characteristics to reproduce non-uniform degradation scenarios. The resulting current imbalance is quantitatively evaluated in terms of transient interruption voltage (TIV) and absorbed energy. The simulation results indicate that progressive MOV degradation exacerbates current imbalance and may degrade the overvoltage protection capability of the MOSA bank.