A Novel DC Distance Relay for MVDC Microgrids

Abstract

Detecting faults in DC microgrids faces numerous challenges in terms of fast detection requirements, sensitivity against low- and high-resistance faults, and selectivity. This paper proposes a novel local-measurement-based DC distance relay for DC microgrids that addresses these challenges. The relay’s power circuit integrates an inductor at the end of each line. Additionally, it employs auxiliary components with a peak detection circuit (PDC) for capturing and processing different waveforms at the instant of fault occurrence. Local measurements of the relay voltages and currents are used to identify local forward faults, and to estimate the fault location within a short time frame. Furthermore, the relay provides backup protection for forward external faults on adjacent lines. The concept is first verified on a simple feeder. Then, a meshed DC microgrid, modeled in PSCAD/EMTDC environment, is used to further verify and evaluate the performance of the proposed scheme. Various fault scenarios are performed to examine the relay’s performance under different fault conditions. The results highlight the speed, selectivity, and sensitivity of the proposed method against bolted, low- and high-resistance faults.