DC grids DC fault detection using asymmetric pole inductors

Abstract

DC fault isolation is recognized as the major obstacle against widespread development of multi-terminal meshed DC grids. To fulfill DC grid protection requirements a fast, discriminative, and seamless DC fault detection and isolation mechanism is needed. This paper presents a DC grid protection system based on using asymmetrical pole inductors (APIs) for fault detection, and hybrid DC circuit breakers (HDCCBs) for fault isolation. The pole inductors are those normally used in series with cable-end HDCCBs to limit rate of fault current development. An intentional mismatch between positive and negative poles’ inductors is proposed for autonomous fault detection using the difference between positive and negative poles’ DC voltage magnitudes measured at all cable-ends. Better accuracy in discriminative symmetrical fault detection, and less sensitivity against fault impedance are achieved using lower series inductors compared to rate of change of voltage (ROCOV) technique as the most effective approach proposed so far. In order to investigate the proposed technique, a 2 GW symmetrical monopole DC grid equipped with proposed protection system is modeled in PSCAD. Simulation results are demonstrated to show the capabilities of the proposed protection system in fast and discriminative DC fault detection.