An adaptive protection scheme for multiple single-phase grounding faults in radial distribution networks with inverter-interfaced distributed generators

Abstract

Conventional zero-sequence current (ZSC) protection relays for low-resistance grounded systems (LGSs) are confronting challenges due to the risk of multiple single-phase grounding faults (MSGFs) and the ongoing increase in the penetration of inverter-interfaced distributed generators (IIDGs). Such issues concerning false or failure tripping require a reconsideration of traditional solutions. This paper presents a novel adaptive ZSC protection scheme using the current-compensation method for LGSs with IIDGs. The mechanism for in-phase MSGFs and out-of-phase MSGFs in LGSs with IIDGs is formulated. The ZSC calculation method for LGSs with IIDGs is introduced via the zero-sequence compensation factor, where the feeder ZSC generated by MSGFs is converted to its counterpart during a single fault. With the manufacturing message specification (MMS) protocol in IEC 61850 that is selected to help share IIDG information, the adaptive ZSC protection philosophy is implemented, which automatically amends the ZSC and sets the protection settings of all relays in real-time. The validity of theoretical analyses and the performance of the protection scheme have been demonstrated by using the PSCAD/EMTDC simulation under various scenarios.