An approach to mitigate the impact of distributed generation on the Overcurrent Protection scheme for radial feeders

Increased distributed generation (DG) presence on radial distribution feeders is becoming a common trend. The existing overcurrent protection (OCP) scheme on such feeders consists mainly of overcurrent protection devices (OCPDs) such as fuses and reclosers. When DG is placed on the remote end of a 3-phase lateral, the radial configuration of the feeder is lost. As a result, OCP issues may arise which lead to permanent outages even when the fault is temporary. This paper presents a new approach that revises the existing OCP scheme of a radial feeder to address the presence of DG. The fuses on the laterals with DGs are removed and multi-function recloser/relays (MFRs) are added to address three specific OCP issues; fuse fatigue, nuisance fuse blowing, and fuse misoperation. The new approach requires no communication medium, provides backup protection for the DG unit, and allows the remaining laterals to retain their existing protective devices. The results are reported using the IEEE 34 node radial test feeder to validate the new approach and the IEEE 123 node radial test feeder to generalize the approach. The new approach completely mitigated the fuse misoperation and nuisance fuse blowing issues and most of the fuse fatigue issues that were present on the radial test feeders.