Ground fault protection in ENEL Distribuzione - experimental MV loop line

The presentation describes the design and implementation of a new protection system consisting of a permissive overreach (PO) pilot relaying scheme with directional overcurrent relays for both phase and ground faults supporting closed-loop operation in an MV network; attention is focused on ground fault relaying of loop networks operated with ungrounded or compensated neutral. Relevant zero-sequence quantities are studied and changes to relay settings are proposed and verified by detailed simulations. The system, developed within the framework of "Piano Operativo Interregionale" (POI) funded by the Italian Government, will soon enter service in an ENEL Distribuzione (Enel-D) network.