Conflicts in the distribution network protection in the presence of large photovoltaic plants: the case ofENDESA

This paper describes a hitherto unstudied malfunction that can occur in the protection system of distribution networks (DNs) in the presence of large photovoltaic plants (LPVPs). The focus here is on the phase-balance current (PBC) protection of overhead or blended feeders back-fed by LPVPs. This study used the DNs belonging to ENDESA Distribución Eléctrica S.L.U. In the ENDESA utility company, PBC protection (ANSI 46) is an obligatory DN protection practice for overhead or blended feeder types. Low power quality or two ferroresonant states were found to be the causes of the malfunction of PBC protection, which led to its untimely tripping. The results of this study highlight the need to modify current DN protection practices and to elaborate new power quality requirements for PV-distributed generation (PV-DG). Since PV-DG penetration in DNs is steadily increasing, regulators and DN operators should implement more effective practices and guidelines to offer better power quality to customers.