Integration Issues of Solar PV in Distribution Feeder Protection Schemes

The growth of solar photovoltaic (PV) systems in distribution networks has brought about new challenges to the operation of protection devices. The new and irregular bidirectional flow patterns from PV systems may complicate the coordination of protection relays designed to detect faults. This paper highlights some of the more concerning operational scenarios of PV systems at the farm level on typical time-current overcurrent grading of Type 51 relays. A number of simulation case studies are carried out for a small radial-type distribution system considering different PV penetration or irradiance levels, fault locations and PV sites. The impacts on overall protection coordination are discussed.