Impact of PV on distribution protection system

This paper investigates the impacts of PV interconnection on the protection systems of a distribution network, especially when power flow is reversed in high penetration scenarios. A Florida based substation and its six-feeders were selected for the study. The system was slightly modified to make it a notional system that still closely represents the actual system behavior from the point of view of system protection. The main modification is in the representations of loads, where all the loads were represented by fewer aggregated loads on each feeder. One of the feeders is 9 miles long and has a 12.6 MW (AC) PV plant connected to the primary side of the feeder at a distance of 4.8 miles from the substation. The feeder has an average load of approximately 11 MVA that makes it a contender for a high penetration (more than 100%) feeder when PV reaches its peak generation. The model of the entire substation, its feeders and protection system has been built using a high fidelity transient simulation tool RSCAD. Initial simulation results indicate that if protection devices are coordinated properly, a reverse power flow does not create any nuisance trip or malfunction of the protection system. However, based on the location of the PV plant with respect to the fault, slight change in the trip time of the time-overcurrent relays was observed.