The impact of PV generation and load types on the impedance relays during both balanced and unbalanced faults

Abstract

Photovoltaic (PV) power generation and the types of connected loads both have an effect on protective impedance relays' readings. This paper investigates this effect in a real distribution system installed in the State of Kuwait. It is found that both the dynamic loads and the PV plants have considerable effects in the relay impedance value, which vary according to the load type, PV connection, and fault location. Both single phases to ground fault (unsymmetrical fault) and three-phase fault (symmetrical fault) are investigated. When single line to ground fault occurs at the PV bus (far from relay location), the dynamic loads increase the relay impedance, while the PV plant decreases the relay impedance. When a single phase to ground fault occurs at the relay bus (load bus), the dynamic load decreases the relay impedance, and the PV plant increases it. For a three-phase to ground fault at the relay bus, both dynamic load percentages and PV plant power generation have no effect on the protective relay impedance readings. At this condition, the relay impedance totally depends on the fault resistance. The main finding of this paper is that both the load type (especially dynamic load) and the PV plant have dominant effects on the protective impedance relay reading and setting. The distribution system planners and operators must consider the PV plant and types of load during designing, setting, and adjusting the protective impedance relays. The most important point in this paper is considering real case study. This means that the obtained results are more realistic than the assumed system in the other research.