Increased penetration of solar photovoltaic (“PV”) generation in distribution circuits raises a potential issue with load rejection overvoltages. The condition occurs with the lightly loaded feeders. If the feeder load is much smaller than the total isolated generation then the load rejection overvoltage could pose a threat of damage to equipment insulation and surge arresters. In addition, the inverter characteristics used for PV installations present their own unique impacts. Different inverter designs respond differently to the phenomenon. Pterra used a time domain simulation tool to quantify the impact of load rejection on several different circuit configurations and several different types of inverters.
The study system is shown in Figure 1.