Fault current and overvoltage calculations for inverter-based generation using symmetrical components

This paper presents symmetrical component calculations for expected single line-to-ground fault (SLGF) currents and associated over voltages on a typical distribution circuit with solar photovoltaic (PV) inverter-based generation. The analysis is based on representing the PV inverter as a current source. This paper proposes an ideal Norton´s equivalent model for the PV inverter. Results show that a ground source in the PV interconnection transformer will reduce the temporary overvoltage (TOV) seen on the feeder, when the PV backfeeds a SLGF. However, this grounding is not as effective as with conventional generation. Feeder load plays an important role in limiting TOV magnitudes to acceptable levels.