Electrical fault protection for a large photovoltaic power plant inverter

The authors analyze the original protection design and describe changes made to improve fault protection after electrical faults caused fires in the DC wiring of a photovoltaic (PV) power plant. The zone-of-protection was extended, and fault detection and response were improved. The results suggest a need for better coordination between DC and AC fault protection philosophies that are commonly applied independently by designers. Design lessons for PV array fault protection are described to assist electrical designers in eliminating fault vulnerabilities from future PV systems. These take into account the unique electrical characteristics of PV generators, including the dispersed-rather than point-source and the current- rather than voltage-source nature of the PV array.