Detection and Localization of Ground Faults in PV Strings Using a Simple Voltage Comparator

Reliable detection and localization of ground faults in photovoltaic (PV) strings is essential for preventing hazardous conditions such as electric arcs and fires. While modern inverters can detect initial ground faults, they rarely provide fault location information, which complicates remediation. Older inverters and small rooftop PV systems often lack detection capabilities entirely, increasing fire and electric shock risks in these widespread installations. This paper proposes a cost-effective voltage-comparator method based on capacitive-resistive impedances connected to the positive and negative terminals of each string. Voltage comparison across these impedances enables reliable fault detection and localization. The method is applicable to any PV modules or inverters and is validated on a real PV system, with experimental results confirming its effectiveness.