A first switch for connection in a first circuit path between a PV panel string and an inverter in a power system, and a second switch for connection in a second circuit path across an output of the PV panel string, are normally closed and open, respectively, during non-fault operation of the power system. Both series and parallel arc faults in the power system can be extinguished by further control of the switches. Arc fault detection could be based on probabilistic frequency analysis of current or power flow measurements in the PV panel string, current or power imbalance, interruption in communications with the PV panels, or combinations of these techniques.