A method of detecting a fault in a power distribution system includes placing a signal on the system at a frequency F1 and then detecting a change in the signal due to a change in the impedence of the system as a result of a fault wherein the change is one of a change in phase, a change in signal tone, or a change in voltage level at the load. In one embodiment, band reject filters can be used to diminish the signal at the load or source. In another embodiment, the power source can be a periodic pulsed power source and the signal can be placed on the system during an idle phase of the periodic pulsed power.