Abstract: A method and apparatus for detecting the location of an incipient fault in an insulated power which includes the application of an excitation voltage to a power line to produce a partial discharge signal pulse at a fault along the power line. The surface of the power line is scanned with two axially spaced sensors disposed adjacent the surface of the power line, the sensors detecting the partial discharge signal pulse to produce discrete detected pulses. These detected pulses are combined to produce a combined signal having all amplitude level which reaches an extreme value when the fault is located equidistantly between the sensors. The sensors are moved along the power line until the fault is located substantially equidistantly between the sensors as indicated by the extreme amplitude level of the combined signal.