Abstract: A method of locating incipient faults that generate partial discharges in an AC power distribution system includes detecting at least one spike in a PD pattern generated by such system; getting the voltage wave of the AC power in the system; detecting a phase of such spike with respect to the voltage of the AC power; and locating an incipient fault where such phase is below a predetermined threshold. An apparatus includes at least one sensor of electrical pulses, means for getting a synchronism signal with a power supply of the power distribution system, and modules adapted to carry out the method.