Abstract: A method of use and system for determining the longitudinal active resistance of a neutral conductor of an underground electrical cable, while the electrical cable remains in service. The method is conducted by applying a selective frequency test current signal to the neutral conductor of the underground cable connected between a pair of grounded structures, e.g., power transformers, from a test signal generator that is connected across the neutral conductor using first and second bifilar winding signal-voltage cables. The method utilizes indirect voltage determination to obtain the voltage drop across the neutral conductor while mitigating induced voltage effects which occur when direct voltage measurement is used. A plurality of selective frequency test current signals are used to obtain a plurality of longitudinal active resistance values. Any conventional extrapolation method is then used to obtain a longitudinal active resistance value at 0 Hz.

Abstract: A system and method for testing underground electric cables, while in service, for active corrosion and degree of neutral loss. The method is conducted by applying a non-harmonic selected frequency signal to the neutral(s) of the underground cable connecting a pair of structures, e.g., power transformers, from a variable frequency generator of the system. The test is conducted by a surveyor wearing foot electrodes which contact the earth as the surveyor walks along the earth over the cable in close interval steps. At each step, direct current (DC) potentials are monitored by a voltmeter between a copper-copper sulfate electrode carried by the surveyor and brought into contact with the ground at each step and the transformer ground. The potential of the gradients between the foot electrodes at the selective frequency and at the native alternating current (AC) is also measured by the voltmeter. These measurements are recorded at a stationary location on a digital data logger and/or computer.