Neutral corrosion condition survey-mitigating induced voltage effects

摘要

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. A further enhancement to this method of use and system is addition of a current balance test and a current partition test. The current balance test determines the ratio of the test current in/out of neutral conductor under test, thereby providing an indication of the electrical continuity or breaks of the neutral conductor. The current partition test determines the ratio of the test current in the neutral conductor to the generator test current, thereby providing a relative indication of the amount of test current actually passing through the neutral conductor under test.