Partial discharges in low-voltage cables

A novel method, utilizing partial discharges, is presented which has the potential for locating breaches in the insulation of in situ, low-voltage, multiconductor cables. The measurement technique is intended for use in situ on 600-V-class nuclear power plant cables, and so representative cable types were used in the experiments described: shielded cables, unshielded multiconductor cables, and unshielded single-conductor cables. It is shown that the proposed method can differentiate between signals emanating at incipient defect sites and the background of partial discharges occurring over the length of the cable. In order to induce partial discharges, the test voltage must clearly be raised above the inception voltage. Depending on the cable structure, this test voltage will be on the order of a few thousand volts, a subject of possible concern, but not a fatal limitation for a test method offering definite identification of defects that could become fault locations