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This case study documents a 10 kV power cable fault test carried out in Weinan City in July 2025. The project involved locating a phase-to-ground fault on a direct-buried YJV 3×185 8.7/10 kV cable running between a distribution room and a pole-mounted termination, using a combination of insulation testing, low-voltage pulse and high-voltage flashover TDR methods, cable route tracing and acoustic-magnetic pinpointing.

Cable faults are among the most disruptive events on a distribution network. Fast and accurate location reduces excavation, shortens outage time and lowers repair cost. This case shows how a systematic workflow — insulation diagnosis, length measurement, coarse fault distance and precise pinpointing — resolved a high-resistance fault on a cable where waveform sampling was possible at only one end.

Using an electronic megohmmeter on the 2500 V range, the insulation resistance was measured between A–earth, B–earth, C–earth, A–B, B–C and A–C. The values for phase A to earth, phase C to earth and between phases were all normal, while phase B to earth measured 0.7 MΩ. The fault was therefore initially judged to be a high-resistance fault of phase B to earth.

The marked total length of the cable was 650 m; the measured length was 652.1 m, obtained with the low-voltage pulse method using the full-length waveform.

The coarse fault distance was measured using both the low-voltage pulse method and the high-voltage impulse (flashover) method. First, the low-voltage pulse waveform gave a total cable length of 652.1 m. A high-voltage sample was then taken: a combined high-voltage pulse was output using the test transformer and capacitor, and the cable fault tester carried out a high-voltage flashover test. The preliminary fault distance was about 287.9 m from the tower.

Precise location combined two steps: first, cable route tracing with the pipe / cable locator; and second, main insulation fault pinpointing using the acoustic-magnetic synchronization method. The route was traced with a new-generation cable / pipe locator. The cable was then energized to 20 kV until the fault broke down, after which the 503E was used directly above the cable, within the coarsely measured range, to pinpoint the fault. The discharge at the fault point was clearly evident.