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Case Study: Precise Location of a 10kV High-Resistance Cable Fault in Turkmenistan

When a high-voltage distribution cable fails, locating the fault point quickly and accurately is critical to restoring power and avoiding unnecessary excavation. In September 2026, XZH TEST carried out an on-site cable fault test for a 10kV cable project in Turkmenistan. By combining low-voltage pulse testing, high-voltage surge (flashover) testing and acoustic-magnetic synchronization, the team moved from a rough fault distance to a precise pinpointing of a high-resistance fault on phase B.

Project Overview

Site Information and Initial Insulation Test

• Laying method: direct burial.
• Cable ends: one end in the distribution room, the other end inside the workshop.
• Initial insulation test: the insulation of phases A and C was normal, while the insulation of phase B measured 0.12 MΩ.

Fault Nature Analysis

Using an electronic megohmmeter on the 2500V range, the team measured the insulation resistance of A-to-ground, B-to-ground, C-to-ground, A-B, B-C and A-C. The values for phase A to ground, phase C to ground and between phases were all normal, whereas phase B to ground measured 0.12 MΩ. The fault was therefore preliminarily judged to be a high-resistance fault of phase B to ground.

Rough Fault Distance Measurement

The rough measurement used the low-voltage pulse method and the high-voltage surge (flashover) method. First, the low-voltage pulse waveform gave the total cable length as 287.2 m. High voltage was then applied for sampling, using the test transformer and capacitor combination to output a high-voltage pulse while the cable fault tester performed a high-voltage flashover test; the preliminary fault distance was found to be about 58 m from the distribution room. Instruments used at this stage included a 5000V insulation megohmmeter, a 5/50 test transformer, a 40/6 capacitor and a 502 main unit.

Precise Fault Location

• Main-insulation fault location was carried out with the acoustic-magnetic synchronization method.
• Cable route finding: the route was clear and the cable was newly laid.
• Precise pinpointing: the voltage was raised to 20 kV until the fault broke down, and the 503 pinpointing instrument was then used directly above the cable within the rough-measurement range; the discharge at the fault point was obvious.

Instruments Used

• 5000V insulation megohmmeter
• 5/50 test transformer and 40/6 capacitor
• XHGG502and XHDD503
• XHGX507C route tracer

Summary

One noteworthy point from this test is that the near-end fault waveform differs somewhat from a conventional high-voltage flashover waveform, so attention is needed when capturing it. By combining low-voltage pulse and high-voltage surge rough measurement with acoustic-magnetic synchronization pinpointing, the high-resistance phase-B fault was located efficiently and with confidence.