latest company case about Xi'an Xu&Hui Electromechanical Technology Co., Ltd. Certifications

In February 2025, a municipal water supply company in Indonesia encountered a power outage caused by a suspected underground cable fault in its 380V low-voltage distribution system. The affected cable supplies critical pumping and treatment equipment, so fast and accurate fault location was essential to minimize production downtime.

XZH TEST field engineers were invited to carry out a complete cable fault detection and location task, from insulation testing and fault nature analysis to rough pre-location, path tracing and precise pinpointing. The whole process was completed efficiently on site with portable XZH TEST instruments.

The cable is a YJV 3×120+2×95 unarmored low-voltage cable with a total labeled length of about 350 meters. Insulation resistance of all phases (A, B, C), the neutral line and the ground line was measured with a 500V electronic megohmmeter, testing both phase-to-phase and phase-to-ground insulation:

Since the A phase, B phase, N line and ground line all showed zero insulation resistance to ground, and the C phase showed 0.08 MΩ to ground with 0.1 MΩ phase-to-phase resistance, the fault was preliminarily judged as a low-resistance phase-to-phase and phase-to-ground fault.

Using the XHGG502 pre-locator with the low-voltage pulse method, the measured full cable length was 348.4 meters (labeled length: 350 meters). The phase-to-phase test of A, B, N and ground lines only showed a reflection at 55.7 meters, which indicated that the A, B, N and ground conductors were broken and grounded near that point, while the C phase insulation was also insufficient.

The cable route was traced with the XHGX507X path tracer. The cable exits from behind the distribution room, is direct-buried along the lawn, and then runs along the inner wall of the plant area.

Based on the rough pre-location result, the fault was expected to be about 55 meters from the test end. The step voltage method of the XHGX507X path tracer was then applied for precise pinpointing: the signal increased sharply at about 50 meters from the test end, and after careful testing the fault point was narrowed down to a range of about 1 meter.

Finally, a high-voltage flashover test was performed with the high-voltage pulse source, and the XHDD503 and XHDD503E pinpointers were used for acoustic-magnetic synchronous pinpointing within the 1-meter range, successfully confirming the exact fault point.

• Low-voltage cable testing should combine multiple methods to prevent misjudgment caused by relying on a single method.
• The step voltage method works very well for unarmored cables with low-resistance ground faults.
• When pinpointing with the pinpointers, the operator must carefully distinguish the sound level difference, which is the key to accurate pinpointing.
• For unarmored cables, high-voltage flashover test waveforms may appear irregular, so the waveform should be used only as a reference.

XZH TEST provides professional cable testing and fault location solutions for power utilities, water supply companies, electrical contractors, industrial facilities and maintenance teams, supporting cable fault pre-location, high-resistance fault location, high-voltage surge testing and precise fault point location.