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

On July 8, 2025, the XZH TEST field engineering team performed a fault detection and location task on an 800V low-voltage power cable in Thessaloniki, Greece. The cable was a YJV 3×120-800V armored low-voltage cable with the start end connected to the box transformer side and the other end to the photovoltaic panel side. The total cable length was about 700 meters, the route was known, and the cable was laid by direct burial.

• Cable fault locator host 502 for distance measurement;
• High-voltage flashover operation box with test transformer 5/50 and 40/6 capacitor;
• Pinpointing receiver 503 for fault point location.

Using the 500V range of an electronic megger, the insulation resistance of phase A, phase B and phase C was measured respectively, covering all phase-to-phase and phase-to-ground insulation resistances. The results showed that all phase-to-phase and phase-to-ground resistance values were 0.1MΩ.

Initial judgment: high-resistance fault between phases and to ground.

The marked cable length was 720 meters, and the tested length was 716.9 meters, measured by the low-voltage pulse method full-length waveform (phase C).

High-voltage flashover testing was performed from the photovoltaic area side, and the waveform was recorded for analysis. The low-voltage pulse waveform measured the full cable length as about 700 meters. The high-voltage flashover waveform indicated that the fault point was located very close to the transformer side.

Because the fault was a main insulation fault, the audio frequency method was selected for precise location. The cable route was clear, so no route tracing was required. During precise pinpointing at the transformer side, the rough-test waveform was not very obvious, and the fault point was estimated to be very close to the test end, causing the fault sound to overlap with the sound of the instrument itself.

Voltage was then applied from the other end of the cable for retesting. The fault point was finally found underground at the transformer side, 2 meters away from the cable terminal.

This case shows that when the high-voltage flashover waveform cannot be analyzed, the testing team should not blindly start pinpointing. The factors that may cause waveform distortion should be analyzed first, and then the sampling should be repeated for a new pre-judgment before location. Changing the test end proved to be an effective way to obtain a clearer fault point indication.