Recently, Xi'an Xuzhihui Electromechanical Technology Co., Ltd. successfully completed a repair task for a 35kV cable flashover fault. The cable, which had been in operation for 5 years and was approximately 2000 meters long, connected a power distribution room at one end and was mounted on a pole at the other. Fault recording showed an anomaly in phase B, affecting the reliability of power supply in the area, prompting the customer to urgently request repairs.
During the initial fault detection, the technical team used an XHMR-5000V insulation resistance tester to perform a relative-to-ground insulation test on phase B. At 5000V, the insulation resistance was measured at 2.5 GΩ, which, based on conventional data, suggested good insulation performance. However, drawing on their extensive operation and maintenance experience, the technicians anticipated a potential deep-seated hidden problem. They then used an XHYB-5/50 test transformer and an XHCC-6/40 pulse energy storage capacitor to build a test system and conduct a DC withstand voltage test. When the voltage rose to 40kV, a flashover breakdown discharge occurred in phase B, ultimately confirming the fault as a "flashover high-resistance fault"—a type of fault that exhibits normal insulation performance under low voltage but cannot withstand the actual operating voltage, making it highly insidious.
To accurately locate the fault point, the technical team adopted a "three-step" detection strategy: First, they used the low-voltage pulse method of the XHGG502 cable fault tester to verify the entire length of the cable, confirming that the actual length matched the documented 2000 meters, establishing a baseline for subsequent distance measurements; then, they used the high-voltage flashover method of the same instrument to successfully capture the waveform at the moment of breakdown discharge at the fault point, roughly measuring the fault point distance at 1629.8 meters; finally, they used the XHGX507C pipeline locator to determine the exact route of the buried cable, and then used the XHDD503E cable fault locator for acoustic-magnetic synchronous detection, precisely locating the fault signal at 1630 meters.
On-site excavation confirmed that the fault point was at the cable's intermediate joint, perfectly matching the location results, and the repair work was completed efficiently. Regarding this fault resolution, the Xi'an Xuzhihui technical team summarized three key lessons learned: First, the detection method must accurately match the fault type; the high-voltage flashover method is an efficient and reliable choice for troubleshooting this type of high-voltage breakdown fault. Second, cable joints that have been in operation for more than 5 years are susceptible to the effects of electric fields, heat, and moisture, and should be a focus of daily maintenance. Third, in complex environments such as direct burial and multi-cable parallel installations, confirming the cable path before fault location can significantly improve troubleshooting efficiency.
As a professional enterprise in the field of power testing and experimental equipment, Xi'an Xuzhihui has always taken "safeguarding the reliable operation of the power system" as its mission. With its professional testing equipment and technical team, it provides precise solutions for various power cable faults. The efficient completion of this emergency repair once again demonstrates its technical strength and practical experience in the field of power fault detection. For related technical issues, you can contact the company through its official website www.xzhjdkj.com or by calling 400-029-0829 for support.
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