In the vast wind farm of Inner Mongolia, a 26-kilometer-long high-voltage cable had malfunctioned. Previously, a team had attempted to locate the fault by excavating at a point 3 kilometers away, based on their experience, but found nothing. Where exactly was the fault located? Was it necessary to blindly excavate for tens of kilometers? When the Xi'an Xuzhihui technical team arrived on site, they faced not only a technical challenge but also a test of trust regarding the importance of "precision."
Insulation test: Using the XHMR-5000V insulation resistance tester, an insulation test was performed on phase B relative to ground. At 5000V, the resistance was 0.09 MΩ (at 500V), while all other measurements were above GΩ. The conclusion is that phase B has a high-resistance leakage fault to ground.
Total length verification: First, using the XHGG502 cable fault tester, the total length of the cable was measured to be approximately 26008.7 meters using the low-voltage pulse method, which is consistent with the documented length of 26 kilometers, establishing an accurate baseline for subsequent distance measurements.
Withstanding voltage test: Based on our experience, we suspected there might be underlying hidden defects. We then used the XHYB-5/50 test transformer and XHCC-6/40 pulse energy storage capacitor to conduct a DC withstand voltage test. When the voltage rose to 26kV, the fault point in phase B was punctured. Using the high-voltage flashover method of the XHGG502 cable fault tester, at the moment the voltage was applied to 33kV and the fault point discharged, the instrument successfully captured the discharge waveform, and the approximate distance to the fault point was measured to be around 3101.3 meters.
We took the XHDD503C cable fault locator to a location near 3101.3 meters, but could not hear the discharge sound at the fault point. We then connected two 40/6 capacitors in parallel and increased the voltage to approximately 30kV. We were then able to hear the discharge sound. After excavation, the fault point was confirmed to be at 3100 meters. The function of the capacitor: In high-voltage flashover testing, the pulse capacitor is an energy storage element. It stores electrical energy and then releases it at the moment of breakdown at the fault point, generating a powerful impulse discharge current. The principle of parallel connection: When capacitors are connected in parallel, the total capacitance increases (C_total = C1 + C2), but the working voltage remains unchanged. This results in a significant increase in the total stored energy (E = 1/2 * C * U²). At the same voltage, a larger capacitance can store and release more electrical energy. During discharge, the instantaneous impulse current is larger, and the arc generated at the fault point is more intense and expands more rapidly, thus exciting stronger mechanical vibrations and sound waves.
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