What are the high-resistance faults in cable?
High-resistance faults in cables refer to faults where the insulation layer of the cable is damaged, and the direct current resistance at the fault point is much higher than the characteristic impedance of the cable itself. The resistance value typically ranges from several thousand ohms to several megohms. Such faults are not as easy to detect as low-resistance short circuits or grounding faults. Common causes include:
1. The insulation layer of the cable has aged and cracked over time, resulting in a decline in local insulation performance.
2. Minor external force damage (such as compression or puncture) that does not completely break through but forms a high-resistance path.
3. Defects in the manufacturing process of the cable joint lead to poor contact after long-term operation.
4. Moisture intrusion into the insulation layer forms a high-resistance leakage path.
How to detect the high-resistance faults of cable?
For high-resistance faults, we use the high-voltage flashover method to test. For leaky high-resistance faults, a high-voltage pulse signal source is used to make the cable fault point flashover and discharge, so that the fault point generates a reflected signal, and the fault reflected wave is detected at the test end. The high-resistance flashover fault uses the DC high-voltage power supply to cause the fault point of the cable to flashover and discharge, so that the fault point generates a reflected signal, and the fault reflected wave is detected at the test end.