2025-01-18
10kV Cable Fault Detection
1. Basic situation on site
（1）The cable is cross-linked polyethylene 10kV.
（2）The three phases ABC at both ends of the cable have been removed.
2.Instruments used
（1） Insulation resistance tester (XHMR-2500V).
（2） Cable fault pre-locator (XHGG502A).
（3） Cable fault pinpointer (XHDD503E).
（4） High voltage pulse generator (XHHV535-4Z).
（5） Cable fault comprehenvise tester (XHGX507).
3.Testing process
（1） Test and discharge the cable, remove the cable ends at both ends and keep them suspended.
（2）Use an insulation resistance tester with a voltage of 2500V to measure the three-phase to ground and between phases of the cable to determine that the insulation of phase C to ground is 0.02MΩ.
4.Cable length
After using the insulation resistance tester to measure the faulty phase, use the cable fault tester XHGG502A to perform three-phase to ground and phase-to-phase measurements on the cable. After turning on the device, select the test page mode: pulse, select the medium speed corresponding to the cable material, and select the length (if you are not sure, you can temporarily not select it, wait for the waveform to appear and then make adjustments). After the selection is completed, click "Sampling". After the waveform is completed, click Hold, and click Automatic Measurement.
The AB phase-to-ground test waveform shows that the total length of the cable is 473 meters, and a rough measurement of phase C shows a circuit breaker fault.
Automatic measurement is a unique test function of the cable fault pre-locator XHGG502A. There is no need for manual waveform analysis. The cable fault tester automatically analyzes the fault waveform, which is accurate, intelligent and efficient.
Low voltage pulse method full length waveform
The marked cable length is 470 meters and the test length is 473 meters.
5. Rough fault distance
The low-voltage pulse method measures the total length, but cannot measure the fault distance. The high-voltage pulse generator XHHV535-4Z is used to pulse the faulty cable to break down the fault point. When the voltage rises to 15kV, a flashover discharge is formed at the fault point, and the fault distance is 377 meters.
Roughly measuring the low-voltage pulse waveform, the total length measured by phase C is different from that measured by AB. It can be preliminarily determined that a circuit breaker fault occurred at 377 meters.
Rough measurement of low voltage pulse waveform
6.Fault finding and precise positioning
When accurately locating the fault point, pay attention to understanding the direction of the cable path. Use the cable fault pinpointer XHDD503E to locate the point directly above the cable in the range before and after the distance measurement. Move the probe no more than one meter each time. The signal is the largest directly above the cable fault point, indicating that the fault point has been found. Excavate to confirm the fault location.
7.Fault Test Summary
（1） When determining the location, you must know the cable path accurately. Once the location is deviated, the location meter will not receive any signal, so you must find the cable path before testing.
（2） After determining, wait for excavation and increase the voltage of the faulty cable at any time. (In case the sheath of the nearby cable is damaged, other cables are regarded as faulty cables. Only after confirmation can the next step be carried out.)
