Currently, the commonly used methods of measuring faults mainly use the size of the resistance to be proportional to the length of the cable, use the bridge principle to measure the resistance between the end of the faulty cable and the fault point, and compare it with the non-faulty phase, and then determine the distance to the fault point .
Capacitance Bridge Method
Use the capacitance bridge to measure the open circuit and disconnection of the cable. When the cable is open circuit, because the DC bridge measurement arm fails to form a DC path, the resistance bridge method will not be able to measure the distance to the fault. Only the capacitance bridge method can be used. And use the high-voltage bridge method to measure the leakage and high-resistance breakdown.
Standing wave method.
According to the principle of microwave transmission line, the standing wave resonance phenomenon of the transmission line is used to test the faulty cable. This method is suitable for measuring low resistance and open circuit faults.
Pulse method.
Use DC high-voltage signal source to directly transmit pulse signals to the faulty core. Use the instrument to receive the signal and position it accurately.
Combining the above method and technology application, 1. First determine the nature of the cable fault, 2. Roughly locate, use the bridge method or the cable fault locator to determine the distance of the fault point in meters. 3. Use DC high voltage signal source to directly transmit pulse signals to the faulty core. 4. Use underground cable tester to accurately locate, and the error will not exceed half a meter.