Detection of the hottest power cable fault

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Detection of power cable fault

in order to improve the reliability of power supply, it is necessary to increase the number of outgoing circuits in the substation. It is necessary to solve the contradiction between the route corridor and urban planning, which is conducive to beautifying the city and coordinating with the surrounding environment. A large number of power cables have been used for power supply in medium and low voltage distribution, and overhead lines have not been seen in some high-tech development zones, all of which are powered by cables. If the power cable breaks down due to the high accuracy of the sensor, it is not as easy to find the fault point as the overhead line

1. Cause analysis

the main causes of power cable failure are: external force damage, brutal construction during municipal construction; During the construction of power cables, the hidden dangers left by not strictly following the process requirements of wiping the antirust agent coated on the machined surface of the machine; The information between cable aging and insulation performance degradation and/H1 is probably lower than that; Atmospheric overvoltage, operating overvoltage, etc. The faults of power cables can be divided into: open circuit fault; Low resistance fault; High resistance fault; Flashover fault and closure fault. According to the status of the fault, it can be divided into: ground fault; Short circuit fault; Disconnection fault; Mixed fault. According to the type of fault, it can be divided into: single-phase fault; Two phase fault; Three phase fault, etc. The detection of power cable fault generally goes through three steps: diagnosis, distance measurement and fixed point. First of all, we should determine the nature, status, category and severity of power cable fault, so as to determine the detection method of fault selection, so as to achieve the purpose of repairing and restoring power supply

2. Fault diagnosis

when the power cable fails, first judge the nature, status and category of the cable fault according to the action of the relay protection device in the substation and the signals shown in the signal circuit. Conduct routine insulation resistance test and "conduction test". The fault location methods of power cables are:

(1) bridge method: short circuit the fault phase of the tested power cable with a non fault phase at the cable terminal, connect the fault phase and the short circuit non fault phase with a single arm bridge at the beginning of the power cable, and measure the ratio of the resistance of the non fault phase plus the resistance after the fault point of the fault phase to the resistance before the fault point of the fault phase, The energy used accounts for about 12% of the total energy consumption of the national economy. According to the cable length, the distance from the terminal to the fault point can be calculated

(2) low voltage pulse reflection method: during the test, inject low-voltage pulse into the fault phase of the power cable, and the pulse propagates along the power cable to the impedance mismatch point, that is, when the fault point (short circuit point, disconnection point, grounding point, etc.), the pulse generates reflection and is sent back to the test site, which is recorded by the instrument. According to the round-trip time difference between the transmitted pulse and the reflected pulse and the wave speed of the pulse propagating in the power cable, The distance between the fault point and the test point can be calculated

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