Power Cable Fault Location Method
Fault location method of power cable: Aiming at the problem that it is more difficult to determine the fault location of buried power cable than overhead line, this paper selects a representative example of fault location process of 10 kV cable in case of high resistance fault, and introduces the method of locating and locating the fault point by using secondary pulse method according to the fault nature. For the high resistance fault during cable operation, first consult the relevant data of the cable and master the detailed information of the cable; Use multimeter and insulation resistance meter to judge the cable fault type, and determine the corresponding test method according to the fault type; Use the fault tester to test the length of the cable, check whether the test results are consistent with the data, and preliminarily determine the distance of the fault point; Finally, the secondary pulse method is used to accurately locate the fault point, find out the fault point, peel off the cable and find out the cause of the cable fault, so as to take corresponding preventive measures. This method is easy to master, especially for short-distance faults, the test waveform is easier to analyze, and the fault distance can be determined quickly, which makes the cable test more efficient and the fixed-point positioning time shorter. Power cable faults are complex and diverse, which can be divided into open faults and closed faults according to fault surface phenomena; According to the grounding phenomenon, it is divided into grounding fault, phase to phase fault and mixed fault; According to the fault location, it is divided into joint fault and cable body fault; According to the nature of resistance, it is divided into broken line fault, mixed line fault and mixed fault. Among them, mixed line fault is divided into low resistance fault, high resistance fault and flashover fault. 1. Fault detection methods for different cable faults, the common detection methods include low voltage pulse method, pulse current method, secondary pulse method, bridge method, pulse voltage method, etc. . This paper only introduces the three commonly used detection methods. 2. Low voltage pulse method low voltage pulse method is suitable for detecting low resistance fault (short circuit fault with fault resistance less than 200 & omega;) and open circuit fault. It can also be used to measure the length of cable and the propagation speed of electromagnetic wave in cable, and distinguish the middle head, T-joint and terminal head of cable. 3. Pulse current method pulse current method generally includes impulse flash method and direct flash method. The linear current coupler is used to collect the current traveling wave signal in the cable and generate the fault test waveform, so as to judge the fault condition and measure the distance between fault points through the waveform. The direct flash method is used to detect flashover breakdown faults, that is, the resistance at the fault point is very high, and flashover breakdown faults will occur when the voltage is raised to a certain value with high-voltage test equipment. The impulse flashover method is also suitable for testing most flashover faults. Because the waveform of the direct flashover method is relatively simple and it is easy to obtain more accurate results, the direct flashover method should be used as much as possible. 4. Secondary pulse method with the cooperation of high voltage signal generator and secondary pulse signal coupler, the secondary pulse method can be used to measure the fault distance of high resistance and flashover faults. The waveform measured by this method is simpler and easy to identify.