Study On High Frequency And High Voltage Power Supply And Its Application For Locating Cable Fault

High voltage power supply, an indispensable equipment for the high resistive fault detection of power cable. The frequency of traditional high voltage power supply is 50 Hz, which leads to large magnetic core size of power frequency transformer, low efficiency, high temperature rise, and too many primary and secondary turns. Therefore, the volume of power supply is large, bulky, and inconvenient to transport and move. In this paper, a small volume, light weight, high efficiency power supply is developed, whose operation frequency is much higher than 50 Hz.In this paper, the high frequency and high voltage(HFHV) power supply is designed based on the basic principle of switching mode power supply and its topology structure. The bridge rectifier circuit is selected to realize the power frequency rectification. Using the full bridge inverter circuit to complete the conversion of DC votage to high frequency square wave votage. The high frequency transformer takes the place of the traditional power frequency transformer to boost the main circuit. At last, the HFHV pulses is rectified by the voltage doubling rectifier circuit, and DC high voltage is obtained. The high voltage power supply generates sharp pulses by charging the capacitor in parallel, and then discharging through the gap switch. The discharge frequency is about 0.5 ~ 1Hz, which can meet the requirements of the cable fault detection.After the simulation analysis of the power supply, the circuit parameters calculation and the selection of components, a HFHV power supply for cable fault detection was developed. The main technical parameters are, output voltage: 0-35 kV, maximum current: 35 mA, the maximum output power is about 3.5kW, size: 35cm×25cm×32cm, weight: 10.5kg. It means the miniaturization and lightweight design of the power supply is fulfilled. In addition, the cable fault simulation test platform is built, and the high frequency and high voltage power supply is used to test the impulse flashover discharge of the fault cable. The results show that the power supply can effectively make the cable fault impulse flashover discharge stably.More over, this paper makes a detailed description of the general steps of the cable fault detection. The comparison and analysis of various test methods of the cable fault distance provides the theoretical guidance. At last, the power supply is used locate the 200 m fault cable in the field. Based on the traveling wave method pulse current method and the cable fault location instrument, the accurate location of the fault of the cable is found, the test results is 175.4m, which is within the scope of the test error comparing to the fault point defined as 170 m. and the fault point is defined as 170 m through the final accurate fixed point, which is within the scope of the test error. The whole test process shows that the selfmade HFHV power supply runs well. At the same time, the test waveform is analyzed, and the basis of the waveform recognition is presented, which is of significance for the practical application.