Research On Leakage Protection Method Based On Additional Low Frequency Power

Leakage fault is one of the main faults of coal mine underground low-voltage power grid,accounting for 70% of the total number of faults.It is also the reason that seriously affects the mine's safe power supply and personal safety.Therefore,a reliable leakage protection system is a necessary condition for the safe power supply of the underground low-voltage power grid and the normal operation of the production.The leakage protection technology of coal mine underground low-voltage power grid has not developed for a long time in China,but it still plays a positive role.With the rapid development of computer networks and electronic technologies,leakage protection devices with comprehensive principles and multiple functions are gradually being applied in practice.In this paper,the relationship between the leakage fault model of underground low-voltage power grid and the zero-sequence current and voltage of each branch in fault is analyzed in detail,and the principle of several common leakage protection methods is introduced.Then,a leakage protection method based on additional low-frequency power supply is proposed,which is to monitor the insulation level of the cable by adding a low-frequency signal to the grid and then collecting the low-frequency voltage and current.The final simulation analysis shows that the method can not only achieve the purpose of monitoring the cable insulation level,but also realize the line selection function of the fault branch.The simulation of this paper is completed by SIMULINK module in MATLAB.The simulation analysis of the additional low-frequency power supply method shows that the theoretical analysis results are correct.The method of measuring the insulation parameters with additional low-frequency power supply can indeed monitor the cable insulation level and the error is better.small.In addition,the leakage protection method has strong adaptability and can be applied to various types of power grids,and can effectively solve the problem of low sensitivity and poor reliability of some grid leakage protection systems.According to the simulation results of this paper,it is also known that the cable distribution capacitance and the power frequency also have an impact on the monitoring accuracy.Finally,the leakage protection device is designed based on the additional low-frequency power supply method,including the design of the system hardware and software.The main circuit of the hardware is introduced to analyze the working flow of the device and the system software flow chart is given.Several anti-interference measures are also introduced.