Research On Line Selection Algorithm Of Single-phase Grounding Fault In Mine Power Supply System

This subject is a continuation subject of Shanxi Provincial Fund "Study on the Distribution Law and Prevention Method of Stray Current in Mine Power Supply System"(Project No.:201701D221240),which is proposed to solve the problems of low accuracy and poor reliability of the single-phase grounding fault line selection algorithm in the current mine power supply system in my country.With the rapid development of smart mines in my country,the scale of the mine power supply system has continued to expand,the power supply capacity has increased rapidly,and the corresponding power supply distance has continued to increase,which has significantly increased the probability of single-phase grounding faults.At the same time,under the big goal of intelligent power supply proposed in my country,higher requirements are put forward for the accurate judgment and rapid removal of faulty lines,and the current line selection technology is far from the expected ideal standard.Therefore,it is necessary to explore a single-phase grounding fault line selection method with high accuracy and high reliability,so as to realize the rapid and accurate removal of the fault line of the mine power supply system.It has very important practical significance in ensuring the safe and reliable power supply of coal mines,safe and stable production and operation,and continuously promoting the green and intelligent development of coal mining.This paper takes a typical mine power supply system of a coal mine of Shanxi Coal Group as the research object,the corresponding simulation model is built by uses RTDS(Real Time Digital Simulator),and a single-phase grounding fault line selection method based on CEEMD and autocorrelation threshold denoising is proposed.And the accuracy and reliability of the method are verified by closed-loop experiments.The specific research contents are as follows:Through consulting a large number of literatures and extensive research,the advantages and disadvantages of various single-phase-to-ground fault line selection methods are analyzed and summarized,and an overall research plan is formulated.Taking the mine power supply system with the neutral point indirectly grounded as the research object,through the derivation of the relevant voltage and current formulas before and after the fault and the mechanism analysis of the fault characteristics,the transient and steady state characteristics of the fault are clarified,which provides a theoretical basis for the research of line selection algorithm.A simulation model of a typical mine power supply system was built by using RTDS.On the basis of verifying the accuracy of the model,the influence of different factors on the fault characteristics was simulated and analyzed,revealing the changing law of the zero-sequence current of faulty lines and normal lines,laying a solid theoretical and model basis for the study of line selection algorithms.Aiming at the problem of serious noise interference in the process of single-phase grounding fault feature extraction,the principle of two mainstream denoising algorithms,wavelet packet transform and CEEMD decomposition,is analyzed in detail.On the basis of clarifying their respective advantages and disadvantages,combined with autocorrelation analysis,the two are comprehensively improved,and a denoising algorithm based on CEEMD and autocorrelation threshold is proposed;the denoising effects of these three algorithms on noisy zero-sequence current signals are compared and studied,the superiority of the improved denoising algorithm is verified,and a good data foundation is provided for the subsequent research on line selection methods.Aiming at the problem of poor reliability of line selection in the current mine power supply system where the neutral point is grounded through the arc suppression coil,a single-phase grounding fault line selection method based on CEEMD and autocorrelation threshold denoising is proposed,which realizes the reliable line selection of faults based on the double criterion of amplitude energy and phase.On the basis of the constructed RTDS mine power supply system model,a large number of line selection tests were carried out on different fault conditions such as the grounding resistance of the fault point,the initial phase angle of the fault,and the location of the fault point.The results show the accuracy and reliability of the line selection method.In order to comprehensively verify the line selection effect of this line selection method,a closed-loop test scheme of the single-phase grounding line selection algorithm is designed.Use the real-time simulation function of RTDS to simulate the real fault situation with a high degree of reduction,and provide a data source for the test;select TMS320F28335 DSP as the core of the fault line selection algorithm test device,design the zero-sequence current signal conditioning and acquisition channel,the line selection result output display and feedback channel,and write the line selection algorithm test program,which provides reliable hardware support for closed-loop testing.A large number of closed-loop test results show that the denoising algorithm is real-time and efficient,and the fault line selection is reliable and accurate.An effective line selection algorithm is provided for the single-phase grounding fault of the mine power supply system,and the safety level of the mine power supply is improved.