基于马尔可夫过程的漏电保护器服役状态及其可靠性分析

Service States and Reliability Analysis of Residual Current Device Based on Markov Process

漏电保护器在实际服役过程中可能会发生故障,但诱发其故障暴露的激励条件不具备时,其故障并不能显现出来。针对这一问题,提出一种计及隐藏故障的漏电保护器运行状态划分方法,建立基于马尔可夫过程的运行状态转移模型,实现漏电保护器的实际服役状态准确描述;设计基于蒙特卡洛法的漏电保护器可靠性仿真模型,以漏电故障频次、漏电流大小、保护器可靠性水平和运行时间为主要变量,对无检查和有检查下漏电保护器的状态概率进行仿真分析,确定了保证供电系统可靠性和安全性条件下的最低定期检查频次。该方法适用于不同可靠性水平的漏电保护器的分析与评估,对其定期检查策略的制定具有指导意义。

The residual current Device(RCD)is mainly used to protect power supply lines or electrical equipment leakage faults.During the service of the RCD,it may occur to the reject-operation or the wrong-operation.If the RCD loses its leakage protection function,the lines or equipment have safety hazards,such as personal electric shock or leakage fire.Therefore,it is necessary to study the reliability of RCD.If the RCD fails,its fault state is exposed only when the corresponding excitation condition occurs.The higher the reliability level of RCD,the lower the reject-operation rate and wrong-operation rate.The higher the probability of a normal service state,the lower the probability of a fault state.The reliability block diagram is shown in Fig.A1.The fault state of RCD is divided into two categories:the hidden failure state and the appearing fault state.Therefore,there are five service conditions of RCD:normal service state(State 1),the hidden reject-operation state(State 2),the hidden wrong-operation state(State 3),the appearing reject-operation state(State 4),and the appearing wrong-operation state(State 5).The current moment states corresponding to State 4 and State 5 are necessarily State 2 and State 3,not State 1(previous state).The state at the next moment only relates to the current state,which satisfies the Markov property.Markov process can be used to describe the state transfer of RCD.There are safety hazards when RCD is in the hidden failure state,and it is necessary to eliminate the hidden fault state of RCD by periodic inspection.The state transition diagram of RCD based on periodic inspection is shown in Fig.A2.In general,if the frequency of fault leakage of power supply lines or electrical equipment is low,the RCD in the hidden reject-operation state can be found at a lower periodic inspection frequency.However,the normal leakage of power supply lines or electrical equipment exists permanently,so the probability of the wrong-operation appearance state is still high.If the RCD reliability level is low,self-inspection can be used to achieve a high frequency of periodic inspections,thereby significantly improving the reliability and safety of the power supply system.In different service environments,the frequency of fault leakage and the residual current are different for power supply lines or electrical equipment.So the service environment can be divided into three grades:good,general,and bad.The Poisson distribution describes the frequency of fault leakage,and the Normal distribution describes the amplitude of normal residual current and fault leakage current.Under the same power supply reliability conditions,the higher the reliability level of RCD is,the fewer periodic inspections are required.In addition,a periodic inspection can significantly reduce the frequency of replacing the leakage protector due to apparent failure and can avoid power loss caused by RCD failure.The simulation experiment takes leakage fault frequency,the magnitude of the leakage current,the reliability level of the RCD,and running time as the variables.The probabilities for each running status with and without the inspected RCD are analyzed.The minimum periodic inspection frequency is obtained to ensure the reliability and safety of the power supply system.The simulation results not only explain that the wrong operation is more than the reject-operation of RCD in actual service,but also prove that the service reliability analysis model of RCD based on the Markov process can describe the actual operation of RCD.