Reliability Research Of ECT Based On Fault Tree And Monte Carlo Method

With the development of modern power system technology,a series of problems such as magnetic saturation,large volume and difficult insulation of traditional electromagnetic current transformers are becoming more and more obvious,which can not fully meet the development needs of digital and intelligent power system.To solve this problem,electronic current transformers(ECT)have gradually replaced the traditional electromagnetic current transformers.At present,the number of LPCT and FOCT which are put into operation in China are small,and the engineering verification data is limited.There is still a big gap of reliability level between the electronic current transformers and traditional electromagnetic current transformers.There is still lack of theoretical support and analysis to prove if the equipments reliability can meet the needs of power development.Thus it is very important to analyze the reliability of LPCT and FOCT in power system.For the reliability of electronic current transformers,the main research contents of this paper are as follows:(1)The constituent unit of LPCT and FOCT are determined,and the main components of each unit are determined.The fault location and fault mode of LPCT and FOCT are identified,and the fault trees of the two devices are established.The fault trees are analyzed by downward method,and the minimum cut sets of two kinds of equipments are obtained.Then the cut sets are classified into first-order cut sets and second-order cut sets and the results are analyzed.So far,the qualitative analysis of reliability of electronic current transformers are completed.(2)The failure rate prediction models and their failure parameters of LPCT and FOCT are determined by the 《Reliability Prediction Manual of Electronic Equipment》.The reliability analysis of LPCT and FOCT are carried out by Monte Carlo analysis method.Then the curves of reliability and failure probability with time and the average life of the two kinds of equipments are obtained.The accuracy of the Monte Carlo analysis method to calculate the average life of the equipments are verified by using the component counting method,so as to complete the quantitative analysis of the equipments reliability.(3)According to the calculated failure rate data of the two kinds of equipments,the components with higher failure rate of LPCT and FOCT have been improved.It is found that the average life and reliability of each equipment are improved,and the failure probability of each equipment is reduced within the range of average life,that is,the reliability of each equipment is improved compared with that before.