Magneto-optical current transformers (MOCT) are important primary equipment for ensuring the normal, safe and reliable operation of the power system. Therefore, magneto-optical current transformers must have very high operational reliability. MOCT have been widely used in smart grid construction because of their technical advantages that traditional current transformers cannot match. However, magneto-optical current transformers can ultimately replace traditional current transformers, depending on their long-term reliability. At present, domestic and foreign scholars have carried out more research on the reliability research of magneto-optical current transformers, and have also obtained some research results, which promoted the application and development of magneto-optical current transformers.
　　Magneto-optical current transformers are considered to be the most ideal current transformers. Because their system structure not only contains electronic components but also many optical components, its reliability involves a wide range of factors, complex influencing factors and numerous failure modes. Therefore, the reliability research and literature on magneto-optical current transformers are still relatively few, especially the research on the overall reliability of magneto-optical current transformers is hardly involved. Therefore, it is of great theoretical and practical significance to evaluate and analyze the reliability of magneto-optical current transformers.
　　This article provides data on the applied reliability assessment schemes, evaluates the MOCT reliability indicators, contains the research results, uses the methods and results of the conclusions, and has a relationship to the study of the magneto-optical current transformer.
　　This article includes three parts, as reliability analysis, reliability prediction and reliability simulation. First,in the reliability analysis we consider a fault tree,which used to conduct a qualitative analysis of reliability to find the weak link(minimum cut set)of the magneto-optical current transformer. To assess the reliability prediction,the reliability of each component of the module, and each modules reliability of the whole system had calculated.In the last part, the calculation of the reliability and the average life expectancy had carried out by Monte-Carlo method, which is used to simulate reliability.
　　The MOCT has 92.6% of the minimum first-order cut set. The number of minimum sets should be minimized during the design process of the MOCT. After about 127,500 hours, reliability drops to 0.5, and the average life expectancy is about 21.66 years. The MOCT has the highest probability of failure at the initial stage of operation. As the working time increases, the probability of deviation will gradually decrease.