Abstract:The application of big data technology can greatly optimize the reliability management for medium voltage power supply of distribution network. The concept of big data and the analysis methods of big data technology in the field of electric power are introduced. A reliability management system for medium voltage power supply based on big data is developed: it can get the information of power supply reliability for urban power grid and rural power grid. It can analyze the repeated blackouts rate in one area ( including repeated blackouts on lines and repeated blackouts of transformer districts) and the planned blackouts, and can provide the quality services such as fault repair efficiency analysis for distribution network and power outage loss estimation. The analysis results of the proposed system can provide a reference for the staff to improve the reliability of medium voltage power supply.