Research on fault line detection device in digital substation of non-effectively grounded system

There are three different structures between process level and bay level in digital substations below 35kV nowadays; they are IEC61850-9-1 standard, IEC61850-9-2 standard and small analog signal transmission standard. Accounting for the features of three kinds of structures and special requirements of non-effectively grounded system fault line detection device, the design of line detection device is suggested in digital substation with three different structures. Also the advantages, disadvantages, commonality and technical economy of three designs have been deeply analyzed in this article. Considering the characteristic of electronic transformer and the demand for technical economy of system below 35kV, a distributive line-detection design based on small analog signal sampling is proposed in digital substation below 35kV, and this design turns out to be highest commonality and best technical economy.