Research Of Small Current Fault Line Selection Technology In Digital Substation

In recent years,with the electric power system reform, the electricity power grid has been developing very rapidly. With the help of computer technology and communication network technology development, substation automation technology has been in a new stage. Digital substation has been a hot concept for several years, and gradually more and more digital substations are being built. In a digital substation, the analogue and binary inputs from the primary side and the control out from the secondary side are very different from that of a traditional substation automation system. The medium, mode and final accuracy of the data transmission are all improved very much. At Present, there have been numerous operating digital substations both in China and other countries. The new-style protection relays, monitoring and control devices and IEDs have entered the stage of practical application at the same time. The low current grounding is widely used in 3-66kV electric power grids in China. More than 80% of the earth faults are caused by single-phase grounding. At present, many principles and algorithms have been used in business, however, the correctness rate is still not high enough and can only meet the requirements of the traditional substation. Then, the new-type device for single-phase earth fault line selection to be used in a digital substation is inevitable also. A digital substation has more advantages than a traditional substation so that higher correctness rat for earth fault line selection can be achieved more easily. This paper will describe the realization of selecting the single phase earth fault line in a digital substation. The paper proposed fault line selection device based on a small analog distributed hardware and software based on the above, and established of the IED model, and the feasibility is verified by the actual site.