Research On Segregated Current Differential Protection Based On Optical Fiber Channel For Transmission Lines

With the booming of electric power, more and more EHV & UHV transmissionline will be constructed and put into service. It is crucial for ensuring the safety andstabilization of power grid and going on of the economic construction to switch offthe faulty line rapidly and correctly. The qualities of current differential protection,such as simple theory, rapid action and good dependability, have made it extensivelyused in UHV transmission line as the main protection. At the same time, thedevelopment of technology of optical fiber communication has provided reliablecommunication channels for the differential protection.So it is a perfectchoice for theEHV & UHV transmission line to use the current differential protection based onopticalfiberchannelsasthemainprotection.This paper concentrates on the theory of current differential protection based onopticalfiberchannelsandtheproblemsaboutcommunication.Firstly,thecriterionsofdifferential protection are presented in detail and the influence factors are analyzedwhen the criterions are applied in the EHV transmission line. Secondly, thetechnology of optical fiber communication used for differential protection and therelevant algorithms are discussed, with an emphasis on the data synchronizationmethods of differential protection based on optical fiber channels. The deficiency ofconventional synchronization methods, especially the non-synchronous problemcaused by the non-conforming routes of receiving and transmitting data in the SDHself-healing net, is analyzed. And an amendatory method based on the precise linemodeis proposed.Theanalyses andsimulationresults confirm themethodtobevalidand feasible to keep the sampling data synchronous between two sides of thecommunization channels. At last, a set of software used for the transmission line iscomplied. And the solving programs against the problems of EHV & UHVtransmission line are joined. Combined with the programs of reclosing, a set ofintegratedprotectionsoftwareiscompleted.