Basic And Application Research On Fault Location Of Extra High Voltage Transmission Line

Quick and accurate localization of faults is the basic task of fault location as well as an important research subject in power system relay protection.Many domestic and foreign experts and scholars in this field had studied a number of fault location methods,which can accurately locate the fault point by using data before and after fault of one or two terminals.With technological development,many IEDs available today are capable of recording,executing analysis automatically and communicating results to different locations.However,the fault location result is often not satisfied in many of more challenging fault locating applications,including: distributed capacitance,fault resistance,system impedance,load current,Error of line parameter,line structure and so on.There are still quite a lot to be improved in theory and practice.The paper is intended to investigate better fault location,by providing input on new theory,new technology and techniques.Firstly,the study and investigation of fault location technology is done.A variety of methods and application of fault locators are analyzed.The theory of existing fault location approaches /technologies,key technologies,advantages and disadvantages are analyzed.A number of fault locators are also researched including the application and feeder back of them.Meanwhile,a prospective study of the future development and application of traveling wave based method and impedance based method are also conducted.Secondly,considering all the methods and fault locators have been researched,further study and simulation on the promising fault location based on two-terminal voltage and current is done.The basic fault location algorithm is analyzed and further extended and applied for single loop line but also parallel line,T line and quadrangular structure grid.Form analysis and simulation result we can find this method is both accurate and robust.Admittedly,this method need more data transmission from remote terminal,with the development of smart grid,communication will not be a problem in the future,so that it has a more brilliant future in practical use.Thirdly,as the HV transmission line is often equipped with current differential protection,thus the contralateral current can be obtained at local terminal by using communication channel.Meanwhile,considering the limitation of communication channel,an accurate fault location method using local voltage,current and contralateral current is put forward.The algorithm is based on the distributed parameters model and the distance measuring equation is constructed by fault boundary conditions.The effects of fault resistance,system impedance,distributed capacitance,data synchronization and false root problem are eliminated.The simulation result of RTDS indicates that the algorithm has high accuracy and stability.Fourthly,the method using voltage and current of one end and contralateral current is further extended and applied for T-line.The derivation of distance measuring function is similar but false root may occur on sound line when fault occurred close to T node with high fault resistance.The false root discrimination method is proposed by the difference of currents of contralateral terminals calculated by fault location result and measured currents.The effects of fault resistance,system impedance distributed capacitance are eliminated.The simulation result of PSACD indicates that the algorithm has high accuracy and stability.