| In China,resonant grounded and ungrounded neutrals are widely used in distribution system.When single phase earth fault occurs,it is difficult to locate the fault position due to weak current.Furthermore,the traditional fault location methods mostly can’t be automatically positioning,and the effects of actual practice are bad.Therefore,it is significant to find a fast and automatical fault location scheme for improving the power supply reliability and ensureing the safety of power grid operation.In this paper,firstly,the elementary theory of traveling wave on transmission line was elaborated,and the traveling-wave modulus of initial wavefront was analyzed,and the aerial mode of traveling wave used by the traveling wave location method has been proposed.Then,the transfer characteristics of traveling wave in impedance discontinuities was studied.After that,a new method using the transformer to catch traveling waves has been proposed to solve the difficulty of the traveling-wave extraction.There exists the mapping relationships between fault location and travelling wave which is recorded by the fault postion device.A traveling wave location method for distribution networks based on wave correlation analysis has been put forward creatively,which explored a new idea for fault location in distribution network.In this method,simulative fault positions was set at a certain interval in distribution networks.When the fault happened in simulative fault point,the stand traveling-wave signal array are recorded by the positioning device which was mounted in distribution network,then stored in an elaborated database.While the fault actually occurred,the traveling-wave signal array are recorded by the positioning device.Finally,the correlation coefficients between the the fault traveling-wave array and the standard traveling-wave array was calculated,and the fault position was identifed by compareing the size.The fault position section is between the two positions where correlation coefficients are most.On this basis,the fault position could be accurately located,through identifying to the reflective wave at the fault point,and combined with the traditional single-ended traveling wave location theory in time domain.Moreover,a whole equipment of distribution fault location system based on traveling wave was provided,including the circuit of the superfast acquisition device and the software of fault location.Using the electromagnetic transient simulation software ATP,some distribution network simulation models have been established for the research of traveling wave method of fault location.Many simulation results demonstrate the practicality and efficiency of the proposed method,which can improve the accuracy and reliability of fault location,and the single-ended traveling wave location method is not affected by fault initial phase angles,fault resistances and fault types,without recurring to synchronous sampling and tuning circuit structure,length and velocity parameters.This algorithm has the advantages of fewer operation,so that it is very valuable.The fault location system was provided in the paper,which can realize the fault accurate positioning in distribution network. |
