Research On Fault Location Of Distribution Line Based On High Precision Wave Recording

Distribution lines connect users,and its operation state is of great significance to the society.With the growth of power load and the beautification effect of the city,a large number of cables are used for power supply in the urban area.In Beijing,Shanghai,Guangzhou and other cities,the medium voltage distribution network has gradually adopted the neutral point small resistance grounding system.The characteristic quantity of small resistance grounding system after fault is obvious,which provides more abundant and effective electrical quantity information for fault location.And with the development of distribution automation,micro synchronous phasor measurement device is widely used(μ With the wide application of PMU,high precision synchronous voltage and current data acquisition and wave recording are available.Based on this,based on the high-precision recording data of distribution lines,this paper studies the single-phase grounding fault in the neutral point small resistance grounding system(1)This paper analyzes the error characteristics of the traditional impedance fault location method based on the zero sequence current compensation principle and the node impedance matrix fault location method.Aiming at the unknown load at the end of the distribution line,this paper proposes a solution to obtain the load impedance by using the voltage and current at the bus side before the fault.(2)In view of the situation that the distribution line has many branches and the branch load is unknown,the branch and load are modeled as a constant impedance model.The nonlinear equations are established by using the two terminal electrical quantities before the fault.The equivalent impedance of the branch can be obtained by L-M algorithm,and then the load impedance can be obtained.The fault distance can be calculated by using the principle of equal voltage from two terminals to the fault point in the trunk line;In each branch line,the method based on node impedance matrix is used for fault location.(3)When the parameters of a single distribution line are unknown,taking the positive sequence,zero sequence parameters and fault distance of the line as unknowns,based on high-precision two terminal synchronous measurement of electrical information,nonlinear equations are established to identify the line parameters and solve the fault distance;Furthermore,the constraint equation is added to the fault location method for the single branch transmission line with unknown parameters.The method proposed in this paper can effectively solve the multi branch single-phase grounding fault location problem of distribution line in neutral point small resistance grounding system and the fault location problem when the line parameters are unknown.