Research On Fault Location Method Of Medium And High Voltage Distribution Network With Small Current

With the rapid development of national economy,power consumption is increasing day by day.Because of the vast area and complex environment,distribution lines are prone to all kinds of short-circuit faults.The short circuit fault of the distribution line will directly affect the power supply reliability of the power system.At present,many places in our country still find the fault point by the way of manual inspection,which wastes not only manpower but also material resources.Therefore,it is very important to study the method of fault location in distribution network.In this thesis,the related concepts and characteristics of distribution network and low-current grounding system are introduced,and the present research status of fault location technology in distribution network system is analyzed,and then the related theory of fault location is introduced.The fault location method of distribution network is studied.The main research contents of this thesis are as follows:(1)Based on the traditional two-terminal fault location method.The fault model of distribution network is modified by considering the influence of line admittance on location accuracy,and the line structure is equivalent to ? type.Then the total admittance of the line is calculated according to the line before the fault.After that,the positive sequence voltage and current phasor matrix is obtained by using the voltage and current phasor after the fault.Finally the fault coefficient matrix determined by the fault type and the impedance parameters of the distribution line are combined to establish the location function so as to calculate the fault distance.The simulation results show that the method is effective and the accuracy of fault location is improved.(2)Dynamic fault location method based on time-domain.On the basis of two-terminal fault location method,a time-domain based dynamic fault location method for distribution network is studied.The relationship between fault points and fault information of bus side and load side is analyzed,and the time-domain location equation of two monitoring points and fault relative ground voltage is established by combining line parameters,and then the fault transient data of monitoring points are fitted by Prony algorithm.Combined with the time when the fault phase current gets the extreme value,the location algorithm is optimized and the dynamic fault location is realized.Finally,the effectiveness of the method is verified by simulation experiments.The comparison between this method and the two-terminal fault location method based on line admittance shows that the method has good accuracy and stability.