Font Size: a A A

Research On Single-phase Earth Fault Location Method Using Transient Signal In Distribution Network

Posted on:2019-07-14Degree:MasterType:Thesis
Country:ChinaCandidate:Z Z GeFull Text:PDF
GTID:2382330545999263Subject:Engineering
Abstract/Summary:PDF Full Text Request
Distribution network is the crucial part to ensure power supply reliability due to direct connection to the power users.The distribution network has complex circuit structure,numerous nodes,and a variety of operating environments.The probability of single-phase earth fault occurrence in distribution network is very high.In order to avoid line tripping and power failure immediately after a single-phase earth fault,the neutral point of the medium-voltage distribution network is widely used ungrounded and arc-suppressed coil grounding.When a single-phase earth fault occurs,the fault current is small,the system voltage basically remains three-phase symmetrical,and it can supply power to the user in a short period of time.Some transient earth faults can be automatically restored without power outage processing and have high power reliability.However,overvoltage may occur during the duration of single-phase earth fault.Accelerated insulation deterioration or even insulation breakdown will cause single-phase earth fault to be converted into phase-to-phase short circuit,causing the entire line power failure.If the wire breaks down on the ground,there is still a hidden danger of human electric shock.It is necessary to quickly determine the location of the earth fault so that measures can be taken to isolate the fault in time.Because of the small earth fault current and compensation of arc suppression coil,it is very difficult to accurately locate the fault point of the distribution network.It is a crucial technical problem that needs to be solved urgently in the field of distribution network.Based on the in-depth analysis of the transient signal characteristics of single-phase earth fault in distribution networks,this paper studies the single-phase earth fault location methods using fault transient signals.The main research work and achievements are as follows:(1)A fault location method by comparing transient zero-mode current frequency is proposed.The distribution law of transient zero-mode current in single-phase grounding fault is analyzed.The fault location is realized by using the characteristic that the frequency of the transient zero-mode current on the same side of the fault point is similar and the frequency difference between the transient zero-mode currents on both sides of the fault point is large.A simplified method for the calculation of transient zero-mode current frequency is proposed,which can effectively reduce the computational cost for solving the transient frequency and facilitate the engineering application.(2)A fault location method by calculating the slope distance of the transient zero-mode current waveform is proposed.Based on the similarity of transient zero-mode currents on the same side of the fault point and the low similarity of transient zero-mode currents on both sides of the fault point,the slope distance method was firstly introduced to measure the similarity of the transient zero-mode current waveform and define the waveform.When the slopes of the transient zero-mode current waveforms of two adjacent detection points are greater than the threshold value,the two zero-mode current waveforms are considered to be not similar.The line between the two points is the fault section.Compared with the calculation of transient zero-mode current correlation coefficient,this method is more fault-tolerant and requires less time synchronization accuracy between detection points,which is convenient for on-site implementation.(3)The proposed location methods are verified by using digital simulation and actual fault data.The Real Time Digital Simulator(RTDS)is used to build a typical distribution network model and obtain simulation data.The MATLAB software is applied for data analysis.The two proposed methods are further verified by using actual field fault recording data.The verification results show that the proposed methods can effectively locate the earth fault section.The two methods proposed in this paper using transient signal location method are not affected by the arc suppression coil.They only need to acquire the transient zero-mode current signal,which is easy to implement in the field.The simplified frequency calculation can be used in location method comparing transient zero-mode current frequency.The detection terminal can only upload the frequency value,and the communication data volume is very small.There is only a certain requirement for the sampling frequency of the detection terminal.The method for calculating the slope distance of the transient zero-mode current waveform requires uploading the slope data of zero-mode current,with a smaller communication data volume.This method requires lower sampling frequency,lower time synchronization precision and calculation capability,and with wide applicability.The correctness and effectiveness of location methods proposed in this paper are verified by digital simulation and actual fault data.
Keywords/Search Tags:Single-phase earth fault, Fault location, Transient zero-mode current frequency, Slope distance, RTDS
PDF Full Text Request
Related items