Research On Location And Distance Measurement Method Of Single Phase Grounding Fault Section Of Distribution Hybrid Line

The stable operation of distribution network is related to the development of people’s livelihood.Once the failure occurs,it may cause significant economic losses and even threaten life safety.In the common fault types,single-phase grounding fault accounts for the highest proportion,and with the line structure of urban distribution network in China gradually developing to the mixed form of overhead and cable,it is undoubtedly difficult for single-phase grounding fault section location and fault location.Therefore,it is necessary to explore the coordination between the new protection algorithm and the distribution automation mode to find the fault location timely and accurately,which is of great significance to quickly recover the fault and ensure the reliability of power supply.Firstly,choose the suitable for different power supply area provides the basis for fault handling mode,this thesis introduces the principle of distribution automation fault handling mode,a detailed analysis and comparison of the pattern characteristics,and a detailed analysis of grounding transient characteristics and characteristics of transient current mutation quantity and provide theoretical support for the following fault section location research.Secondly,in order to deal with the acquisition signal waveform time is not synchronized,upload the master station data transmission amount and part of the signal contains noise caused by the fault section location results are not good.In different power supply areas,the improved centralized monitoring mode and the distributed autonomous mode are adopted respectively,and the fault section location is realized by combining the respective algorithm flow.Firstly,in the background of distribution network with high demand for power supply reliability,fault location is carried out based on the improved centralized monitoring mode.Full-wave Fourier algorithm combined with similarity algorithm(Euclidean distance,cosine similarity)is used to preprocess the collected transient phase current information,and the processed data features are uploaded to the master station.The Local Outlier Factor(LOF)algorithm in the master station is used to analyze the fault location.Secondly,in the background of distribution network which requires high reliability of power supply,fault location is carried out based on distributed autonomous mode.Variational mode decomposition algorithm combined with Savitzky-Golay smoothing method was used to denoise the collected transient phase current mutation data,and the fault location was identified according to the fault identification method of direction parameters.The simulation results of the two schemes show that they can adapt well to the changes of line load,the connection of distributed power supply and the adjustment of the operation mode of neutral point.In the improvement of centralized monitoring model for fault section locating,can greatly alleviate the pressure of the upload the main data transmission,do not rely on denoising algorithm can deal with part of the acquisition signal contains noise,only data acquisition time synchronization problem,and through the experimental analysis in the synchronous error is within 1 ms delay does not affect the positioning accuracy of the programme of pattern;In the distributed autonomous mode,the problem of data time synchronization and large location communication volume is not considered,and the denoising algorithm can be used to deal with the situation that the acquisition signal contains noise.Finally,after the failure section is determined by the above two mode schemes.In order to determine the precise location of the fault quickly,the fault location is affected because the initial traveling wave head is not suitable for detection.The transient phase voltage data were collected based on the synchronous phasor measuring device of the distribution network.The LOF algorithm was used to analyze the alpha mode component of the voltage traveling wave after phase-mode transformation,and the time of the initial traveling wave at the fault point arriving at both ends of the fault was calculated.The precise location of the fault was obtained by combining the two-end traveling wave ranging formula of the distribution hybrid line.The simulation results show that this method can detect the initial wave head clearly in the multi-branch radial distribution hybrid line,and the error of ranging results is controlled within 20 m and the relative error is less than 1.0 %,and it is not affected by the fault type,transition resistance and initial phase Angle.From the above experimental results,it can be seen that in the simulation environment,the two modes proposed in this thesis can well solve the problem of poor fault location and the location algorithm can overcome the problem that the initial traveling wave head is not suitable for detection,which has a certain theoretical reference value.