Research On Fault Location Method Based On Comprehensive Criterion And Fault Line Selection Method Based On S-Transformation For Distribution Network

In the power system,the safe and stable operation of the distribution network is directly related to the user’s power supply reliability,and single-phase grounding is the most common fault in the distribution network.In this paper,we study the line selection and positioning of single-phase ground faults under the most widely used grounding methods:neutral grounding and arc-suppression coil grounding.Firstly,the paper classifies the current situation of single-phase ground fault line selection and positioning from multiple angles,expounds its characteristics for each type of discriminant method,and points out the problems that should be paid attention to in the application.After that,the electrical quantity on the line after the fault occurred,especially the distribution of zero-sequence voltage and current,is analyzed.The paper analyzes the simulation module of single-phase ground fault analysis of distribution network.Because the existing simulation software build model is relatively fixed,and it can not meet the requirements of dynamic adjustment of parameters and topology,the paper develops the system simulation software twice.Through the combination of SIMULINK and GUI,a new type of distribution network fault analysis simulation platform is built.The model is built at one time,and switches are controlled from the outside through a graphical user interface.The paper proposes an effective treatment method for the extraction and analysis of signal feature in the line selection process.The S-transformation time-frequency processing technique is introduced,and its operation process and properties are analyzed.The advantages of S-transform in extracting signal feature are showed when compared with fast Fourier transform and wavelet transform.The S-transformation is used to extract the amplitude and phase angle information of each sampling point of the first half of the fault zero-sequence current in the characteristic frequency band.The similarity of the signal is quantified by the method of energy relative entropy to form a complete line selection method.The simulation verification shows that the method effectively reflects the fault condition.In order to avoid the shortcomings of using a single fault location criterion,the paper proposes a positioning method that comprehensively utilizes multiple criteria,and three measures are proposed to construct a evaluation system of single-phase grounding fault location.The fault direction measures are used to compare the significant level of the same feature component in different sections;the reliability indexes are used to judge the degree of coincidence of the fault component of each section with the fault law.The direction measures and the reliability indexes are used to quantify the probability that one section is the faulty section each single fault location under each criterion.The criterion measure indexes are proposed as the basis for measuring the validity of the criterion,and finally the judgment result of multiple criteria is integrated according to the validity of the criterion.The simulation results show that the proposed method is resistant to complex conditions such as small initial angle of voltage and transition resistance at fault point.