Research On The Method Of Small Current Grounding Fault Line Selection Based On Multi-source Information Fusion

With the continuous enhancement of my country’s comprehensive national strength and rapid economic development,the era of rapid development requires a stable and reliable power system for support,so the staff must ensure the stable and reliable operation of the power system.The grounding method of my country’s 3k V～66k V distribution network basically uses low current grounding.When this type of fault occurs,its characteristics are short transient time,weak fault signal characteristics and difficult to extract,which makes line selection more difficult..In recent years,although many line selection methods have been proposed,any single line selection method is difficult to adapt to the complexity of the power distribution system,so it is necessary to study efficient and feasible methods.First,the transient characteristics and steady-state characteristics of single-phase grounding faults in low-current grounding systems under three different grounding methods are analyzed,and the ground capacitance distribution diagrams when single-phase faults occur under three different grounding methods are given.The calculation methods of zero-sequence voltage and current are respectively given,and the characteristics of zero-sequence current under different neutral grounding methods are summarized,including transient capacitive current,transient inductance current,and transient grounding current during the fault period.Secondly,a low-current ground fault model based on MATLAB was built,and the three factors that have the greatest impact on the steady-state and transient characteristics,namely the location of the fault point,the initial angle of the fault,and the fault grounding resistance,were changed.In the case of the fault,it is found that the fault feature is the least obvious when the fault point is far away from the bus(25km),the initial fault angle is 0°,and the fault grounding resistance is large(2000Ω).Then,use the traditional transient steady-state quantity line selection method,zero-sequence current fundamental wave,zero-sequence current fifth harmonic ratio amplitude ratio phase method,active power method for arc suppression coil grounding,and reactive power method;for steady-state quantities Line selection is judged based on the characteristics of the fifth harmonic of the faulty line and the largest active power amplitude and the direction opposite to the other non-faulty lines.For line selection by transient quantity,two methods are selected: transient zero-sequence current comparison method and IMF1 energy ratio based on VMD algorithm.The line selection criterion and process are given.At the same time,MATLAB/SIMULINK is used to build The simulation model is verified,and it can be obtained that the above is highly accurate regardless of whether it is based on the steady-state quantity or the transient state.However,when the conditions of the ground fault occurrence(fault initial angle,fault distance,fault ground resistance)are changed,There will be misjudgments.Finally,in order to better solve the above problems,based on the D-S evidence theory,fault information fusion is carried out to realize the fusion of four single criteria and make full use of the line selection characteristics of each single criterion.Evidence combination based on DS evidence theory,first select the fusion feature quantity,construct the fault measurement function,calculate the function trust value of each line under each method,use the distributed fusion algorithm and combine the evidence synthesis rules to combine the evidence to get the final Combine the evidence based on the reliability function value to get the result.Changing different fault conditions and multiple simulation tests can verify the feasibility of the fusion criterion in fault line selection.