Research On Line Selection And Location Of Single-phase Ground Fault In Distribution Network Based On VMD And GST

In our country,the low-current grounding method is widely used in the neutral points of middle and low voltage distribution network.Under this method,the system can still continue to operate for a period of time after the occurrence of single-phase grounding fault.However,in order to prevent the fault range from expanding or developing into interphase fault,the fault location should be located and dealt with in time.However,for the fault location of small current grounding system,due to the harsh and changeable fault conditions,it is difficult to extract fault signal features,and the problem of fault location of distribution network has not been completely solved,especially with the widespread access of distributed generation,the problem of fault location of distribution network has become more complex.Based on this,the selection and section location of single-phase ground fault of active distribution network with branch lines are studied in this paper.Firstly,the fault characteristics of single-phase grounding fault of small current grounding system are analyzed,and the transient zero-sequence current with abundant fault information is taken as the fault characteristic quantity of fault line selection and section positioning.Then the factors affecting the fault characteristics of transient zero sequence current are analyzed.Considering the change of distribution network structure,the influence of branch lines and distributed power supply access system on fault characteristics is analyzed.The single-phase grounding fault model of small current grounding system is established and its related theories are simulated and verified.Secondly,because the fault characteristics of the transient zero sequence current change with the change of fault conditions,the effect of fault line selection based on its fixed characteristics is poor.This paper from the composition and distribution of transient zero sequence current characteristics from the hair,the paper analyzes the factors which lead to the change of the characteristics of internal and its change law of variational mode decomposition algorithm is introduced to extract characteristics of transient zero sequence current,the mutual correlation coefficient to calculate the modal component line features,according to the characteristics of the modal component label for the first time the only difference to judge the fault lines,if each line the same label,the further comparison feature modal component of energy and the initial polarity realization of fault line selection.For fault section location,because the existence of branch lines breaks the uniqueness of fault section features and increases the possibility of misjudgment,this paper divides the lines into regions according to whether the section contains branch nodes or not,and forms the corresponding section location principle according to the performance of each fault feature.At the same time,aiming at the problem that fault information is not fully utilized and the single criterion is located in a blind area,this paper proposes to construct multiple criteria based on generalized S transformation.Simulation results show that the proposed fault line selection and fault section location method can achieve the expected results under different fault conditions and has good adaptability and accuracy compared with other methods.Finally,combined with the field practice of a lOkV line,the effect of the above step-by-step positioning is investigated on the whole.The results show that the fault positioning research of"line selection before section determination" in this paper has better positioning effect,strong practicability and certain engineering application value.