Research Of Transient Fault Line Selection In Resonance Grounding Distribution Network Based On The Hilbert-Huang Tranform

In recent years,with the rapid development of urban distribution network,the proportion of cable line is rising,capacitive current of single-phase earth fault increases,so the arc suppression coil grounding operation mode is widely used in the distribution network.Due to the compensation effect of the arc suppression coil,the method based on steady signal failed in single-phase earth fault line selection.Therefore,this paper studies the transient characteristics of single-phase grounding fault,and search for line selection scheme based on transient signals.This article combine phase mode transformation with fault component principle and dynamic circuit theory,and receive the failure modes network diagram and the dynamic equivalent circuit which is used to analyze the single-phase earth fault transient characteristics.With the dynamic differential equation to study the fault oscillation mechanism and the single-phase earth fault transient characteristics regulation,laying a theoretical foundation for a better principle of fault line selection based on transient component was proposed.On the basis of deep analysis of the single-phase earth fault transient characteristics,according to the differences of transient zero mode current of fault line and non-fault line in amplitude ? frequency distribution and mutation polarity,put forward two kinds of transient fault line selection scheme based on Hilbert huang transform.Use energy to measures amplitude and frequency distribution of transient zero mode current,combine empirical mode decomposition with energy method,define intrinsic mode energy and energy weight coefficient,compare the size of the energy weight coefficient of each line,forming line selection criterion,structure transient line selection scheme based on intrinsic mode energy.Considering that the ransient zero mode current mutation polarity of fault line and non-fault line is reverse,apply HHT singularity detection principle,compare the first order difference polarity of the highest frequency IMF component of transient zero model current of each line,forming line selection criterion,structure transient line selection scheme based on mutation polarity.Using MATLAB to establish two kinds of resonant grounding system model(overhead lines,hybrid transmission lines),simulations for the two proposed line selection schemes are performed under different fault conditions,the results verify the validity of the methods,analysis shows that the two proposed transient line selection schemes have high sensitivity and reliability,and the principle is simple,easy to implement.