Research On Intelligent Line Selection Of Single-phase Ground Faults In Arc Suppression Coil Grounding System

As neutral point grouding via arc-suppression coil is widely used in small current grounding system, a lot of fault line selection methods based on steady-state component are no longer applicable. For this reason,some researchers proposed a fault line selection method based on transient component which is widely used. Although there are a lot of research on the loop grounding system of single-phase grounding fault line selection, the actual situation of a fault scene can be very random and which can result in great influence on the actual line selection, so the effect of field application of fault line selection is still not ideal until now. After an in-depth study on fault line selection technology, this article proposes a new method of fault line selection based on transient component.First of all, this article analyzed the transient characteristics of single phase fault in resonant grounding system,derived the transient capacitance current, transient inductance current and synthesis of transient fault current transient expression. Then, on this basis,a distribution network simulation model was built on the use of MATLAB/SIMULINK to simulated analyze the transient characteristics and summarize the rule of transient characteristics under different fault situation, so as to provide theoretical basis for the following study.Secondly, this article used Modified Ensemble Empirical Mode Decomposition(MEEMD) to decompose the zero sequence current, and then get Intrinsic Mode Function(IMF) arranged in order from high to low. This method not only can effectively suppress white noise in Empirical Mode Decomposition (EMD), but also greatly reduces the pseudo-component, inhibits the modal split and generates better orthogonality of decomposition compared with Ensemble Empirical Mode Decomposition (EEMD) and Complementary Ensemble Empirical Mode Decomposition (CEEMD). On the basis of this, the corresponding frequency band energy of each IMF was calculated, and the correlation coefficient is obtained through the correlation analysis of the IMF component with the original zero sequence current, and then the correlation coefficient is given as the weight coefficient to the frequency band energy. Furthermore, the weighted frequency band energy was accumulated and the energy of each line is obtained. Thus, the proportion of energy is obtained by normalizing and will finally form a line selection criterion.In the end, according to the actual distribution network in China, a distribution network simulation model with hybrid transmission lines is set up, and the parameters such as fault distance, fault closing angle, transition resistance and so on can be selected correctly.Then,next part selected the Anfeng substation as the simulation object and set up and the simulation model combined with the actual situation. The simulation results show that the proposed fault line selection method could choose the fault line correctly under the above fault conditions, so the method has certain feasibility and application value.