Research On Filtering Algorithm For The Grounding Potential Difference Signal Caused By High-voltage Disconnector Operation

When the disconnector is operated in the high-voltage intelligent substation,the very fast transient overvoltage(VFTO)can result in the grounding grid potential difference.This interference signal is coupled to the transmission signal of the secondary cable,which can cause the inaccuracy of the measurement and the misoperation of the equipment.In order to improve the anti-interference ability of relay protection,the disconnector operation model is built,and the signal characteristics of the primary side are analyzed.To figure out the mechanism of the interference signal,the coupling path of the grounding grid potential difference is analyzed.According to the characteristics of the interference signal,a filtering algorithm for the interference signal caused by grounding grid potential difference is proposed.By measuring actual signals and building simulation platform,the verification experimental is carried out.The main contents of this paper are as follows:(1)Analysis of the disconnector operation overvoltage: The principle of arc reburning and extinguishing during the disconnector operation is studied,and the signal characteristics of the primary side are analyzed.To simulate the transient process of disconnector operation,the disconnector operation model is built.Meanwhile,the time domain and frequency domain characteristics of the VFTO signal are summarized.(2)Coupling path of the grounding grid potential difference interference signal: Based on the layout of the intelligent substation,the coupling path of the "grounding grid ~ two cable ~ intelligent component" is analyzed.The model of the grounding grid in the substation is established to study the mechanism and characteristics of the grounding grid potential difference.A multi-conductor transmission line model is established and solved,the coupling interference signal in the intelligent equipment is calculated.(3)Algorithm solving the grounding grid potential difference interference signal: According to the characteristics of the ideal sampling signal in the power system,the constraint condition of sampling values is analyzed.An algorithm to deal with the interference signal caused by the grounding grid potential difference is proposed,with the starting element and the decision element judging the signal state quickly.Due to the high amplitude,short rise time and wide bandwidth of the interference signal caused by the disconnector operation,the wavelet transform is used as the filtering algorithm through the signal decomposition and reconstruction.The simulation results show that the algorithm can retain the low-frequency signal and eliminate the high-frequency signal with the appropriate wavelet threshold,reducing the root mean square error(RMSE)and improving the signal-to-noise ratio(SNR).The problem of the traditional filtering algorithm when processing high frequency signal is solved and both of the rapidity and the stability can be meet.(4)Experimental verification: The disturbance voltage on the local intelligent control cubicle caused by the disconnector operation is measured in the intelligent substation,and the characteristics of the interference signal are analyzed and summarized.According to the actual workring condition,the simulation platform based on FPGA and DSP is built to carry out the related experiments,and the experimental results verify the effectiveness of the filtering algorithm.