Transmission Line Fault Transient Protection Method Combining EMD-WVD And Cuckoo Algorithm

In recent years,ultra-high-speed protection methods based on transient components have developed vigorously.Among them,the unique transient protection principle of waveforms has become a research hotspot due to its comprehensive time-domain and frequency-domain feature information and its small impact on fault conditions.However,when using the unique principle of waveforms to synthesize time-frequency characteristic information for transmission line fault protection,the fault waveforms must be matched with the sample library waveforms one by one.The calculation is cumbersome and takes a long time,which greatly affects the rapidity of protection.In order to promote the practicality of the transient protection principle based on waveform uniqueness,the paper proposes a combination of empirical mode decomposition(EMD)-Wigner ville disturbution(WVD)and cuckoo algorithm Transient protection method for transmission lines.The paper first introduces the generation mechanism of the transient signal in detail;analyzes the transmission of the transient signal on the transmission line:establishes the frequency-dependent change model of the transient waveform,and analyzes the phase-mode transformation of the transmission line;The transmission characteristics are analyzed:the reverberation process of the transient signal is studied,the influence of the wave stopper and busbar structure on the transient signal is studied in depth,and the frequency characteristics of the reverberation coefficient of the line boundary are analyzed;The characteristic analysis of the transient signal indicates that when the fault occurs,the difference of the waveform characteristics of the transient signal on the same line and the adjacent line leads to the unique protection principle of the waveform.Then,based on the principle of waveform unique protection,a method for transmission line fault transient protection combining EMD-WVD and cuckoo algorithm is proposed:this method uses EMD to decompose the fault transient signal to obtain single-component signals in different frequency bands;Each single-component signal is similar to the original transient signal,and the true transient signal components are selected;then the true components are separately calculated for WVD,and the WVD of all true components are linearly superimposed to obtain the energy spectrum density map;using cuckoo The algorithm continuously and iteratively matches the energy spectrum density map of the fault transient signal and the energy spectrum density map in the fault sample library to calculate the similarity.According to the similarity,the internal and external faults are discriminated to realize fast and reliable protection of transmission line faults.Finally,the method proposed in the paper is simulated and verified:the time-frequency analysis of the transient signal of EMD-WVD is verified;the similarity and difference of the energy spectrum density diagram of the refill of the transient signal in and outside the region;the cuckoo algorithm is analyzed The rapidity of the simulation;simulation of different fault locations,different initial phase angles and different transition resistances,different fault types,different intensity Gaussian white noise,different sampling frequencies and different time windows.Simulation results show that the method uses the panoramic fault information of the transient signal in the time-frequency domain to effectively overcome the defects caused by the use of local fault feature information in the time or frequency domain of the transient signal.To improve the accuracy of fault transient waveform analysis,the cuckoo search algorithm can effectively improve the waveform matching speed,and it can quickly and reliably operate under various fault conditions,which is expected to promote the practicality of transient protection.