Lightning Strike Fault Type Of 500kV Transmission Line Based On Electromagnetic Signal Identification Method And Device Development

With the continuous expansion of power grid scale,the total mileage of ultra-high voltage transmission lines continues to increase.However,it is easy to be harassed by lightning during operation due to its high position,many erection cycles,long transmission distance and complex landform,which threaten the stability and reliability of the system and even cause serious economic losses.Therefore,it is of great significance to accurately locate lightning strike faults to realize rapid fault repair and identify lightning strike fault types,so as to develop more targeted lightning protection measures and improve lightning resistance level.The main contents of the paper are as follows:Aiming at the problem that the fault type of lightning strike line can not be identified accurately,an identification method based on improved Hilbert-Yellow transform is proposed.Firstly,a 500kV double-circuit simulation model of the same tower considering multiple factors was established in the ATP-EMTP platform to comprehensively analyze the transient process of the line after lightning failure.Secondly,the combined empirical mode decomposition(EEMD)and Hilbert transformation were carred out for the tower incoming signals.The intrinsic mode function(IMF)and its instantaneous amplitude were obtained respectively.Finally,the variance contribution rate of each IMF in the original fault signal was determined.The variance contribution rate of IMF1 in the original fault signal was more than 40%,and the other contribution rates were less than 25%.However,the variance contribution rate of the fourth-order IMF of the collision failure signal is not more than 40%,and is relatively balanced.On this basis,the stability of each IMF contribution rate is verified by changing the parameters of the model.The results show that the IMF contribution rate of the first four stages around the strike is basically not affected by the amplitude of lightning current and ground resistance,and has a stable and clear limit,which can be used as the basis for the classification of lightning fault types.In view of the existing monitoring device can not realize the lightning current data fast and accurate full wave sampling,this paper designs a lightning monitoring device and lightning background management system based on Roche coil.The device realizes the collection and preservation of lightning data and the location of lightning strike point through the acquisition module,coordinate positioning module and storage module,and adopts the transmission mode of chain network to realize the transmission of data.The background system realizes data receiving,processing and display through Chart and MapXtreme controls and Baidu Map API interface.The test platform is built in the laboratory.The results show that the terminal device can basically realize the full wave acquisition of fault signals,and the method can effectively identify the types of lightning faults,and verify the feasibility of the method,and provide a reference for taking targeted lightning protection measures,lightning warning and lightning risk avoidance.