Study On The Identification Of Lightning Over-voltage Of Transmission Line

Lightning over-voltage of transmission line is the main cause of line fault.Over-voltage caused by lightning stroke accounts for over 40% of total failure of transmission line.The damage caused by lightning over-voltage is even more serious in the areas of multi thunderstorm weather,complex terrain and high soil conductivity than other areas.If a lightning fault occurs,the power supply is interrupted.If handled improperly,the lightning wave will cause more serious consequences to the adjacent substation along the line.Therefore,how to reduce the lightning strike transmission line fault has become an important issue in the power system.In order to reduce the transmission line lightning fault,we need to identify the species of lightning over-voltage.Firstly,the theory of lightning over-voltage is studied.The process of the lightning are analyzed,and the main parameters of transmission line lightning discharge process were studied.According to the theory of lightning over-voltage,the classification and equivalent models of lightning over-voltage on transmission lines are analyzed.The lightning current path of the initial stage of the lightning strike over-voltage and the surge over-voltage is studied.And the three parts lay a model foundation for lightning strike simulation of transmission lines.Secondly,the transmission line is analyzed and modeled.Signals of back flashover and shielding failure is analyzed.The simulations of lightning current,towers,insulators and lines have been carried based on the theoretical analysis,each part of the simulation model is determined through analyses,and the parameters of models are set through calculation.The lightning strike transmission line simulation model is composed of various models which have been debugged.On the basis of the model,the simulation of the over-voltage and shielding failure is carried out.Two types of lightning waveform are analyzed,which makes a groundwork for characteristic extraction.Finally,a lightning over-voltage identification system is developed in MATLAB GUI.The characteristics of different wavelet are analyzed.The suitable wavelet for lightning identification is selected by calculating.The zero mode component extraction,wavelet decomposition algorithm,and modulus maximum extraction of data are carried out.The modulus maximum ratio is designed to distinguish different kinds of lightning over-voltage.The transmission line lightning over-voltage identification system is developed,which can automatically identify the transmission line lightning over-voltage.