Research On Analysis Of Lightning Fault Simulation And Classification Of Its Transient Characteristics On Transmission Line

It is demonstrated that lightning stroke is a significant cause for transmission line faults based on the statistical operating data of power system. We have obtained kinds of measures to decrease the damage of lightning, which includes erection of lightning shield line and the adjustment of its protection angel, line arrester, reducing the tower grounding resistance and optimization of line structure to increase the line insulation and so on. The damage induced by lightning has not been reduced to an ideal level by traditional lightning protection measures, it is essential to disconnect the fault part automatically when fault is generated by lightning while the protection device does not perform an operation when fault is not generated. Two different cases are generated when lightning strike on transmission lines and electrics devices:in the first case, fault is generated due to the high intensity of lightning wave, in which the protection should operate reliably, in the other case, fault is not generated with weak lightning wave, in which the protection should not operate. Due to the incorrect operation of wave protection, a discrimination method with high accuracy and real-time performance is in urgent need to distinguish the two cases.The basis of electro-magnetic transient simulation and lightning stroke is introduced to establish the basic model of different components to establish a whole transient simulation model in ATP-EMTP. The influence of impulse corona and coupling ground wire is emphatically considered simultaneously in this paper to analyze their influence to transient calculation in counterattack and detour lightning. The simulation model is established based of the research of the generating mechanism and equivalent circuits of impulse corona and coupling ground wire. It is suggested in the simulation result that the fault voltage after lightning stroke is influenced in a certain level after comprehensive consideration of the two factors. The difference of wave characteristic between counterattack and detour lightning is summarized to provide support for the discrimination of them.We get the waveform by changing the structure and parameters of power system in the following cases:lightning strikes on tower without fault generated, lightning strikes on tower with fault generated, lightning strikes on ground wire without fault generated and lightning strikes on conductors with fault generated. Flat structure element is chosen to process the simulation waveform to decrease the influence of glitch on identification results as the filtering effect of mathematical morphology.The transient characteristic in different cases is extracted after the wave is filtered by mathematical morphology by the method of linear fitting which consist the criterion for the distinction of the two cases to provide basis for operation of traveling wave protection. It is suggested that this idea improves the reliability of fault distinction by mass simulations.