Surge Analysis Of Lightning Tower Based On FDTD

The surge signal generated in the power facility is a key step in the lightning protection design of the power system.In the lightning surge analysis of power equipment,the use of electromagnetic transient analysis software has greatly improved the accuracy.However,the simulation of electromagnetic transient analysis software is based on a rough and simple model.The analysis of the spatial propagation process of lightning has yet to be studied.For example,the surge of the waves along the conductor propagates unevenly waiting to be solved.This derives the analysis of the surge along the transmission tower or the transmission line or the ground.Most of the lightning strikes in the domestic lightning protection design are analyzed by means of electromagnetic transient analysis software,analyzing the towers and strike back.Because the electromagnetic wave propagating along the lightning rod tower is non-transverse electromagnetic wave,there will be some error in the simulation result using EMTP software for larger and more powerful transmission towers.Using the finite difference method of time domain to simulate the lightning tower from the angle of electromagnetic field can simulate the transient process inside the tower accurately,and can more effectively estimate the lightning protection level of the transmission line and tower insulator.This paper first introduces the application background of finite difference method in the field of lightning field at home and abroad,and briefly describes the basic principle of time domain finite difference method and the equivalent processing method of fine wire based on quasi-static field derivation.Domain finite difference method,including the modeling of the lightning channel in the time domain finite difference method,the modeling of the transmission line and the lightning protection line,the modeling of the insulator and the approximation of the tower body model,and so on.The error of the equivalent model is less than 2%,and the finite difference method in time domain is used to simulate the surge of the lightning tower.The simulation of the single tower is carried out on the transmission line and lightning line.The current waveforms at both ends of the insulator are significantly increased and the short time reaches the peak after the insulator is broken,and the insulators of the upper phase and the middle phase are punctured at 322ns and 375ns respectively.The breakdown voltage is about 1400kV,while the lower phase of the insulator at 824ns only breakdown occurs,the breakdown voltage of about 1100kV.Without adding insulators,the on-line surge current and space electric field are obtained.At the same time,two double-pole towers with tower distance of 350m are simulated,and the waveform of the online current is analyzed.The current amplitude of the second tower is slightly higher than that of the first tower.In the ATP-EMTP,the multi-wave impedance model of the same tower is established and simulated.After the comparison between the online current waveform and the FDTD simulation results,it can be seen that the results of FDTD and ATP-EMTP program are close to each other,while the peak FDTD simulation results on the upper phase are 275A lower than the EMTP simulation results,and the results of FDTD simulation in the attenuation after waveform are always lower than that of ATP-EMTP simulation results about 900A,and the reason for this phenomenon is mainly due to the electromagnetic induction phenomenon of the lightning current flowing in the tower and the overhead line.The ATP-EMTP software simulation does not take into account the problem of electromagnetic wave propagation in space,so some energy dissipates into space,resulting in ATP-EMTP analysis results to be too large.