| When the traction system is struck by lightning in the contact network of an overhead bridge section,overvoltage is generated on each body of the electric locomotive,leading to insulation breakdown of on-board equipment and affecting the safe operation of the electric locomotive.To improve the lightning protection level of electric locomotives,the influence of overvoltage on the locomotive body was analysed and protective measures were proposed by studying the propagation law and characteristics of lightning overvoltage on the body of the locomotive under different lightning conditions.The main contents of this thesis were as follows:(1)The simulation model of the overvoltage for electric locomotives in the viaduct section was established,and the simulation analysis of the overvoltage of the electric locomotive body when the lightning strikes the contact line T,the protection line PW,the forward feeder F,and the ground wire G was carried out.The results showed the impact on the overvoltage of the locomotives was greatest when lightning struck the contact line T of the traction network.(2)According to the amplitude and attenuation characteristics of the vehicle body lightning overvoltage,the influence of the installation position and type selection of arrester,the grounding method of electric locomotive and the height of overhead bridge on the vehicle body overvoltage was studied.The simulations were carried out for different lightning conditions,and the results showed that the largest overvoltage located in vehicle body No.2.The farther the vehicle body was from the pantograph,the overvoltage was smaller,and the waveform showed the form of attenuation oscillation.(3)For the problems of poor impact resistance and discharge characteristics of traditional Metaloxide Surge Arrester(MOA),the suppression measures of External Series Gap Arrester(ESGA)was proposed.The lightning resistance level and lightning trip rate of the two models was simulated and analyzed,and the results showed the lightning protection performance of ESGA was higher than that of MOA.(4)The strategy of connecting Surge Protection Device SPD in parallel with the grounding resistance was proposed to solve the problem of high overvoltage amplitude and significant oscillations in the direct grounding and parallel capacitores for electric locomotives.Comparing the three methods,the simulation results showed the amplitude of the overvoltage of each vehicle body can be reduced to less than 3k V by using the parallel SPD,and the amplitude of the damped oscillation was more moderate.(5)The strategy of increasing the height of the protective line PW for lightning protection was put forward to overcome the shortcoming that the higher the height of the viaduct leaded to the larger amplitude of the vehicle body overvoltage.Comparing the protection line PW with different heights,the simulation results showed the lightning overvoltage to below 3k V when a height of 9.5m. |
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