The Research Of The UHV Converter Stations Secondary System On Lightning Protection

Lightning protection at the converter station is a necessary task to avoid secondary equipment from being damaged by natural disasters.The general lightning protection measures are to install lightning rods or lightning protection lines to introduce lightning current into the ground.However,after the lightning current flows into the grounding grid,the ground potential is raised,and the ground potential is counter-attacked,causing damage to the secondary equipment.Because of the damage caused by lightning strikes,the DC blocking accidents have occurred at home and abroad.For this reason,it is imperative to strengthen the lightning protection work of secondary equipment.In the paper,the lightning striker discharge tube and the structure characteristics of the varistor,the lightning protection principle of the discharge tube and the advantages and disadvantages of the lightning protection are briefly discussed.The lightning protection function and working state of the low voltage arm of the DC voltage divider are discussed.The characteristic sets the corresponding transfer function and analyzes its transient response characteristics.Secondly,the lightning protection simulation module of discharge tube and varistor based on EMTP software platform is established,and then the overall simulation model of voltage divider secondary loop is derived.From the DC voltage divider,the low-voltage arm lightning protection device discharge tube can recover the normal voltage after experiencing a transient process of about 100 milliseconds after the lightning strike.This conclusion is consistent with the previous theoretical derivation.However,once the system voltage recovery time exceeds the set value of the DC undervoltage protection,the DC undervoltage protection will malfunction.In this paper,the power supply side lightning protection of the DC voltage divider is improved.The varistor is connected in series with the discharge tube and then connected to the secondary system of the converter station.It is found that after the operation,the transient process is shortened and In the case of meeting the DC undervoltage protection setting value,the DC undervoltage protection malfunction is avoided,and the damage of the secondary system equipment is reduced.Finally,the paper combines working examples to build a working experiment circuit in the electromagnetic compatibility laboratory of the working unit.After adjusting and improving,the best lightning protection mode of the converter station is obtained.In this experiment,the voltage recovery time was measured by connecting different types of discharge tubes and varistor in series,and the test results of the residual voltage values of the system were greatly different.After comparative analysis,the transient process is selected to be the shortest,and the voltage is restored to the same group combination mode as the normal value of the low-voltage bridge arm.Through the engineering example of the converter station,the construction workers are assisted to complete two sets of converter stations.The lightning protection device of the system is installed.