| Railway is an important infrastructure,which plays a key role in China's comprehensive transportation system.The railway signal system ensures the safe operation of trains on the railway.High speed,heavy load and electrification are the development trend of modern railway.In order to ensure transportation safety and work efficiency,train control system need about microelectronics,computer and communication technology as the core is constructed,which makes railway signal equipment more sensitive to lightning.The lightning protection of railway signal equipment has been studied and practiced for a long time,but the train accidents caused by lightning are still frequent in recent years.The installation of Surge Protection Device(SPD)is an important lightning protection method for railway signal system,but there are still some deficiencies in the dynamic process analysis of device model and on-site configuration.This thesis focuses on two kinds of surge protective devices,Gas Discharge Tube(GDT)and Metal Oxide Varistor(MOV),commonly used in railway signal system.Through the established simulation model,the dynamic response process of the combination of surge protective devices is analyzed,and the optimization suggestions are put forward.The main research works are as follows:(1)The current and energy characteristics of lightning current are analyzed by using three functional models of double exponential function model,Heidler function model and pulse function model.On this basis,according to the requirements specified in GB/T 17626.5-2019 electromagnetic compatibility test and measurement technology surge(impact)immunity test,the models of 1.2/50-8/20 ?s combined wave generator and 10/700-5/320 ?s combined wave generator are built and their waveforms are analyzed and verified;the actual surge generator is made,and the generated waveforms are tested and verified to meet the requirements.(2)The simulation model of SPD,especially GDT,is completed.The dynamic process of response of GDT and MOV is analyzed,and the model of combined wave generator is used for testing and analyzing.By designing and implementing of the lightning protection test board,the surge impact test is realized,and the rationality of the simulation model is further verified.(3)Dynamic analysis is carried out by using the model of combined wave generator and surge protector.This thesis analyzes the protection effect of the combined circuit for the surge signal and the dynamic response process of the surge protector in the combined circuit,According to the simulation results,the series protection has no enough improvement in protection effect,and the effect is better when parallel protection is done;the solution of inductance as decoupling element of parallel protection can better protect the MOV and avoid its deterioration.the analysis and simulation of the use of SPD in the railway field are carried out,and the optimization suggestions for the use of SPD are put forward in outdoor application,it is better to select SPD with the conduction voltage far greater than the system working voltage,while for indoor situation,it is just a little greater than the system working voltage;it is recommended to give priority to the use of parallel protection;the "third track" effect actually has a very low probability,so SPD can be used for longitudinal protection. |
PDF Full Text Request