Study On Harm Mechanism And Suppression Strategy Of Rail Voltage In Metro Power Supply System

In recent years,with the rapid development of urban rail transit in China,the occurrence of Metro operation accidents has also attracted great attention.Rail voltage of Metro DC traction power supply system is the potential difference between running rail and the earth.In the actual operation of metro,rail voltage may rise,which will cause harm to human body and equipment of Metro DC traction power supply system.Therefore,it is of great significance to study the harmful mechanism and restraining strategy of rail voltage over-voltage for ensuring the normal operation and personal safety of Metro DC traction power supply system.At present,the main measure to restrain the over-voltage of metro rail is to install the rail potential limiting device in the DC traction power supply system of metro.There are some shortcomings in the actual field application.In view of these shortcomings,this paper presents the optimization scheme and carries out simulation verification.Firstly,this paper analyses the principle and hazard of rail voltage in metro,and calculates the distribution model of rail voltage in Metro DC traction power supply system.It is concluded that the magnitude of rail voltage is related to rail longitudinal resistance,traction current,length of single power supply interval,rail-to-ground transition resistance and the location of Metro vehicles,and the rail voltage of Metro DC traction power supply system is established.Distribution model,using software MATLAB simulation analysis of the normal and abnormal state of the Metro line on the impact of rail voltage,verify the correctness of the theoretical analysis.Secondly,the commonly used rail voltage suppression measures are given:installing the rail potential limiting device;controlling the output voltage of the traction substation,and analyzing the state of the system grounding diode;installing the ultra-capacitor on the platform of the Metro DC traction power supply system,and verifying its effect by simulation.At the same time,the problems existing in the field test of rail potential limiter are also found.It is pointed out that the frequent movement of OVPD in Metro may be due to the improper cooperation between OVPD and platform shield door,and the OVPD blockade caused by the peak voltage of OVPD.According to the problems existing in the Metro OVPD site,the optimization scheme is put forward:the linkage optimization between the Metro OVPD and the platform shield door,that is,when the platform shield door is opened and the rail voltage is over-voltage,the OVPD action;the optimization of the Metro OVPD opening conditions to prevent the misoperation of the peak voltage on the OVPD from causing the OVPD blockade,that is,when the monitoring current of OVPD is greater than the stray current,the OVPD action coordination optimization of the Metro line OVPD action;That is to say,OVPD in each power supply area can monitor the whole line rail voltage,and OVPD action at the position of maximum rail voltage.Through theoretical calculation and simulation analysis,it is concluded that the three optimization schemes reduce the number of OVPD actions,stray current leakage and rail voltage.Finally,three optimization schemes of OVPD control are put forward,which provides a theoretical basis for rail voltage suppression strategy and OVPD control optimization of DC traction power supply system in Metro.