Research On Relay Protection Scheme Of Full Parallel AT Power Supply Traction Network

Relay protection is a safety line of traction power supply system.Its purpose is to cut fault lines quickly,reliably and selectively.The protection of fully parallel AT power supply traction network is always a difficult problem because of its complicated structure.When a short circuit fault occurs in one of the lines of the full parallel AT traction power supply system,the existing protection scheme cannot identify the fault line,and all the two lines will be cut off,and then autoreclosure is used to restore the power supply of one of the lines.This not only enlarges the scope of blackouts,but also prolongs the time of restoration of power supply.Moreover,the circuit breaker of non-fault line will also undergo a tripping and reclosing process.The service life of non-fault circuit breakers will be reduced and the economic burden of traction power supply system will increase.Firstly,this paper analyzes the structure of the full parallel AT traction power supply system,the power supply mode from the traction network to the electric locomotive,the configuration of the relay protection scheme of the existing traction network and the time matching relationship.After analyzing the operation process of the existing protection scheme when transient and permanent faults occur in the full parallel AT traction power supply circuit,it is found that the existing protection scheme has the problems of selectivity and insufficient rapidity.Secondly,by calculating the distribution of conductor current when T-R,F-R and T-F short-circuit faults occur between substation and AT substation and between AT substation and section post,the scheme of directional current protection for power supply arm is deduced.According to the actual parameters of a power supply arm in a passenger dedicated line in China,the simulation model of relay protection for the full parallel AT traction power supply system was built with MATLAB/simulink software.The comparison between the simulated short-circuit fault data and the actual short-circuit fault data verifies the correctness of the model.At last,the model is used to simulate the short-circuit current amplitude and power direction when short-circuit fault of T-R,F-R,T-F occurs at every thousand meters,between substation and AT substation and between AT substation and section post.According to the simulation data,the protection can reliably distinguish the fault line,and can quickly remove the fault,and does not affect the normal operation of the non-fault line.The selectivity and rapidity of relay protection in full parallel AT power supply traction network are improved.