Research On Five-conductor Equivalent Model And Protection Setting Value Optimization For AT Traction Electrical Network

After entering the age of high speed and heavy load,the working performance of the traction power supply system and its relay protection has become the major factor restricting the transportation capacity and economic benefit of electrified railway.Limited by the recognition level and structure condition,the AT traction network,as the only transmission network of the AT traction power supply system,is not only prone to various short-circuit faults when light load,but also difficult to set the main feeder protection when heavy load.In order to fully grasp the short-circuit impedance characteristics of the AT traction network and improve the existing feeder protection algorithm,based on the AT traction network topolog,this paper accurately constructs the equivalent circuit model of the short-circuit between the wires of the traction network,and gives the optimized feeder protection setting-value through engineering calculation.Firstly,the power supply mode,characteristics and status of the traction power supply system and the feeder protection are analyzed,especially the all-parallel AT traction network.Secondly,based on the calculation of the conductor impedance for the traction network,the calculation method of the parameters for the all-parallel AT traction network is studied.At the same time,the five-conductor equivalent circuit of the all-parallel AT traction network is derived based on the field connection mode of the all-parallel AT traction network.The short-circuit impedance calculation is performed for single-line,double-line and all-parallel operation mode.Thirdly,by comparing the short-circuit impedance of common short-circuit conditions in different operation modes,the maximum short-circuit impedance of the system is obtained.Based on this,the main protection of the feeder protection is optimized,and the setting method and action criterion of the feeder protection are given.Finally,based on the RTplus real-time digital simulation system,the all-parallel AT traction network simulation model is established,and the semi-physical simulation system is built with some hardware.On this basis,the short-circuit conditions in differentoperating modes are simulated to verify the correctness of using five-conductor equivalent circuit to calculate the short-circuit impedance and the accuracy of the setting-value optimization for the feeder protection.The verification of the semi-physical simulation system shows that the five-conductor equivalent circuit of the all-parallel AT traction network can be used to calculate the short-circuit impedance and obtain the maximum short-circuit impedance,based on which the setting-value of the feeder protection can be optimized.Thus,the reliability of the feeder protection can be improved to meet engineering needs.