Analysis of Traction Reflux Characteristics of EMU and Improvement of Its Protective Grounding System

The traction reflux characteristics of an electric multiple unit (EMU) are directly related to its safe operation. It is of great engineering value to improve the reflux characteristics by improving the protective grounding system. The typical Chinese EMU with the eight-car power distribution marshaling and decentralized grounding model is taken as the research object of this study, and the circuit model of the traction reflux system is established by Multisim software, the effectiveness of which is verified by field tests. Combining the simulation and measured data, the distribution law of the traction current is analyzed. Based on the advantages of different grounding modes, three improvement schemes of the protective grounding system are proposed. The results show the following: 1) the circuit model of the traction reflux system is effective; 2) the traction current is mainly discharged from the end cars to the railway track; 3) the improvement schemes of the protective grounding system under the normal operation can also improve the traction reflux characteristics under the power loss condition; and 4) based on the proposed protective grounding improvement schemes, on the condition that the car body potential meets the standard requirements, the maximum grounding current amplitude is reduced to 48.4% of the original value, the circulating current is eliminated, the maximum current difference between the two axles of the same coach is reduced to 5.2% of the original value, and the effectiveness of the improvement schemes is verified by field tests.

I. Introduction

Railway transportation has developed rapidly in China due to the advantages of rapid speed, high capacity, and low pollution [1]–[3]. According to the characteristics of power layout, an electric multiple unit (EMU) can be divided into power-concentrated multiple units and power-distributed multiple units, wherein the power of multiple units is mainly concentrated in both end cars or it is distributed in each car, respectively. The typical marshaling mode of China’s EMU is the eight-car power-distributed marshaling [4].