A Uniform Model for Stray Current of Long-Line DC Metro Systems

With the rapid development of the metro, a series of problems caused by the stray current is becoming increasingly serious. Evaluation of stray current is the primary but difficult step for dealing with the problems. In fact, since metros are usually constructed by cut-an-cover tunnel, shield tunnel, and viaduct, the metro structure is one of the most important factors of stray current. It is significant to evaluate stray current in the long line with the variable metro structures. Based on this, a uniform model is built in this article. The return current system is equivalent to multiple differential units considering the variability of the metro structure, and differential units at each location can be set according to the actual metro structure. Furthermore, uniform equations for solving stray currents are deuced based on the electrical relationships of differential units. For variable metro structures, uniform boundary conditions are discussed to solve the equations. The model is verified by comparing the test data and simulation data of Shenzhen Metro. Finally, stray current along the long line is evaluated in this article. It is shown that the stray current is smaller along the long line, which is formed by the viaduct.