Research On Stray Current Protection In Dc Traction Power System Of Urban Mass Transit

With the rapid development of urban mass transit system, more and more attentions are paid to the problem of metal structure corrosion from stray current of DC traction power supply system. Stray current protection method can be developed by carrying out theoretical analysis and digital simulation of stray current. Suitable criteria for stray current protection designing, construction and operation that can insure long-term safety and reliability can also be found by theoretical analysis and digital simulation.In this paper a further discussion of the causes of stray current in DC traction power supply system and the corrosion mechanism of stray current to steel structure and metal pipeline is presented. Based on the digital simulation of DC traction power supply system, the properties and distribution of stray current are discussed in detail. By analyzing the influence of various parameters on stray current, methods to control stray current are proposed. The method proposed has applied in the stray current protection designing in Dalian rapid railway line 3. Chapter one is a brief introduction to the importance and present situation of stray current protection in urban mass transit system. The stray current corrosion mechanism to metal structure is introduced and mathematical model of typical DC traction power supply system is constructed in chapter two, on the basis of theoretical analysis and digital simulation analysis, the characteristics and distribution of stray current are obtained in one-way feeding and two-way feeding power supply system. The impacts of parameters, including length of feeding section, resistance per unit length of running rails, resistance per unit length of running rails/earth, traction load, resistance per unit length of the metallic-conductive interconnected structure and existence of drainage, on stray current are analyzed in detail in chapter three, effective methods of stray current protection in engineering designing are given. In chapter four, simulation analysis, implementation and the evaluation of Dalian rapid railway line 3 are introduced. It is found that the simulation analysis of stray current canprovide a proper design than others, so it holds far more distinctive economic and social benefits.