Study On Ground Reflux Of Traction Substation Under AT Power Supply Mode Of High Speed Railway

Nowadays,there are two main power supply modes for electrified railway,one is direct power supply,the other is AT power supply.Compared with direct power supply,AT power supply is better than direct power supply in terms of power supply voltage level,electromagnetic compatibility and reducing project investment,so it is more suitable for high-speed railway.However,because of the increasing traction load and the increasing train load rate on the line,the current of the whole traction reflux system will be correspondingly increased.As a part of the return current system,if the current flowing through the earth to the substation is too large,it will bring great hidden dangers to the safety of the equipment and personnel in the substation.Moreover,the system structure of AT power supply mode itself is more complex.Therefore,the detailed analysis of the ground return current of traction substation under AT power supply mode is of great significance to the design of future railway power supply system and safe and stable operation.In order to study the ground return current of traction substation,firstly,by analyzing the short circuit of traction power supply system under AT power supply mode,the corresponding simplified calculation model is established,the causes of the earth current in the system are analyzed theoretically,and the mathematical formulas of rail current and rail potential in the short circuit of AT power supply are obtained.Then the calculation formula of ground return current in traction substation is deduced.On this basis,the structure of complex AT power supply system and the current flow path in the line are analyzed.Through the principle of underground constant current field,the leakage current of rail and the potential generated by the leakage current of integrated ground wire near the ground grid of traction substation are solved,and the mathematical formula of the return current of ground through the ground grid is deduced.In this paper,a traction power supply system model is built on CDEGS platform,and validates the model by using the derived mathematical formula.By changing the parameters of the model,the soil resistivity,traction load,the number of grounding conductors in the grounding grid and the area of the grounding grid of the substation are analyzed.The effects of these parameters on the current distribution of the whole reflux system,especially on the ground reflux of the traction substation,are analyzed.Then the field test is carried out in Yangxian West Substation,the problems in the measured results are analyzed,and the reasons for the problems are explained according to the results of simulation analysis.On this basis,a feasible solution is put forward based on literature research and engineering practice.