Research On Protection Principle Against Wrong-Phase Short Circuit Of The Ac Traction Supply System

In case of the electric locomotive passing through the electrical system phase-splitter by means of putting on pantograph, wrong-phase short circuit of the AC traction supply maybe take place. For the arc resistance is nonlinear and high, the conventional feeder protections, such as impedance protection and current protection, maybe fail to trip off. The arc is a kind of high-power discharge phenomenon, which can be self-keeping. It doesn't need very high voltage to keep a long arc's steady burning, but it would make intense physical change and chemical reaction happen to the solid, liquid and gas around it. So wrong-phase short circuit happening at the exit of the AC traction supply system is dangerous. The protection for feeder has not been perfect yet. It is necessary that a special protection against wrong-phase short circuit is configured at the exit of the AC traction substation.In this thesis, the cause of wrong-phase short circuit arc is analyzed; a mathematical model of high impedance arc in traction supply system is established and discussed in detail and a digital simulation model of arc is built with the simulation software SIMULINK based on MATLAB. The validity of the model is proved by comparison with the results from the power system field records arc voltage and current measurements and from the lab. A protective principle used in wrong-phase short circuit is presented in this paper by analyzing the fault character of voltage and current.A digital simulation model of electric locomotive is built with the simulation software SIMULINK based on MATLAB. Counter-electromotive force of DC motor is simulated accurately with the model. Conduction angle a is calculated by use of the relationship between the function of locomotive tractive characteristic and rectifier circuit. So AC side datum of electric locomotive are gained. The magnitudes of harmonics have been gotten in several different work conditions. At last, the accuracy, efficiency and feasibility are indicated by analyzing the simulation datum of the arc wrong-phase short circuit and the running of the electric locomotive.