Analysis And Protection Against The Over Voltage In The Electric Railway Reactive Compensation Equipment

The power supply object of the electric railway traction substation is the electrical locomotive. Because the electrical locomotive is single phase burden, it can cause larger negative sequence harmonic wave, thus results in the power factor of the traction power supply net work decreasing and brings influence to the electric power system. There are many varieties of approaches to increase the power factor of the traction substation; the generally adopted one in our country is installing fixed shunt compacitor compensation in the low pressure side of the traction substation and it is generally opened and closed by the vacuum breaker. Because the vacuum breaker's ability of arc extinction and blow-out in high frequency is very good, many accidents of burning down the capacitor and reactance have taken place in the traction substation while using the vacuum breaker to close and open the shunt compacitor compensation. It seriously affects the electric railway's safe oprations, thus it urgently needs to study the over voltage produced in the transisent course of opening and closing electric railway shunt compacitor compensation.In the paper, it first introduces the present conditions of the electric railway idle work capacity factor, the principle, function, schema and main diagrams of the shunt compacitor compensation and the application and present status of the national reactive compensation pattern as well. Then it analyzes theoretically and computes the transitional course of closing and opening the electric railway shunt reactive-load compensation equipment. It gains the mathematical formula of the voltage and current of the capacitor and reactance in the transitional course of closing and opening the shunt compensator. According to the real parameter of the traction substation shunt compensator, the paper also does engineering compute of the voltage and current of the capacitor and reactance in the closing and opening transitional course and analyzes the copute result.Secondarily, the paper simply introduces the function of the ATP software and explains the building means of the simulation model for the transisent course of closing and opening the shunt compensator in the ATP. It uses the ATP to do electromagnetic transisent simulation of the voltage and current of the capacitor and reactance in the transisentional course of closing and opening the shunt compensator in the paper and gains the transisent simulation waveforms and analyzes them, thus tests and verifies the theoretical analysis and compute in Chapter three is right for the transitional course of closing and opening the electric railway shunt reactive compensator.Finally, the paper presents several measures of reducing the over voltage and current in the transisental course of closing and opening the shunt reactive compensator, including the breaker's choice, RC protective installation, MOA protective pattern and choosing phase control strategy for closing and opening. First, it simply introduces the theory of the four protective measures, especially uses the ATP to build model and simulate the protect effect of the RC protective installation and MOA protective pattern, finally reaches the conclusion that the two protective pattern both can protect the shunt compensator and the protective effect of the MOA is better than the RC protective installation.