Investigations On Controlled Switching Of Shunt Reactor

With the fast development of electric power industry in china, the scale and capacity of the electric power grid is bigger and bigger, and the voltage grade gets higher and higher. Shunt reactors are usually equipped at one end of transmission lines to provide inductive reactance to compensate for the effects of high charging current of long transmission lines and limit the switching overvoltage. As the shunt reactor is the inductive load, it will produce inrush current, overvoltage and other transient phenomena during frequent switching. It's harmful for the electrical equipment and the operation of the power system. The traditional methods which are used to suppress the transient phenomena can only solve the problems to some extent, but also increase the operational complexity and the cost of the investment. The introduction of the controlled switching becomes a new way to solve the problems fundamentally.According to the different character of the load, the circuit breaker is controlled to open and close at the optimum angle of the current or voltage by the controlled switching technology. Typically, it's closed at current zero-crossing time. And when it's opened, the controlled switching controls the arc time and makes sure the contact can withstand the recovery voltage when the current's natural zero crossing occurs. Controlled switching is commonly used to reduce switching surges and gets good results. The main contents of this paper are composed of the mechanism of inrush current and ovenvoltage occurring in shunt reactor, controlled switching strategies of shunt reactor, shunt reactor modeling, and the software and hardware design of the synchronous control system. The obtained results in this thesis supply references for the practical application.Shunt reactors are relatively frequently switched. At closing, high unsymmetrical currents with long time constant can occur. During opening, interruption of small inductive currents will cause overvoltages. Resignations between the circuit-breaker contact gap can lead to very steep overvoltages that represents a special problem. The application of controlled switching can restrain the electromagnetic transient performance. Build a electric power grid including the shunt reactor. Meanwhile, the detailed simulation analysis is carried out when the system acts at random points or the target point. The simulation results reveal that controlled switching of shunt reactor is useful for the system. It's provided the support for the implementation of controlled switching by the development of digital signal processing DSP. Here the design of software and hardware for synchronous control system of permanent magnetic actuator, in which the digital signal processor DSP2182 is used as the system control centre. This system can collect the electric signals from" the power system, and calculate the zero crossing of the reference signal after the procession by the digital filter FIR. Then it makes the circuit breaker open or close in an ideal phase in order to reduce the transition impact. The results of the controlled switching system experimental test show that the accuracy of circuit breakers meets the international standards.