Research On Restraining Operation Overvoltage By Synchronous Switching For UHV Transmission Line

Because the characteristics of China's energy structure and distribution, construction of ultra high voltage(UHV) transmission lines has become an important direction for industrial development. Operating overvoltage level determines the insulation design of UHV lines. Requirements of operating overvoltage level for UHV is more stringent than EHV. So overvoltage and it's restrain method should be studied deeply.The thesis analyzes the mechanism of some kinds of overvoltage and describes their restrain method, such as such as circuit breakers with pre-insertion resistors, MOA(metal surge oxide arresters), shunt reactors, and synchronous switching technology. In recent years, synchronous switching technology has been more widely used. In this thesis, the feasibility that controlled switch technology is applied to restrain operating overvoltage on UHV has been verified. And some synchronous switching strategies for closing unload line are presented.EMTP-ATP is a widely used software electromagnetic transient simulation software. Overvoltage, the effect of it's restrain method and synchronous switching strategies are simulated by EMTP-ATP. Then it comes to a conclusion that the effect of synchronous switching strategies is better than traditional methods.Synchronous switching requires a tiny deviation of operating time of circuit breaker. FCVIM(Fiber-controlled vacuum interrupter module) based on permanent magnetic actuator can meet this requirement. Series or parallel connection of many FCVIMs can reach a higher breakdown voltage, it's a new way to solve the synchronous switching used in UHV lines. Here, the design of software and hardware for synchronous control system of permanent magnetic actuator, in which the digital signal processor TMS320LF2407A is used as the kernel, is presented. This system apply synchronous switching theory. It collects real-time network signals to control circuit breakers operating in the best phase point. Test results show that the operation of prototype device is stable and reliable, the prospective design specifications are implemented.