Research On Controlled Switching Technology Of Vacuum Circuit Breakers

Controlled switching technology, a significant aspect of circuit breakers intelligence, is one of the most economic and effective ways to reduce inrush current and overvoltage when switching the capacitors, transformers and other power apparatus. It is a predefined controlled strategy for closing or opening each independent circuit breaker pole, and a good way to reduce electromagnetic transient effect caused by switching process. Which can improve the stability and reliability of power system.This paper introduces the background, theory, difficulty and the research actuality at domestic and international of the controlled switching technology. The conditions of switching no-load transmission line, capacitors and no-load transformer are analyzed and the switching strategy is given by building a simulation model. To overcome poor anti-interference ability and temperature drift of the traditional analog voltage comparator, an interpolation algorithm based on FIR digital filter is proposed to obtain zero-crossing point. The plural Fourier transform algorithm is applied to the electric parameter measurement and harmonic analysis, which makes the circuit breaker have a digitized monitoring function. Considering the measurement error of the nonsynchronous sampling, an adaptive Fourier algorithm based on high sampling rate and fixed-frequency sampling is proposed. The simulation results show that the algorithm is accuracy and reliability when frequency fluctuate.Finally, the hardware and software realization technology of the controller is researched and the control circuit based on digital signal processor DSP28335 is designed. The control circuit includes master control circuit, analog signal input circuit, switching I/O module and humaninteractive module, which can implement the monitoring, protection, communication and intelligent controlled switching function.