Research On Prebreakdown Characteristics Of Vacuum Circuit-breaker With Permanent Magnetic Actuator

This text introduce prebreakdown characteristics of vacuum circuit-breaker with permanent magnetic actuator. It bases on a practical project in power system.First, this text analyses the mechanism of breakdown of vacuum circuit breaker. The experiments were carried out under AC and DC. The prebreakdown characteristics of vacuum circuit breaker are derived from the experiments, then fitting the calculation results of the electric strength in the vacuum interrupter. It is found that the dependence of breakdown voltage on the gap length at short distances is nonlinear, and it is different from the static breakdown characteristics. In the other hand, it is also found that the dielectric strength of breaker would decrease if the closing velocities exceed a certain critical value. And in the same contact gap conditions, the ac dielectric strength of vacuum gap is equal of dc.Secondly, because of the effect of closing time dispersion on prebreakdown characteristics, and the dispersion of actuator and controlling signal make the action dispersion. The BP neural network and adaptive method are used to compensate the actuator time in real time environment (temperature and control voltage) to reduce the dispersion; pick the high accurate electronics will reduce the dispersion of controlling signal; and derive the most suitable closing phase under considering the prebreakdown characteristics.Finally, this text used the experiment data that has been gained in chapter 3 to train and establish a BP neural net. The establishments of the model have the precise relationship of breakdown voltage and its gap length.