Research On Forecast Method Of Current Zero-cross Points For Controlled Fault Interruption

Short circuit fault is a common fault in power system.Because of the decreasing impedance of power supply circuit and transient process resulting from sudden short circuit when the fault happens,the short circuit current increases greatly in the short circuit loop, even many times more than the rated current.Short circuit current seriously affects safe and stable operation of electrical equipments.Controlled switching,also called synchronous switching,has been proposed in recent years.It has been gradually used in switching of capacitor bank,shunt reactor,unloaded transformer and so on,which can eliminate inrush phenomenon and over voltage effectively.However,there hasn't been an effective solution for controlled fault interruption yet.Controlled fault interruption can reduce the contact ablation and improve some properties of circuit breakers,such as breaking capability,reliability and lifetime.So controlled fault interruption can promote the development of new breaking technology,which is the frontier topics in the field of high voltage switch in domestic and abroad at the present time.Controlled switching is a terminology applied to the principle of coordinating the instant of opening or closing of a circuit with specific target point on an associated voltage or current waveform.For controlled fault interruption,forecast of current zero-cross points is the primary task.According to the research status in domestic and abroad,this paper introduces two forecast methods of current zero-cross points and simulation analysis,which may lay a theoretical foundation for controlled fault interruption.First,this paper introduces the causes of short circuit fault and controlled switching,and also describes different types of short circuit fault and application status of controlled switching.Secondly,the scheme of controlled fault interruption is deeply researched which describes the necessary work before predicting current zero-cross points.And then this paper carries out the effects of related parameters on current zero-cross points according to setting up single phase short-circuit model.Finally,this paper discusses descriptions of safe-points algorithm and self-checking algorithm in detail,and presents the process of its realization. Based on different ways to describe fault current,this paper put up simulation analysis by two algorithms. The adaptability of the two algorithms has been discussed through simulation analysis and data processing for several times,which can provide advantageous reference for choosing suitable algorithm to achieve controlled fault interruption according to the actual need.At last, this paper concludes the research and anticipates the prospects of it.