带并联电抗器输电线路拍频电流幅值分析

Analysis of Beat Frequency Current Amplitude of Transmission Lines with Shunt Reactors

目前在自适应单相重合闸中缺乏对拍频电流表达式、拍频电流是否一定存在及其幅值范围的研究。单相瞬时性故障消失后,拍频电流不存在或过小,都会影响重合闸判定的可靠性。拍频电流受健全相电压和故障消失后线路中元器件初始状态的影响,采用叠加原理得到完整的拍频电流表达式;通过分析表达式得出最小拍频电流及其出现的条件,分析出拍频电流为零属于小概率事件;拍频电流受故障时刻、故障持续时间、电弧电阻、电源相角差及故障位置等共同影响,使得不同工况下的拍频电流差异明显,若幅值过小,将会影响重合闸判定的可靠性。文中利用正交实验的方法给出某500kV输电线路拍频电流幅值大小的范围,证明了在工程实践中可以用拍频电流实现自适应重合闸。

At present,researches on the adaptive reclosure lack an analytic expression for beat frequency current about whether the beat frequency current definitely exists and the range of amplitude of the current in adaptive reclosure.The amplitude may be nonexistent or too small when the single-phase transient fault disappears,which will affect the reliability of reclosing determination.The beat frequency current in the shunt reactor is not only affected by sound phase voltage but also by the initial state of components of transmission line when fault disappears.Based on the superposition principle,the complete expression of beat frequency current is obtained,by an analysis of which the minimum beat frequency current and conditions for its occurrence are obtained.It is concluded that the beat frequency current being zero belongs to small probability event.The current is affected by fault time,arc duration,arc resistance,phase angle difference and fault location that make the amplitude obvious.If the amplitude is too small,it will affect the reliability of the reclosing determination.The paper gives the range of amplitude of the beat frequency current on 500 kV transmission lines using the method of the orthogonal experiment in mathematical statistics,proving the beat frequency current can be applied to engineering.