电流互感器的暂态仿真及其铁芯饱和的小波分析

TRANSIENT SIMULATION OF CURRENT TRANSFORMER AND WAVELET ANALYSIS OF ITS CORE SATURATION

在用多项式拟合电流互感器 (CT)铁芯磁化曲线的基础上对 CT暂态过程进行了仿真 ,较好地刻画了 CT的暂态过程 ,有利于对电流互感器进行合理的设计和参数的优化。电力系统母线发生区外短路故障时 ,电流瞬时值母线差动保护易受 CT铁芯饱和的影响而误动作 ,文章提出了一种基于小波变换的 CT二次电流波形分析方法 ,同时将 Hilbert变换运用到 CT铁芯饱和时刻的定位中 ,比较精确地检测出了CT饱和的时刻。利用在母线发生短路故障时 ,每周波前 1/ 4周期 CT铁芯不会发生饱和的特点 ,结合一个周波内二次电流的第一次过零点 ,可以较好地实现在

On the basis of fitting magnetization curve of core of current transformer (CT) by polynomial, the transient process of CT is simulated, this method depicts the transient process of CT better and is beneficial to the structure design of CT and the optimization of its parameters. When external short circuit fault of bus occurs, the bus differential protection with instantaneous current value often maloperates because it is easily influenced by the saturation of CT's core. A wavelet transform based analysis method for the wave of secondary current of CT is proposed, at the same time, the Hilbert transform is applied to determine the moment when CT's core saturates, thus, the moment of CT being saturated can be examined more accurately. Using the characteristic that at the front part of each period the core does not saturate and combine with the first zero cross point of the secondary current in a period, it can be well implemented to open differential bus protection in the linear region of CT.