长数据窗算法的动态特性及其在快速保护中的应用

摘要

当保护所采集的电气量发生跃变时,算法的数据窗内同时包含跃变前、后的数据,算法输出结果所呈现出的动态特性一般不具有单调递变性质,这就限制了长数据窗算法在快速保护中的应用,必须靠整数据窗延时躲过动态过程.然而理论分析表明,当跃变前电流为0时,通过全周傅里叶算法计算得到的电流幅值,在动态过程中均不大于完全采用跃变后数据计算的电流幅值,因此采用长数据窗的全周傅里叶算法在动态过程中的输出结果仍可用于某些快速保护.基于上述分析,设计了利用长数据窗算法动态特性的快速差动速断保护方案,在提高保护速动性的同时,避免了复杂的长短数据窗算法的切换.理论分析和仿真验证表明,所提快速保护方案有效、可靠,在不采用短数据窗算法的情况下,仍可获得良好的速动性.%When the electrical quantities collected by protective relay suddenly change,the data-window of a algorithm contains both the data before and after the jump,so generally the dynamic characteristic of the algorithm does not increase or decrease monotonically,which limits the application of long data-window algorithm in instantaneous trip protection.The problem can be solved by the whole data-window delay.However,theoretical analysis shows that if the current is zero before the jump,the current amplitude calculated by whole-cycle Fourier algorithm during dynamic process is always less than the amplitude entirely calculated with the data after the jump,so the output of whole-cycle Fourier algorithm during dynamic process still can be used in instantaneous trip protection.Based on the above analysis,a fast differential instantaneous trip protection scheme using the dynamic characteristic of long data-window algorithm is designed,which can improve the rapidity of differential protection and avoid the switch between long data-window algorithm and short data-window algorithm.Theoretical analysis and simulation verify that the proposed scheme is efficient and reliable,it can achieve outstanding rapidity without using short data-window algorithm.