基于中值滤波的超高速暂态量方向元件

Ultra-high-speed Transient Directional Unit Based on Median Filtering

方向元件是基于行波或暂态量的超高速方向保护的核心元件。该文提出一种新型的超高速暂态量方向元件,利用故障后很短的一段时间内前行波与反行波之间时域能量的特征差异来判别故障方向。为了凸现本质的特征差异,减小故障初始角、反射波和母线接线方式等因素的影响,同时避免小波变换多分辨率分析在数据窗、小波基选取时所面临的困难,先由具有细节保留特性的非线性中值滤波器对前、反行波进行滤波,再通过简单的平方和运算求取前行波与反行波的时域能量之比来判别故障方向。大量ATP仿真试验表明,该方向元件能可靠、灵敏、超高速地动作,性能稳定,方向性明确,运算量小,对于各种故障情形、系统结构的适应性很强。

Directional unit is the kernel unit of the traveling waves or transients based ultra-high-speed directional protection for transmission line. A novel ultra-high-speed transient directional unit is proposed, which identifies fault direction by means of comparing the time-domain energy of the forward traveling-wave with that of the backward one in the very short period of time after fault occurs. In order to stand out essential feature difference, decrease the influences from low inception angles, reflective traveling-waves, feeder modes on bus-bar and so on, and also avoid the difficulties of wavelet multi-resolution analysis, the nonlinear median filter with fine detail preserving characteristic is first employed to process the forward and backward traveling-waves, and then calculates the time-domain energy ratio of the forward traveling-wave to the backward one, by which the fault direction is discriminated. A number of ATP simulation tests show that this novel directional unit not only operates reliably, sensitively and very fast, but also possesses stable performance under various fault situations and system structures.