基于粗集理论的小电流接地系统故障选线

分析了小电流接地系统中基于小波包的故障选线方法工作原理，证明了在故障线路暂态零序电流信号采样后能量损失较大时，该方法失效。为了克服该方法的局限性，提出了一种基于粗集理论的改进故障选线方法。将提取的暂态零序电流故障特征作为条件属性，信号增强倍数作为决策属性，构成一个决策系统。通过对决策表的约简，得到决策系统的最小决策算法，从而实现信号增强。再利用小波包变换对增强的信号分解，实现故障选线。ATP-EMTP仿真表明，该方法有效地提高了小电流接地选线的准确性。

Fault Line Detection Based on Rough Set Theory in Indirectly Grounding Power System

The principle of the fault line detection method based on wavelet packet transform is analyzed. It is showed that the method is invalid when the energy-loss of the sampled transient zero sequence current signal of fault line is large. In order to overcome the limitation of the method, an improved fault line detection method based on rough set theory is presented. The extracted fault characteristics of transient zero sequence current is looked as condition attributes and the multiple of signal enhancement is looked as decision attribute. So the decision system of fault line detection is constructed. After decision table reduction, the minimal decision rules can be obtained and the rules will be used to perform signal enhancement. The enhanced signal can be decomposed by wavelet packet transform to realize fault line detection. The ATP-EMTP simulations indicate that this method has effectively raised the accuracy of the fault line detection in indirectly grounding power system.