基于SAX及空间信息熵的谐振接地系统单相接地故障选线方法

Single Phase Grouding Fault Line Selection Method of Resonant Grounding System Based on SAX and Spatial Information Entropy

针对含多电缆谐振接地系统健全线路零序电流相似性减弱以及单相高阻接地因故障信息微弱且易被干扰而使选线正确率下降的问题,提出一种基于符号化聚合近似(symbolic aggregate approximation,SAX)及空间信息熵的选线方法。首先通过FIR滤波器提取暂态低频零序电流并标准化,然后将所得电流序列及其差值序列在多尺度域上符号化,通过最长公共子序列校验后生成三维故障空间并定义空间信息熵,最后比较线路间熵值差异度完成选线。仿真结果表明,所述选线方法灵敏度高,硬件要求低,能够克服采样不同步、三相不平衡等困难。

Aiming at the problem that the correct rate of line selection decreases due to the weakening of the zero-sequence current similarity of the sound line with multi-cable resonant grounding system and the weak fault information of single-phase high-resistance grounding.A line selection method based on the symbolic aggregation approximation(SAX) and spatial information entropy is proposed.Firstly,low frequency transient zero sequence current is extracted by FIR filter and normalized,and then the low-frequency current sequence and its difference sequence are symbolized on the multi-scale domain,and the three-dimensional fault space is generated after the longest common subsequence check and the spatial information entropy is defined,and finally the entropy difference between lines is compared to complete line selection.The simulation results show that the line selection method has high sensitivity,low hardware requirements,and can overcome the difficulties of sampling asynchronization and three-phase unbalance.