基于小波变换接地故障选相判据的改进

研究了目前基于小波变换的故障选相判据，发现在发生接地故障时，由于没有考虑线模、零模的不同传播速度和不同衰减情况，无法准确确定故障相。提出了一种改进判据．首先用有无零模分量判断是否发生接地故障；对单相接地故障，进一步用线模间的关系进行选相．不再考虑零模分量大小；对两相接地故障，利用故障相电流分量突变量大于非故障相电流分量的突变量，运用已有的线模分量判断故障相。编制了相应的程序。算例仿真结果显示．改进判据对各种短路类型均能作出正确选相。

Improved criteria of grounding fault phase selection based on wavelet transform

Current wavelet transform-based criteria of fault phase selection is studied and it is found that,the grounding fault phase can not be determined because the different propagation velocities and attenuations of line model and zero model are not considered. An improved criteria is put forward,which decides first if there is grounding fault according to zero model component. For single-phase grounding fault,only the relation among line models is used to select the fault phase. For dual-phase grounding fault,the line model components are used to select the fault phase according to the fact that the sudden current change of fault phase is bigger than that of non-fault phase. Corresponding program is developed. Example shows that the improved criteria is effective for all kinds of short circuit faults.