In addition, line mode and zero-mode voltage wave cross each other at the pointoffault which causes the natural frequency "aliasing".
此外，故障电压行波于非对称短路点发生线模与零模行波相互交叉透射，致使故障电压自然频率“混叠”。
2
Sag state estimation observability analysis is modeled and correlative modification method is proposed from the pointoffault current superimposing firstly.
In pointoffault prediction, neural network based combination prediction is studied in the paper in which the best combining of traditional prediction methods is given by neural network.