In order to accurately detect the beginning and end time of transient fluctuation,the voltage signal is decomposed into intrinsic mode function(IMF) elements by EMD,and then,their Hilbert spectrum are calculated.

• 应用研究表明,对暂态闪变信号进行EMD分解,再对得到的各IMF分量求HHT谱,可以精确地检测到暂态电压波动发生的时刻和终止的时刻;