基于小波变换的电流互感器饱和实时检测新判据

目前微机母线保护最常用的方法是电流瞬时值差动保护。这种方法受电流互感器（TA）饱和的影响而容易误动作。一种解决的方法是当TA饱和时闭锁母差保护。但该方法当故障由区外转为区内时保护会拒动。文中利用小波变换能检测信号奇异性的原理，提出了一种实时检测TA饱和区和线形区的一种新方法。在故障开始后对TA二次电流实时进行多尺度小波变换，由于TA二次电流波形在故障发生时刻、进入饱和时刻和出饱和时刻都有奇异性，分别对应小波模极大值，可根据小波模极大值的不同特征判断对应时刻的是进饱和点还是出饱和点，从而实现TA饱和区闭锁、线形区开放的母差保护。

A NEW ON-LINE CRITERION FOR CURRENT TRANSFORMER SATURATION BASED ON WAVELET TRANSFORM

The bus differential protection based on instantaneous values of currents is the m ost useful schem e nowadays.But it is easy to be influenced by currenttransformer saturation and to m ake mal- operations.One of solutions is to block the relay when current transformer is saturating.But this method can m ake the relay refuse to trip when a fault transfers to inside the protected zone from outside.In this paper,a new method is proposed to detectand distinguish currenttransformer saturation and linear sections,and the wavelet transform theory is used to detect the singular points of signals.Because the current waveforms got from current transformer have singularity atthe points of faultoccurrence,the startof saturation and the end of saturation,we can distinguish these points according to their characters on- line.Thus,to open or block it in current transformer linear or saturation sections,the bus differential protection can be realized.