Research Of Monitoring Ways To Electric Power Transient And Harmonic Signal Based On The Wavelet Transform

Based on the characteristic of five common power transients(namely voltage sag,voltage swell,voltage interruption,surge and impulse) and the old method of power quality analysis, this paper adopts a novel digital signal processing method-the wavelet transform according to the non-steady characteristic of power quality transients.The good time-frequency location of the wavelet transform makes the sigularity of signal can be signified as the wavelet transform modulus maxima.Using Mallat algorithm,the wavelet transform modulus maxima of singularity is extracted through multiresolution decomposition.By which,the accurate localization of fault signal can be realized,the duration and amplitude of which can also be obtained.To conquer the old wavelet inherent shortcoming,a combine wavelet is designed and used to realize the accurate detection to harmonic contents and frequency of power quality transient signals. To satisfy the real time processing requirement of electric power transient protection by optical current transducers , a quadrature double paths optical current transducer's system is constructed and the real time detection to the power quality transients' signal has been done by the wavelet transform. The simulation results have verified the validity of this method.