The Hilbert–Huang method is presented with modifications,

for time-frequency analysis of distorted power quality signals.

The empirical mode decomposition (EMD) is enhanced with

masking signals based on fast Fourier transform (FFT), for separating

frequencies that lie within an octave. Further, the instantaneous

frequency and amplitude of the constituent modes obtained

by Hilbert spectral analysis are improved by demodulation. The

method shows promising time-frequency-magnitude localization

capabilities for distorted power quality signals. The performance

of the new technique is compared with that of another multiresolution

analysis tool, the S-transform—a phase corrected wavelet

transform. Analysis on actual measurements of transformer inrush

current from an existing laboratory setup is used to demonstrate

this technique.