In view of the low time-frequency resolution and large computational complexity of multiresolution generalized S-transform（MGST）

an S-transform based on Blackman window and window width ratio（BST） and its fast algorithm（FBST） are proposed in this paper. The Blackman window width function is used in BST. Compared with the Gauss window used in MGST

BST has better time-domain resolution. Moreover

in the BST

the window width ratio is adopted to control the window width

which can get rid of the control of frequency over window width. In the analysis of high-frequency disturbances

BST can maintain better time-frequency resolution. Therefore

BST is more suitable for power quality analysis than MGST. Firstly

the optimum window width ratio is determined by setting conditions. Next

the spectrum is obtained by the Fast Fourier Transform. And then noise reduction is used to eliminate the peaks caused by noise in the spectrum

so as to determine the frequency range of the signal containing information and better preserve the integrity of the information. Lastly

according to the determined frequency range

the frequency spectrum of BST in corresponding frequency range is calculated

which further improves the resolution in frequency domain. The simulation and field data analysis show that FBST can be adopted to extract time-frequency characteristics more accurately. Therefore

FBST can meet the needs of industrial accuracy and timeliness.