Comparison of the Use of Wavelet Transform and Short-Time Fourier Transform for the Study of Geomagnetically Induced Current in the Autotransformer Neutral

A large amount of data has been recorded and accumulated by the registration system of geomagnetic disturbances in the Kola power grid for many years (from 2011 to the present). The measuring devices of this system are installed in dead-grounded neutrals of autotransformers at a number of substations in the North-West of Russia (in the Murmansk region and Karelia). The article compares the analysis of the current in the autotransformer neutral using the short-time Fourier transform (STFT) and the wavelet transform (WT). A discussion of the spectrograms and scalograms of both data processing methods is given on the example of the geomagnetic storm analysis that occurred on September 7-8, 2017. The geomagnetic storm was significant and the value of the geomagnetically induced current (GIC) reached 78 A these days. During the research, the most appropriate method for analysing the GIC was selected - continuous wavelet transform.