Abstract. The article the possibility of applying the wavelet transform method in combination with a neural-fuzzy approach to solving problems of forecasting the state of digital substations is considered. The optimum level of the wavelet expansion of the time series corresponding to the change in the phase voltage for the day on the basis of the Hurst index is determined. The influence of the sample size and the type of the mother wavelet on the Hurst index is researched. It was revealed, that for wavelet decomposition, the use of the Daubechy wavelet as the mother wavelet is effective, which provides a smoother filtering of noise, compared to the Haar wavelet. Analysis of the original series does not allow to evaluate the optimal level of wavelet expansion if the noise level of the time series under consideration is low (less than 10%), since the Hurst index remains unchanged. However, using the logarithm of changing the time series allows for small fluctuations to be taken into account, which allows to determine the optimal level of the wavelet expansion for their smoothing.
This article is devoted to the development of a mathematical model for determining the electromotive force (EMF) of the secondary winding of a measuring current transformer based on a Rogowski coil. The study focuses on determining the EMF in the secondary winding of the current transformer at different positions of the primary bus, its forms, as well as the overall dimensions of the whole measuring equipment. The study was conducted on the basis of finite element modeling and elements of the experimental design techniques. Finite-element models have been developed for various primary bus shapes in the Femm program. Regression models were obtained for determining the magnetic flux passing through the Rogowski coil in order to determine the EMF in the secondary winding using the Statistica program. The research results showed the importance of taking into account the position of the primary bus relative to the center of the Rogowski coil, as well as the influence of the shape of the primary bus on the measurement result of EMF in the secondary winding of the current transformer.
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