Modeling and Characterization of Transformers Internal Faults using Finite Elements and Discrete Wavelet Transforms

This paper examines the behavior of single phase and three phase transformers with internal faults under sinusoidal and non-sinusoidal operating conditions. The terminal behavior of the transformer was investigated by coupling the finite element transformer´s physical model and external electric circuit simulations. Such a model would allow the efficient representation of the transformers with internal faults. A discrete wavelet transforms (DWT) was then used to extract the different harmonic components of the transformer currents. The key advantages of the DWT are its ability to provide a local representation (in both time and frequency) of the current signal for normal and faulty modes, as well as its applicability to nonstationary signals