Study On Wave Process And Resonance Of Transformer Windings Under Very Fast Transient Overvoltages

Multi-conductor Transmission line (MTL) model based on the representation of the winding by its individual turns is used to analyze the transient response of transformer windings under Very Fast Transient Overvoltages (VFTO). A very efficient method, the simplified finite element method is used to compute the elementary parameters of transformer winding. For a real transformer winding, if each turn is simulated as one transmission line, a system of very large-scale equations will be obtained. This paper presents a model based on MTL using equivalent impedance to simplify the calculation. The single input and multiple output (SIMO) system is presented to calculate the transfer function. The resonant frequency and locations are obtained by this method. A new method to calculate the transient response of transformer via vector fitting and recursive convolution is also presented to solve the inevitable flaws of FFT. For validation, the calculated results are compared with the measurements on a transformer winding model and the result is satisfactory.