Study of transformer winding deformation by frequency response analysis

This paper proposes a methodology to interpret frequency response measurements of a deformed transformer winding due to conductors tilt. To achieve that, geometrical parameters of a three phase prototype transformer is used to simulate the frequency response of one of the windings using the multi-conductor transmission line model. To simulate the response, inter-turn, inter-disc and inter-winding capacitances of the winding based on normal and deformed conditions are computed using finite element method. Using the computed values, the frequency response for both normal and deformed conditions are simulated. The simulated responses are studied by subdividing into four frequency regions and compared using the correlation coefficient. For further analysis, the vector fitting algorithm was implemented to approximate the transfer function of each response. All transfer functions are then represented in the Nyquist diagram to analyse the shape of each plot. From the Nyquist diagram, it was observed that the real minimum of each plot increases as the winding deformation increases. This finding can be used to estimate the winding deformation severity based on the plotted attributes.