Influence of temperature on the transfer function (TF) of power transformer windings

Although the transfer function (TF) method is widely used to detect deformation and displacement of power transformer windings, the sensitivity to minor defects is affected by several factors. This paper presents the influence of temperature on the TF of transformer windings. Nanosecond pulse was used to extending the frequency band of the measurement system. The experiment was carried on a purpose-made laboratory winding and TFs with different temperature were compared. And the relative permittivity of Oil and paper of different temperature were tested to interpret the measurement results. In order to compare the sensitivity to temperature and winding deformation, minor axial deformation was modeled. Experiment results showed that TF changed with the temperature, especially in the high frequency range. The temperature may reduce the detect sensitivity to minor deformation.