Experimental and theoretical investigation of disc space variation in real high-voltage windings using transfer function method

The ability of a detailed RLC model of a winding to calculate the transfer function (TF) and to demonstrate the effects of various winding damages on TF has been proven on small laboratory windings by previous studies. However, this ability is not adequately known for real high-voltage windings. Hence, a 400 kV disc winding consisting of 86 discs is used in this work to study, whether the detailed model is able to represent the behaviour of large-power windings in a TF form. In addition, disc space variation (DSV), known as a frequently occurring mechanical damage in transformers, is analysed experimentally and mathematically. The accuracy of the model to identify the DSV is verified with the help of the measured TFs.