Capacitive weighting technique for estimating the 3D turn-level capacitance in a transformer winding

An alternative method to calculate the low frequency capacitance between transformer turns for use in multi-conductor transmission line modeling (MTL) of transformers during high frequency transients is presented. This paper makes use of both 3D and 2D finite element simulation to more accurately calculate the capacitances than can be done by closed form equations with simplifying assumptions while avoiding the computational difficulties involved in the three dimensional analysis of a transformer on the turn to turn level. The method is demonstrated on an arbitrary transformer with few enough turns to readily compute 3D turn-level capacitance for comparison. It is then applied to a real transformer. The results are used to calculate the terminal capacitance which is compared to experimental measurement and found to be within 5% of the measured value.