Determination of a capacitance model for inductive medium voltage transformers
To increase the linear frequency range of inductive medium voltage transformers, the calculation of its frequency response will be the first step. For this several capacitances have to be known, such as the layer, the ground and the front part capacitances. For the calculation of these three most important parasitic capacitances mathematical models based on measurements of medium voltage transformers are developed. With the resulting equations, capacitances can be determined without a complicated three-dimensional field calculation. For the modeling of layer capacitances it is possible to fall back on the equation of cylinder capacitors which is completed by two correction factors. These are determined and verified by measurement on different voltage transformers. For the ground capacitance a simple equation is introduced, inspired by established equations for capacitance calculations. By means of measurements the required initial value is determined and the model for the ground capacitances is verified. Finally, the front part capacitances are described with a theoretical model, which is based on a simple field-theoretical approach.