A method for modeling power transformer tap winding for transient studies

One of the challenges a transformer designer is faced with is to correctly model the different types of transformer windings for transient study. For a precise insulation design, determination of transformer transient responses is unavoidable. The basis of these studies is calculation of transient responses due to application of standard switching and lightning impulse waves to the transformer winding. In a previous work, a computer program was developed for determination of the layer and disk type windings transient model parameters based on design data. This program has all of the necessary capabilities for a detailed transient study. As a continuation of that work, A method will be introduced for modeling the transformer tap winding. The tap winding is a part of HV or LV winding in a transformer which can be used for adjusting the output voltage after any small change in the output voltage. This model will be employed for modeling a 40 MVA and 230/63 kV transformer with tap winding, and the voltage distribution along its tap winding will be employed for evaluation of the model.