Design of High Voltage Transformer Windings Withstanding Surge Voltages

Abstract

High voltage windings of high power transformers, have to be designed in such a way as to withstand surge voltages. From this point of view, interleaved windings have the better behaviour, but they are much more expensive with respect to continuous ones. Thus, designers and manufacturers try to use a number of interleaved section pairs as smaller as possible, located at the top of the winding. The choice of the more proper number of interleaved section pairs can be carefully made only if the mathematical model of the phenomenon is known. In the paper a mathematical model is proposed having the goal to determine the voltage-time distribution along a disc winding of a transformer, suitable for PC implementation. It takes into account not only series and ground capacitances but also resistances and inductances of winding sections. In this way, the determination both of the initial voltage distribution and of the following local oscillations is possible. The proposed model has been validated by the good agreement between theoretical and experimental results.