ABSTRACT
This chapter shows that a number of accurate methods are reported in the literature for the computation of the response of the windings to voltages. For designing the insulation system of a transformer for withstanding overvoltage tests, voltage stresses within its windings need to be determined. For this purpose, voltage distributions within the transformer windings for the specific test voltages are calculated. When a step voltage impinges on the transformer winding terminals, the initial distribution in the winding depends on the capacitances between turns, between windings, and those between windings and ground. In order to estimate the voltage distribution within a transformer winding subjected to impulse overvoltages, the knowledge of its effective series and ground capacitances is essential. The principle of electrostatic shielding is regularly used in the form of static end rings at the line end of high voltage windings and static rings within the windings, which improve the voltage distributions and reduce the stresses locally.
