Lighting impulse voltage distribution vs. transformer insulation design

in this paper is presented a method of modeling the transient phenomena which occur in power transformers winding during lightning impulse voltage test. From the modeling point of view the power transformer winding is without iron core. The equivalent circuit diagram and its parameters (equivalent capacities, self and mutual inductances, conductance and electrical resistances.) are determined using methods depending on transformer electrical characteristics and geometry. In the last part of the article there are presented a series of modeling and measurements results performed on a autotransformer.