The power transformers are one of the most valuable and important component of the power electric system. Due to the high price it is a long-term investment. It is hardly necessary to emphasise the importance of a reliable insulation system to the power transformer.
The main topic of this master thesis is related to insulation system of large power transformers. Firstly, it is described to the theoretical background of the transformer, and after it is described to the insulation materials and the diagnostic methods of insulations.
The practical part is related to a current project. The electrical stress of insulation systems is related by finite element methods (FEM) which is a modern way of computer-aided design.
At the lead exit area of windings are calculated some two-dimensional models by two FEM softwares. It is created a three-dimensional model using by the model of cratch and insulation of winding drawing. This way, the results of simulations of different finite element softwares are compared.