Analysis of overvoltages in windings of power transformers protected by use of metal oxide surge arresters

Electrical devices are protected against overvoltages by the usage of metal oxide surge arresters. The issue of the paper is an analysis of overvoltage risks of internal insulation systems of transformers protected by such arresters. The analysis is based on the results of computer simulations of overvoltages made by using of a mathematical model of a system: the transformer-surge arresters. The model of the system includes the choser mathematical model of surge arresters and the numerical model with lumped parameters of the transformer windings. Parameters of the models are frequency dependent. Calculations were made for lightning and switching overvoltages. The results of simulations were compared to the results Of calculations for the transformer protected by use of lightning art-esters. Copyright (C) 2008 John Wiley & Sons, Ltd.