IMPACT OF ELECTROMAGNETIC SHIELDS ON LOCAL OVERHEATING IN TRANSFORMER TANK

Abstract

The paper describes different influences of magnetic and electromagnetic shielding on stray flux distribution in power transformers. The application of electromagnetic shields on the reduction of high temperature spots in transformer tank is studied in detail by using a 3D model for a coupled electromagnetic-thermal calculation. The analysis of transformer models with various shapes and dimensions of electromagnetic shields show which factors are the most important for reduction of temperature hot spots in the tank. Proposed shielding solution should reduce the total stray loss and maximum temperature value. It is shown that the reduction of these values is not always achieved by shielding most of the area endangered by the stray flux from the high current leads. The choice of the shield must take into account the surrounding component material properties and transformer lead arrangement.