STUDY ON EDDY-CURRENT LOSSES AND SHIELDING MEASURES IN LARGE POWER TRANSFORMERS

The improved T-OMEGA method is applied to the computation of the three dimensional eddy current field in a 360MVA/500kV large power transfor mer, the structure of which is complicated. The different cases of tan k wall with magnetic shunt, aluminum screen or without any shield are analyzed. The relations between eddy current losses and the materials, structure and size of the tank shield are presented. Compared with a parallel magnetic shunt arrangement, the vertical magnetic shunt reduc es stray losses by 63.8%. The optimal thickness of the vertical magnet ic shunt is 10mm. The magnetic shunt should be spread over 0.5mm at bo th ends of windings in the 360MVA/500kV large power transformer.