Transformer high current lead arrangement

Generator transformers have losses in the structural parts besides that due to stray fields from windings also due to high current leads. High current leads can cause high stray losses and/or high temperature rises. In this paper an overview of the advantages and disadvantages of different leads arrangement is given. Using a 3D FEM software, calculations for eight different leads arrangement are done on a model of a 220 MVA transformer with phase current of 4, 4 kA. A model with no leads, model with lead of Y-connected windings, five different arrangements of one layer winding in delta connection and a model of two-layer winding in delta connection were analyzed. Total losses and loss densities were analysed for each model. The influence of tank shields height on loss densities and loss level is considered.