Introduction of dimensional approach to evaluation of distribution transformer short circuit forces

In this paper the radial and axial forces developed under windings short circuit conditions in two different designs of a 630 kVA distribution transformer (using analytic and finite element method) are determined and compared. The simulation results using FEM software verify the results of the employed analytic method. These results show that although the transformer with larger dimensions have a better operating performance and lower total owning cost with respect to one with smaller sizes (assuming the same mechanical strength for winding and support structures of both), the risk of failure due to its related short circuit forces elevates in the former. Additionally, this paper presents some analytical expressions which demonstrate the relationships between short circuit forces and transformer geometrical parameters. These relationships help transformer designers to choose the best dimensional parameters to improve the transformer performance in such a way that risk of failure of transformer due to short circuit forces doesn´t increase or increase in a lower paste if compared with the other sample.