Short Circuit Stress Analysis in Power Transformer Using FEM

The objective of this work is to compute the mechanical stresses within transformer resulting from the excessive short-circuit currents. The forces and stresses set up in transformer windings and their clamping structures, as the result of external or internal short-circuits or of switching operations, are considered in detail. Various arrangements of windings in large power transformers are described. Points at which particularly high mechanical stresses occur in concentric windings are discussed in detail. Analytical and FEM (Finite Element Method) calculation for both types of short circuit forces, axial and radial have been discussed. The result was then compared with actual measurements on a prototype 20MVA 132 /11.5KV power transformer. Various failure mechanisms due to these forces have been elucidated. Axial forces between the top and bottom halves of each winding or between different windings are responsible for bending stresses in turns near the ends or adjacent to gapsin the windings, for compressive stresses in the body of the winding, and for tensile and compressive stresses in the clamping gear. Radial forces produce tensile stresses in the outer and buckling stress