Nonlinear equivalent circuit model of a traction transformer for winding internal fault diagnostic purposes

The paper presents the development of an equivalent circuit model of a traction transformer intended for studies into the diagnostics of interturn faults. The model accounts for the nonlinear B-H characteristic of the transformer core. The derivation of the model is based on the Lagrange´s energy method. The values of model parameters were evaluated by means of 3D finite element model computations. The simulation studies based on the proposed equivalent circuit suggest that interturn faults can be detected by evaluating transformer losses.