Analysis on the flux leakage distribution by the 3D FEM simulation method under the different local and minor transformer winding defects

The transformer winding local deformation and minor inter-turn short-circuit always induce the distortion of the magnetic flux leakage characters, and monitoring the flux change is the only feasible and valuable method to diagnose the local and minor winding defects online. The paper specifically describes the correlation between the flux leakage and different winding defect by the means of the 3D simulation, which is the key to achieve the method. The 35kV three phases transformer was simulated as the full-scale model with different winding defect, including the external radial winding deformation and minor inter-turn short-circuit defect. Then, the magnetic field norm and vector were analyzed respectively, and explore the distribution difference in the different defect levels, the monitoring points. As the result, the magnetic field distortion of different places under the local radial deformation has no simple negative correlation related to the distance between the monitoring point and defect center. Additionally, the local flux leakage distortion around the inter-turn short-circuit coil decreasing sharply, because of the huge inverse induced current.