The transformer is submerged in the oil. The windings are insulated by the oil-impregnated paper. We need to locate the places with high electric stress (in addition to the well-known areas between windings and between windings and core).
Problem Type: electrostatics.
Geometry: 3D extrusion.
Relative permittivity of oil εr = 2.2,
High voltage (phase) V = 6 kV (RMS).
Low voltage (phase) V = 0.4 kV (RMS).
Tank, core are grounded (zero electric potential).
Calculate the electric field stress distribution in the oil.
We simulate the static problem (fixed moment of time), when phase A has maximum electric potential V*cos(0°), potentials of the phases B and C: V*cos(120°) and V*cos(240°) respectively. Electric potential is distributed linearly along the coil (maximum value is at the top, zero value is at the bottom of the winding).
Electric potential distribution along the windings:
Electric field stress in the oil (coils, core are hidden):