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Main >> Applications >> Sample problems >> Electric field stress in the transformer oil

Electric field stress in the transformer oil

QuickField simulation example

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.
Electric field stress in the transformer oil Three phase transformer 3D model for electrostatic simulation A B C High voltage High voltage High voltage Low voltage Low voltage Low voltage Core Oil Insulation
Three phase transformer connection scheme Y-Y Electric potential is distributed linearly along the coil height: maximum value is at the top, zero value is at the bottom of the winding. HV LV A B C a b c

Given
Relative permittivity of oil εr = 2.2,
Relative permittivity of pressboard εr = 4.5,
High voltage (phase) V = 6 kV (RMS).
Low voltage (phase) V = 0.4 kV (RMS).
Tank, core are grounded (zero electric potential).

Task
Calculate the electric field stress distribution in the oil.

Solution
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).

Results
Electric potential distribution along the windings:
three phase transformer: electric potential distribution along the windings

Electric field stress in the oil (coils, core are hidden):
three phase transformer: electric field stress in the oil