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Electric field stress in the transformer oil

electric field stress in the oil, oil-filled power transformer

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

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