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Cable termination to oil filled bushing

QuickField simulation example

Stress cone with deflector is used to reduce the electric field stress in the cable termination.

Engineering question
How to find electric field in cable-to-bushing terminations

Engineering answer
Set up an axisymmetric QuickField AC Conduction problem for a cable-to-bushing termination structure and evaluate electric field distribution from computed field results.

Typical applications
transformer cable bushings, cable-to-bushing interfaces, stress cone assemblies

Problem Type
Axisymmetric problem of AC conduction.

Geometry
Cable termination to oil filled bushing Stress cone with deflector are used to reduce electric field stress in the cable termination. 10 mm 0.1 mm 10 mm Dielectric (XLPE) Conductor (copper) Stress cone Oil Flange Insulation screen Semiconducting insert Deflector

Given
Voltage U = 64 kV (r.m.s.), frequency f = 50 Hz.
Relative permittivity of media: oil 12, insulator 2.3, stress cone 22, deflector 2.5.
Deflector electrical conductivity 0.0002 S/m.

Task
Calculate electric field stress distribution.

Solution
Semiconductors are modeled as materials featuring both electric permittivity and conductivity, though small.
In QuickField we should specify the magnitude of the time-harmonic voltage that is room mean square value times square root of two: 64000*sqrt(2).

Results

Electric field stress distribution in the cable termination
Cable termination to oil filled bushing

Reference:
Simon Dubitsky, George Greshnyakov, Nikolay Korovkin Optimization of Capacitive and Resistive Field Grading Devices for Cable Joint and Termination. INTERNATIONAL JOURNAL OF ENERGY. volume 9. 24-30.