Stress control for cable termination - QuickField simulation example
33kV single core cable termination has design measures to control the electric stress near the screen end. Special mastic with a field-dependent electrical conductivity is used.
How to find electric stress control in cable termination?
Answer Typical applications Geometry
Given
Task
Solution
To improve convergence we added two points to the end of the curve to artificially limit the conductivity value at extremely high electric field stress: [54 kV/mm, 14 pS/m], [73 kV/mm, 15 pS/m]
Results
Engineering question
Set up an axisymmetric QuickField Transient Electric problem for a cable termination and evaluate electric stress control from computed field results.
medium-voltage cable terminations, stress control tubes, cable termination accessories
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Simulation problem
Problem Type
Axisymmetric problem of transient electric.
AC frequency f = 50 Hz, conductor potential V = 33 kV (r.m.s.).
Screen potential - 0 V (grounded).
XLPE permittivity 2.5.
Insulation materials electrical conductivity 1e-15 S/m.
Yellow mastic permittivity is 15, electrical conductivity is field-dependent:
Calculate the effect of electric stress reduction.
To represent sinusoidal varying electric potential we can use the equation: V*sqrt(2) * cos(360° * f * t).
In fact we are interested in the peak stress values, so we can apply peak voltage value of V*sqrt(2).
Later the results revealed that the electric field stress is within the limits of the original data.
With a stress control mastic the maximal electric stress along the insulation surface reduces from 58 kV/mm to 25 kV/mm.
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