Problem description:
Plane electrostatic in concentric 3 phase cabel.


Geometry of the cabel:

diameter of the cabel with insulation 20mm(for all cabels)
diameter of the cabel 16mm

material parameters:
voltage  Um=9.8kV
         Eor=3
         for isulation Eor=3.3


Another parameters:
        voltage outside of the cabel U=0
        first cabel voltage          Um=9.8kV (transfering)
        second cabel voltage         1/2Um
        third  cabel voltage        - 1/2Um
Problem is plane strength,potential in cabel and in insulation.