calculate the electric field near a pylon

Hi everyone,

I just started using COMSOL and I could use some help.

I would like to compute the electric field near a pylon caused by 6 conductors.
I set up the 6 conductors with a potential: u*sin(100*pi*t).
The pylon itself is ground.

A cylindrical geometry is placed over the whole pylon to define the air.

Now I would like to do a time dependent study. This works well until i set up the cylindrical geometrie as a infinite element. I tried a lot of iterative solver, but they all wont converge to one value.

can anyone help me to fix this?

thanks in advance.