Jim, K7JEB, wrote:
....
Again, this is just a special case of the general
problem. But it has a configuration that is easy to
implement in the EZNEC program and is quite
relevant to typical ham-radio, low-band dipole
installations.

It's also easy to get the electric field strength near the antenna from EZNEC.
I expect the field to be highest near wires, because of the shape the field
must take near the wires, so that's where I'd look first to get an idea about
possible breakdown of the air or insulators.

Cheers,
Tom