Just to address the title of this thread a little better here is a picture of a rural 110kV distribution line in NI that runs from substation to substation.
In damp conditions this line will 'sizzle' quite loudly and the corona discharge can be seen jumping the insulators!

[Linked Image from img219.imageshack.us]

And a close up.

[Linked Image from img219.imageshack.us]

Martin.