In article ,
The Natural Philosopher writes:
PCPaul wrote:
http://www.youtube.com/watch?v=PXiOQCRiSp0

Thiose isolators are NEVER opened under load though. They have oil
filled contactors to actually break the circuits. Those are
isolators..thats just redsidual cable capaitance being broken.

I saw a detailed write-up of that (and I've got a much
better quality video of it). It's a sulphur heaxafluoride
(SF6) breaker switch, not oil. The nearest SF6 breaker
is half jammed, leaving the isolator as the only means
of breaking it. When the SF6 breaker fires, you see the
arc flash across the half of the SF6 breaker which does
open, because the other half is still jammed closed.
That starts the arc across the isolation gap.

This switch switches the line inductors in/out at the
end of a long transmission line which are correcting
for the line capacitance. It's not actually carrying
the line current.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]