I haven't any doubt you have experience. The problem was clear described
and the potential solutions where also named.
But the request was unusual.

Unfortunately I don't know too much about the american power
distribution system (except that is weird and aparently without any
rule).
What I know,  the number one technology in the Europe in switching on
20KV is a russian vacuum patented system bought by many european high
voltage breaker producers (in fact by almost all).

See here: http://www.tavrida.com/page.php?id=products
and take a look "low voltage vacuum contactor"
Buy one and take a look :)
it's a 4KA breaker with 50mS turn on and 80mS turn off.

greetings,
Vasile


On 2/2/07, Mark Peterson <mpeterson@cannontech.com> wrote:
> Responses to comments/questions:
>
> I do understand what the client is demanding.  The client is the U.S.
> Navy and they are very clear.  I'm with you that there are other ways to
> do this, and other people and I have proposed and recommended other
> means, but this is what they want.
>
> I agree that this is different than the normal meaning and application
> of shunt trip; tripping a breaker with a control signal.  I had many
> years of experience in that world designing relaying protection schemes
> for 12.5kV through 345kV systems.  Do know that not all breakers have
> shunt trip capability.  The 2000 Amp breaker in this case is exclusively
> load current/magnetically actuated.  It is very similar in function to
> the main breaker in your house panel.
>
> Forcing a remote breaker to trip by the application of a forced fault is
> nothing new and has been done in the utility industry for decades.  It
> is an implementation of a transfer-trip scheme.  The method is crude but
> very simple and effective.  The preferred method of doing this utilizes
> piloted relaying schemes that communicate the desired tripping or
> blocking action via power line carrier, radio, fiber, or leased phone
> lines.  The shunt trip method is not implemented using a big
> screwdriver, but rather appropriately designed and sized switches.
> Stuff in the utility world is designed to normally handle hundreds of
> thousands of volts at tens of thousands of amps, and to do so safely.  I
> knowingly stood 30 feet from one as it was switched across a live 34.5kV
> line with several thousand amps of available fault current that resulted
> in the remotely located 10kA breaker opening, and it was actually rather
> uneventful.  There were no flames or large arcs at all, as would be the
> case if an attempt was made to use the same switch to open the circuit,
> which is a very different situation.  There would be a ball of fire in
> that case and I have witnessed that situation.
>
> A couple things that lessen the requirements of the contactor is that
> the 3000 amp load only needs to be carried for approximately 10 cycles,
> which is the maximum time it will take for the upstream breaker to open.
> So the contactor needs to handle a momentary 3000A current rather than a
> continuous 3000A load current.  The other thing is that it does not need
> to interrupt that high current since that will be done by the breaker.
>
> FYI, there are SCRs available that can handle currents of this
> magnitude.  Semikron SKT 1600/16E devices are rated 1600 volts at 2500
> amps.  For a 150 ms pulse, they can handle 10,000 amps.  They run about
> a grand apiece, which would be acceptable for this project.
>
> Good discussion, folks.  Great minds here, for sure.
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