Whole house "battery" wiring/power...

[Jules]

Interesting - not seen those before. 'ours' were WWII-vintage, and there was compressed air in the same room as part of the air-start system for the generators, so I suppose it was no big deal to route it to the electrical switchboard too.

:-) I'm sure there were all sorts of ways and means of extinguishing arcs, though - some of which may have worked better than others!

It'd be interesting to know what larger power stations etc. did, too. Had some friends in NZ with a smaller plant (2,500 kVA) but I've not talked to them in quite a while, and I don't recall anything obviously resembling breakers on the site, although I assume they were there somewhere!

cheers

Jules

[Don Kelly]

High voltage air blast breakers for AC have been around since the late 40's. They were/are modular with series sections and could then be extended to higher voltage by adding sections. The contact opening in a section was about 1 inch and 600psi air was driven through the arc, extending it towards a vent but not actually interrupting the arc until the arc naturally collapsed at current zero- then the arc products were blown out and the gap filled with good dielectric (high pressure air). A two gap section was good for 72KV and 2 of these in series for 161KV. Two gap sections could be linked together and put on longer columns at higher voltages there was a loud bang when they operated. The advantage of these breakers from Europe was that they were smaller, lighter, faster and cheaper than the oil breakers in use up to that time in North America. There was a bit of a war of words going on in IEEE PAS regarding the relative merits of bulk oil breakers and air blast breakers and air breakers won out. Even the old circuit breakers at, say 15KV up whether oil or air blast operated on the principle of removing arc products, replacing them with good dielectric, when the current went through zero. This principle is used for HV minimum oil and SF6 breakers (blast of oil or SF6 through the gap).

------------ At lower AC voltages- say 5-15KV such breakers are often used- You could take one of these and derate it to about 400-500VDC and it would likely work. That current zero every half cycle makes a big difference.

Me too

[Archimedes' Lever]

We need big, engine block sized solid state switches. :-)

[daestrom]

Another variant that I worked with was spring to open and the bottom side of the mechanism pushed a plunger in a cylinder to make a 'gush' of air that was directed from below the contacts, up between them into the arc chute. Of course it was just a short burst of air, but the idea was to blow the hot gases up into the chute where the plates would separate and cool them.

daestrom