Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ub!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Are switches supposed to spark?
Summary: BIG arcs...
Message-ID: <3964@kitty.UUCP>
Date: 22 Aug 90 20:41:17 GMT
References: <27155@pasteur.Berkeley.EDU> <1990Aug22.171934.24558@zoo.toronto.edu>
Organization: Recognition Research Corp., Clarence, NY
Lines: 20

In article <1990Aug22.171934.24558@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes:
> >Are switches supposed to spark when you switch them? ...
> 
> It's pretty much inevitable when they are carrying noticeable currents.
> (Breaking the arc is the dominant design problem of really big circuit
> breakers, in fact -- when you try to cut off a circuit carrying, say,
> 1000 A at 50 kV, you get some impressive sparks! :-))

	Outdoor high voltage switches usually contain a "horn gap" which
spreads as the switch is opened, thereby specifically directing the arc
away from the actual current-carrying switch contacts.

	Other types of high voltage switches (non-oil filled type), such
as those contained in metal clad switchgear, sometimes use a source of
compressed air to blow out the arc at the time the switch is opened.
The compressed air valve is triggered by the switch controller.

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
VOICE: 716/688-1231   {boulder, rutgers, watmath}!ub!kitty!larry
FAX:   716/741-9635                  {utzoo, uunet}!/      \aerion!larry