Re: Z-Machine Sparkage - Substation Fault

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "marc metlicka by way of Terry Fritz <teslalist-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>



Tesla list wrote:
 >
 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<jimlux-at-earthlink-dot-net>
 >
 > Expulsion fuses use the disintegration of the inside of the fuse (or a
 > material specifically put in the fuse) to blow the arc out the end. The high
 > gas velocity through the orifice helps quench the arc. Who needs feeble
 > explosives when you have Megajoules of fault energy to work with.
 >
 > A few sketchy details on my page at
 > http://home.earthlink-dot-net/~jimlux/hv/fuses.htm
 >

  Jim, All
  I've worked with several different styles of expulsion fuse and one
quenching style in HV-HI ranges, the first two are on large
transformers, the last on two large drive bridges
One style, 12-30kv -at- 1-5 KA range, Uses a wire filament rod, that looks
like it was crimped along its length, runs down the center of a high
strength fiber tube. this unit threads onto the blast arrestor on the
end and looks like a "BIG" car fuse, when the fuse blows the segments,
each about .5" long, are blown by hot gas energy into the arrestor. This
is full of layers of screen that trap any pieces that are left, And cool
the gas down considerably.

  The next tube type, 15-50kv -at- 2-6 KA, Is basically the same rod type
element, But the rod is a soft metal and the arrestor is factory
attached and has a very fine, very dense screening that cools the gas
from the totally consumed rod (this one throws a very eerie blue white
cloud out the arrestor that will scare the dead. Both sound like 20_12
gauge shotguns going off at once! Each were reloaded using a strong
spring on one end of the element and stressed into position.

  The last and newer type is the ceramic type, 5-100+kv -at- 5-?? KA (ours
were 30kv -at- 10 KA. This one uses a square case of very hard ceramic the
size of a brick but hollow, the ceramic is almost .5" thick all around
with no sharp corners in or out. Inside there is some sort of "sand"?
like a white silica sand? It took me some time of dissecting to actually
see the element of the fuse, This turned out to be MANY thinner wires
running from the top tap to the bottom tap. When they blew the sand
actually melted into a geode kinda thing, melting the sand into glass
and contained inside the shell.
Since there was six per scr bridge and three bridges (a,b,and c phases),
x two 15,000hp motor drives, 36 fuses in all, these would literally
implode on your chest when over current if you were unlucky enough to be
inside the drive room at the time When these blew (I hated that!).
I type this just to show, As Jim did, How nasty even the proper
protection can be as safety goes.
  Always count on the worst and try to prepare for that, then pray.

  Take care all,
Marc M.