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Posted by Steve B. on May 18, 2008, 10:44 am
>
>What are these things for? What do they do?
>
Here's an answer from our family electrical inspector...
Steve B.
"Oil circuit breakers and/or re-closures…
95% of things in series (on power lines) are some type of switch.
Often you will see they also have a fuse in parallel to them (but
open)..the fuse is in series with the power line also.. the fuse is
there, to be manually closed, in the event the C/B goes bad or needs
servicing.
Because of the voltage, if the breaker needed to open, especially
under "fault" (short) the amperage it needs to break might be
thousands of amps, therefore , the operation is all contained in a
canister filled with non-conductive oil. The contacts opening in oil,
without air, prevents flash & damage to the C/B.
They could be re-closures or a combo beaker/re-closure. Re-closures
are critters that, as their name says, reclose the line. They are set
for a certain amount of times (usually 3) so if something happens like
a squirrel gets on the transformer, the squirrel shorts, the breakers
opens, light go out.. the "blast" at the transformer ends with the
squirrel flying, clearing the "fault". The re-closure, in a preset
time, closes the line back minimizing the outage.
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Posted by Nate Nagel on May 18, 2008, 11:58 am
Steve B. wrote:
>>What are these things for? What do they do?
>>
>
>
> Here's an answer from our family electrical inspector...
>
> Steve B.
>
>
> "Oil circuit breakers and/or re-closures…
>
> 95% of things in series (on power lines) are some type of switch.
> Often you will see they also have a fuse in parallel to them (but
> open)..the fuse is in series with the power line also.. the fuse is
> there, to be manually closed, in the event the C/B goes bad or needs
> servicing.
>
> Because of the voltage, if the breaker needed to open, especially
> under "fault" (short) the amperage it needs to break might be
> thousands of amps, therefore , the operation is all contained in a
> canister filled with non-conductive oil. The contacts opening in oil,
> without air, prevents flash & damage to the C/B.
>
> They could be re-closures or a combo beaker/re-closure. Re-closures
> are critters that, as their name says, reclose the line. They are set
> for a certain amount of times (usually 3) so if something happens like
> a squirrel gets on the transformer, the squirrel shorts, the breakers
> opens, light go out.. the "blast" at the transformer ends with the
> squirrel flying, clearing the "fault". The re-closure, in a preset
> time, closes the line back minimizing the outage.
That makes more sense than a transformer to compensate for voltage drop;
one would think that that would require a ground/neutral connection.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
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Posted by Pete C. on May 18, 2008, 4:26 pm
Nate Nagel wrote:
>
> Steve B. wrote:
> >>What are these things for? What do they do?
> >>
> >
> >
> > Here's an answer from our family electrical inspector...
> >
> > Steve B.
> >
> >
> > "Oil circuit breakers and/or re-closures…
> >
> > 95% of things in series (on power lines) are some type of switch.
> > Often you will see they also have a fuse in parallel to them (but
> > open)..the fuse is in series with the power line also.. the fuse is
> > there, to be manually closed, in the event the C/B goes bad or needs
> > servicing.
> >
> > Because of the voltage, if the breaker needed to open, especially
> > under "fault" (short) the amperage it needs to break might be
> > thousands of amps, therefore , the operation is all contained in a
> > canister filled with non-conductive oil. The contacts opening in oil,
> > without air, prevents flash & damage to the C/B.
> >
> > They could be re-closures or a combo beaker/re-closure. Re-closures
> > are critters that, as their name says, reclose the line. They are set
> > for a certain amount of times (usually 3) so if something happens like
> > a squirrel gets on the transformer, the squirrel shorts, the breakers
> > opens, light go out.. the "blast" at the transformer ends with the
> > squirrel flying, clearing the "fault". The re-closure, in a preset
> > time, closes the line back minimizing the outage.
>
> That makes more sense than a transformer to compensate for voltage drop;
> one would think that that would require a ground/neutral connection.
>
> nate
>
> --
> replace "roosters" with "cox" to reply.
> http://members.cox.net/njnagel
You can tell the regulators pretty easily, they are typically fairly
large and they nearly always have a decent size dial gauge mounted at
the top angled down which indicated the transformer tap is currently
selected. They normally also have a conduit down the pole to a small
control box.
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Posted by bud-- on May 18, 2008, 12:13 pm
Steve B. wrote:
>> What are these things for? What do they do?
>>
>
> Here's an answer from our family electrical inspector...
>
> Steve B.
>
>
> "Oil circuit breakers and/or re-closures…
>
> 95% of things in series (on power lines) are some type of switch.
> Often you will see they also have a fuse in parallel to them (but
> open)..the fuse is in series with the power line also.. the fuse is
> there, to be manually closed, in the event the C/B goes bad or needs
> servicing.
>
> Because of the voltage, if the breaker needed to open, especially
> under "fault" (short) the amperage it needs to break might be
> thousands of amps, therefore , the operation is all contained in a
> canister filled with non-conductive oil. The contacts opening in oil,
> without air, prevents flash & damage to the C/B.
>
> They could be re-closures or a combo beaker/re-closure. Re-closures
> are critters that, as their name says, reclose the line. They are set
> for a certain amount of times (usually 3) so if something happens like
> a squirrel gets on the transformer, the squirrel shorts, the breakers
> opens, light go out.. the "blast" at the transformer ends with the
> squirrel flying, clearing the "fault". The re-closure, in a preset
> time, closes the line back minimizing the outage.
A little longer answer:
Imagine rural distribution starts from a point with distribution wires
going out like a tree. If you have a fault at some point you want
minimal disruption of the distribution. Everything downstream from the
fault would be disconnected and everything else would be on.
You could put fuses at 1 mile, 2 miles, ... from the feed point to
isolate the fault. The problems is that a fault at 5 miles is likely to
blow the fuses at 4 miles, 3 miles, 2 miles, 1 mile. The outage is not
minimized.
A method commonly used is to put "sectionalizers" at 1 mile, 2 miles, 3
miles. At the source is a "recloser". On a fault, the recloser opens.
If there was fault current at the 3 mile sectionalizer, the fault is
beyond that sectionalizer and when the recloser opens that sectionalizer
will open.
The recloser then closes. If there is still a fault the recloser opens
again. If there was fault current at the 2 mile sectionalizer it will
open. The recloser connects again....
Sectionalizers 'count' the reclosures and open depending on how they
have been set, which depends on how many sectionalizers there are to the
recloser. After the closest sectionalizer would have opened, if there is
still fault current the recloser stays open. The result is only the
minimum required part of the system is killed.
Sectionalizers always open when the circuit is dead so they don't have
to open on fault currents. That means they can be pretty small. That is
probably what you saw.
Reclosers do open on fault current - multiple times. They have to be
quite large, more like a refrigerator or larger.
You need a sectionalizer (and recloser) in each hot wire. With 3 phases
on the pole you need 3.
--
bud--
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Posted by on May 19, 2008, 4:03 pm
On May 19, 3:48=A0pm, letter...@invalid.com wrote:
>=A0At the same time, these devices also have a fuse right
> next to it. =A0That still leaves the question why the fuse itself is not
> enough protection ????
As was mentioned earlier, the fuse is there to bypass these devices in
case the device needs to be serviced.
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