power and tiebreakers

[David Williams]

Hello,
Can anyone give me information on the purpose of a tiebreaker
that is found in switchgear power distribution?
This is more of an electrical than electronic question but
I could not find an electricicity newsgroup.

Meaning, in a typical building, you have power that comes
from the street and goes into switchgear, then a transformer, then
a feeder panel that has a tiebreaker switch there.

As I understand it, if you have two feeders into a system,
and one feeder fails, the tiebreaker switch opens up so that
bad/faulty electricity from the bad feed cannot flow through the sysem
until it is safe. That is about all I know.

Anybody have any resources I can read on this?

Thanks,

David

 

[JeffM]

This is more of an electrical than electronic question but
I could not find an electricicity newsgroup.

The majority of Usenet is archived and is quite searchable.

Can anyone give me information on the purpose of a tiebreaker
that is found in switchgear power distribution?

http://groups.google.com/groups/search?q=switchgear+electrical+-jobs

 

[mpm]

A tie breaker (bus tie breaker) or switch is used to connect busses
together that are normally fed from independent sources. This is usually
done when performing maintenance on one of the sources so it can be
taken off line and the loads on its bus may be powered through the tie
breaker.

There are also some situations in which busses may be paralleled in
normal operation (tie breaker and both feeds closed), but it is
necessary to provide a means to disconnect one of the busses from the
other in the event of a fault.

Ch-4 (TV) in Miami went off the air for about an hour once because
someone had the bright idea to tie the UPS in separate from the
generator.

Utility power goes out, runs on UPS. (20 minutes run time reserve)
Generator won't start. UPS dies.
Generator finally started (after some effort), BUT the UPS would not
release the tie until it recharged.

Long story short: Main, UPS and Generator - and there the station was
sitting in the dark.
Unbelievable.

 

[legg]

Ch-4 (TV) in Miami went off the air for about an hour once because
someone had the bright idea to tie the UPS in separate from the
generator.

Utility power goes out, runs on UPS. (20 minutes run time reserve)
Generator won't start. UPS dies.
Generator finally started (after some effort), BUT the UPS would not
release the tie until it recharged.

Long story short: Main, UPS and Generator - and there the station was
sitting in the dark.
Unbelievable.

If you've got a dead syatem, there has to be a manual procedure and
hardware present to allow manual over-ride of the dead hardware.

When a UPS is configured, it's important to determine who's on first.

RL

 

[mpm]

� �In Miami? �I believe it. �Aren't all the electricians members of the
IBEW?

Hey Mike!

I could probably come up with some smart-ass acronym for "IBEW" that
includs all the relevant racial (latin/cuban/south american) slurs,
but I'm afraid my Spanish is just too rusty...

Although perhaps no longer contained to just South Florida, when
exactly does "Immigration" become an "Invasion"? -mpm

 

[Richard Henry]

   My problem with the IBEW and Miami was all the shoddy work done on
fairly new homes that their members wired just before Hurricane Andrew.
The buiding inspectors who let them get by with the bad work were all
long gone, as well.  

A better electrical insatllation would have made the houses more
resistant to the hurricane?

 

[mpm]

On May 8, 12:02�pm, "Michael A. Terrell" <[email protected]>
wrote:

I hear you loud and clear, Michael.
But that's what you get when contractors can't read the plans because
the plans are in English.
For that matter, the permitting & zoning dept doesn't speak English
either, so I guess they have no choice but to rubber stamp whatever's
put in front of them.?

Or possibly (and this is the truly scary alternative...) that quality
of construction is actually considered a vast improvement over what
they're used to "back home".

Hell, I know an AM station in Mexico that uses modified, welded shovel
heads for their electric disconnect. (I am not kidding!!)

True story: I actually got "escorted" out of Dade Co. Permitting &
Zoning once because 6 months after the hurricane, we could not get a
simple 60-amp agricultural drop to power an emergency radio tower &
shelter we had erected in the hours following the hurricane. They
actually claimed the installation was "illegal" because we hadn't
pulled a permit for the temporary electric - and they refused to even
talk to us until that was remedied. Hello!! The department was
closed for weeks after the storm! And the backlog was so bad
afterwards, we couldn't get in, even when they did open up! We were
actually doing them (and Dade Co residents) a favor by waiting.

By that time, we had roughly 110kW of generator, and only needing
about 30, gave the rest to the military - which promptly set up a 24-
hour, armed command and control center right on the site. It's not
like we were hurting....

In fact, we were also providing antenna space on this same tower for
Miami-Dade Fire Rescue and Dade Co. Emergency Services. Free of
charge, I might add. But I digress..

Anyhoo, after the rough treatment by Dade Co., and being advised we
actually had to take the temporary tower & electric down (even though
the original tower had not yet been reconstructed), I placed just one
call.

It was to US Marshall Service (who coincidentally, were tenants on the
temporary tower seeing as it was the only one still standing!).

The very next day, they arrived at Dade Co. P&Z and informed both the
Chief Electrical Inspector and the P&Z Director that they had their
choice of going to jail right then and there, or they could issue the
temporary permit. (I guess a 3rd option would have been for Code
Enforcement to try to get past the military...?)

We had our permit that afternoon.
And for the record, I don't think they were waiving those handcuffs in
Spanish.
(Actually, I wasn't there for all this, but I heard about it.)

It still took another 2 months for FPL to get permanent power out
there!!

But now that the "invasion" is over, I'm wondering if we should have
called INS back then instead? And that was in '92. Can you
imagine how bad it must be now?

Oh, and lest I forget....
People do not realize just how bad a hurricane can be.
Cat-3 and above for sure.... Evacuate!

 

[JosephKK]

Ch-4 (TV) in Miami went off the air for about an hour once because
someone had the bright idea to tie the UPS in separate from the
generator.

Utility power goes out, runs on UPS. (20 minutes run time reserve)
Generator won't start. UPS dies.
Generator finally started (after some effort), BUT the UPS would not
release the tie until it recharged.

Long story short: Main, UPS and Generator - and there the station was
sitting in the dark.
Unbelievable.

A PE that could not be bothered to check the NEC should have been
sued. See Articles 700, 701, and 702 would be a good start.

 

[mpm]

A PE that could not be bothered to check the NEC should have been
sued.  See Articles 700, 701, and  702 would be a good start.- Hide quoted text -

- Show quoted text -

The interesting thing about radio & TV broadcasting, is that many of
the station "engineers" are not in fact P.E.'s
I suspect this particular situation was "engineered" by someone who
did not fully appreciate, or recognize the possibility that the UPS
might fail to release itself until it was re-charged. The designer
should not have relied so heavily on the UPS's disconnecting means,
and should have installed manual override controls...