power and tiebreakers

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In a power plant, tie breakers are commonly supplied. Normally the tie breaker is open. If the normal feed to a bus trips or is otherwise unavailable the tie breaker can be closed to connect the unpowered bus to a companion bus that does have power available from its own normal source. In some instances the tie breaker will close automatically unless there has been a fault on the dead bus itself. Care must be taken not to overload the source that is supplying two buses when the tie breaker is closed.

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.

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

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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

l the electricians members of the

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

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!

Mexico? I would have expected worn out disk brake drums, with pieces of rope to pull them out..

Good for you. I heard that most of the emergency equipment at Homestead Air Force Base was damaged during the storms. I have a friend who ran Dad County's radio shop before Andrew. He retired and moved to north central Florida as soon as the roads were clear.

That sounds like me, when engineering refused to sign off on an ECO. :)

It would have been fun to watch, as they were hauled away in handcuffs in the back of a military vehicle to the nearest military holding cell. I don't know if anything was available at Homestead. They would have probably sent them to Eglin Air Force Base in the Florida the panhandle. Hopefully they could have found a case of Korean war surplus rations and canned water to make sure they never wanted to go back.

That doesn't surprise me, either. Progress energy had a crew on my street today to inspect power poles for damage from the hurricanes a couple years ago.

From what I hear, if you don't speak spanish, you don't want ot get near Dade county. :(

I rode out the last one in an emergency shelter for the disabled at a high school near my home. Talk about poor planning. A lot of people were diabetic, and most of those were on insulin, but they didn't think to provide refrigeration. When we located a small refrigerator in a teacher's break room, school board employees promptly arrived to remove it, putting a lot of people's lives in danger.

Not really. I was involved in the repairs to a (supposedly) redundant power system in a companies critical data center. Someone had installed some bolts in panelboard buses incorrectly and they were in danger of overheating.

It turned out that these bolts (and the associated panelboards) were single point failure locations that could take the entire data center down. Nobody could figure out how to de-energize even one source and panel at a time to perform the repairs. The whole data center had to be shut down for several days.

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.

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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...