I teach at a small college in a small southern city. Three years ago a peculiar thing happened. At about two in the afternoon, suddenly the lights went out and our computers, we're talking the entire building, power down to sleep mode. The green power lights are on, but the screens are dead and the machine is dormant. Flourescent bulbs flicker at about 1/10 brightness. We find out later that the local middle school had let out early because of a plumbing problem and all the kids ran home, turned on their stereos, nintendos, etc., causing a huge unexpected spike in demand and drawing down juice from the college. At least this was the explanation I heard. Sound reasonable? We were without functionable power for hours. My point is that if something this simple can have a profound, though shortlived, effect, how in the world can anyone be confident of power on Jan 1 when so many screwy variables will be likely.

-- Kurt Ayau (Ayau@iwinet.com), November 17, 1999

Answers

Oh......I thought you said Electric Ladyland....... Still rainin', still dreamin'............

-- Jay Urban (Jayho99@aol.com), November 17, 1999.

Kurt,

That explanation (the kids turning on their home equipment) does not seem plausible, unless some of those kids have aluminum smelting plants, or some comparable electrical loads, at home.

Jerry

-- Jerry B (skeptic76@erols.com), November 17, 1999.

Because the pollies believe that the electric companies don't use computers to generate and distribute electricity and even if they do, there are no dates involved. They would have to believe this in order for y2k to be a non-event, causing no disruption to the electrical grid (and pretty much everything else on the face of the earth to boot). But you see we have a problem, because the Senate reports say the opposite. They tell us that y2k is pervasive on all levels of generating and distributing electricity.

-- Larry (cobol.programmer@usa.net), November 17, 1999.

Well, technically, only nuclear physics classifies the properties of "strange, "charm", "spin", "charge", "Up/down". .....

But, I guess y2k topics invlove all those too...

You're exactly right, massive changes in "use" of the grid and the utilities are a concern - there is for example, a massive cycle in water pressure at the first commercial break in the Super Bowl when millions of toilets are flushed at the same time. Helping slightly (at rollover) is the fact that most industrial processes are going to off-line.

-- Robert A. Cook, PE (Marietta, GA) (cook.r@csaatl.com), November 17, 1999.

Do the math! How many kids could it have been? How many watts of power did/does the average middle school kid type entertainment device use? Now, having that result in-hand, what percentage of early afternoon town usage does it represent? Lastly, do you think that your power supplier can tune their system to that fine a degree?

To me, it sounds like a likely case of CYA with a very convenient excuse.

IMHO. nothing is impossible, but some things are just not very likely.

-- Ninh Hoa (tech@univ.now), November 17, 1999.

Sounds like your building lost one phase. It would seem to me the kids run home when the bell rings every day, we can't blame this one on them :)

Happened to us last month, tennants reported the little green monitor lights on but the computer was down. Feedback I guess, enough to excite the little lights, don't really know.

Since the power grid connects multiple generation sources over wide ranging distances, I would like to know what kind of control system it takes to monitor and supervise the lines to keep everything in phase. (Different issue than your power outage, but remotely related.)

Tom Beckner

-- Tom Beckner (tbeckner@xout.erols.com), November 17, 1999.

Sure, it sounds believable -- as long as you're willing to believe *anything*. [g]

-- Ron Schwarz (rs@clubvb.com.delete.this), November 17, 1999.

I, for one, think it was a squirrel.

-- Mara (MaraWayne@aol.com), November 17, 1999.

Tom,

In response to a question regarding keeping thngs in phase, in the thread:

Electricity Generation and Distribution 101

Malcolm Taylor replied:

"There are no devices or methods needed to keep the generators in sych. Once sychronised and closed initially, the magnetic coupling is sufficient to maintain synch. Without going into too great an explantion of reactive power, phase angles and rotor angles, a simple explanation would be: If a generator tried to get out sych by spinning its rotor too fast or too slow, then the voltage induced in the stator (in phase with the current) would start to fall. As the power being produced hasn't changed, then the current must rise, and a higher current means a stronger magnetic field being produced in the stator. And as the rotor is just one big rotating magnet anyway, then it would rapidly be pulled back into line with the rotating magnet field in the stator. Thus it is almost impossible for a generator to get out of synch."

"It can happen though, if the turbine is producing a high amount of power, and the magnetic field in the rotor is allowed to drop to such a stage that it can no longer stay in synch, then the generator will "pole slip". Protection devices built into the excitation will first try to prevent the field from dropping so low, and if the magnetic field did fail then field failure relays would operate to trip the generator off line."

My acquaintance with the subject is not sufficient for me offer any supplementary comments.

Jerry

-- Jerry B (skeptic76@erols.com), November 17, 1999.

Key word and tricky phrase there: "....once in synch..."

It's getting the two ac machines in synch at exactly the right millisecond and then getting the inbound circuit breaker tripped (closed) precisely while they are in synch (actually, the inbound generator should be 1% faster than the on-line machine - but I'm nit-picking to avoid reverse-powering and tripping the inbound machine.....) that requires special phase measuring circuits, remote circuit breaker controls, remote speed controls on the second generator, a trained operator, and lots of practice.

But, once in synch - they will (if properly adjusted with the right speed drop, maintain themselves in synch and load-share properly.

Again, nothing a church deacon can do.

-- Robert A. Cook, PE (Marietta, GA) (cook.r@csaatl.com), November 17, 1999.

Fair Warning:

Malcolm Taylor is either a moron, a shill, or both.

I'm no expert, but in a recent in-depth conversation with this person, "it" didn't know the meaning of a "mission critical" embedded system. Kept saying a "gate controller" which could be worked around without a disruption of power generation was a "mission critical" embedded system.

Check it out for yourself.

http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=001lWd

-- GoldReal (GoldReal@aol.com), November 17, 1999.

FYI, Dick Mills seemed to give a pretty good explanation of synchronization here:

Another Myth, We Need Computers to Synchronize

-- Hoffmeister (hoff_meister@my-deja.com), November 17, 1999.

Larry: The reason that some of us believe that is because we work there. Think of it as actual working knowledge vs. Internet BS.

Robert: The story of the Super Bowl bathroom break is a long discredited urban myth. Jerry Bs comments were correct. Turning on TVs etc. isnt going to cause any significant change.

And in terms of getting the machines to the right millisecond.

Actually no. When you are synching in the system some slop is allowed. Remember this was originally, and still is when need be, done by hand. You need a synch scope of course but you can be off by a number of cycles and the machines will still lock in. Each cycle is 16 milliseconds in a 60 cycle based system. Also the closing times of breakers vary from 5 to 8 cycles. Getting it all to the millisecond is virtually impossible.

Jerry B: You are confusing being in phase with losing a phase. What Tom means is that a phase is lost (open circuit) Think of the college having at three phase supply and one phase gets dropped but the other two remain. My guess is that may have happened in Kurts case. Its called being single phased. If the phase thats lost is on the other side of a delta-Y bank its possible they would be getting three phase though the delta but at a much lower voltage. That would also explain why it lasted so long.

Being in phase means that the phases maintain their 120 degree separation and that A phase in one part of the system is the same as A phase in another part of the system.

GoldReal: Malcolm is neither a shill nor a moron. He was referring to the gates that control the flow of water in a hydro system. The spillway gates. They are critical because they control the flow of water through the turbine, hence the speed to the turbine. But you are right in one thing. You are no expert. Thats obvious after reading your post.

-- The Engineer (The Engineer@tech.com), November 17, 1999.

The Engineer,

A "Teacher" such as Malcolm Taylor presents himself to be is fair game to be critized when he makes such a moronic error as to misidentify a "non-mission critical" embedded system as a "mission critical" one, and then attempts to justify his obvious error.

It's people just like this in positions of power and influence who must be "right" at the expense of being "correct" (there IS a huge difference) that has lead to this whole Y2K debacle.

-- GoldReal (GoldReal@aol.com), November 17, 1999.

True, very true - we are talking a speed difference of 1 or 2 cycles (several hundredths of a second, not thousandths of second), with a requirement to begin shutting the breaker as the synch meter comes to the 11:00 position with it rotating positive at 3-6 rpm, so it (the actual breaker) shuts at 12:00 after the delay, blah/blah/blah.

Coming in out of phase will complete a Marine Corps synch = break things and kill people - if the generator is large enough. Merely break things for a smaller unit.

Let the EO's and RO's twist the breaker controls.....it's their job; not mine any longer.

What we are illustrating here is to show the principle(s) involved, not trying to get some deacon to bring in two generators onto the same circuit.

-- Robert A. Cook, PE (Marietta, GA) (cook.r@csaatl.com), November 17, 1999.

I forgot to mention that it was later discovered that the local chapter of the Virginia Juvenile Steel Foundry Workers fired up their smelters for the first time that afternoon, so that could be the reason. No one knew they were turning out high quality steel in the middle school basement. 8>)

Interesting answers, about 4% of which I understand. But thanks for all the email!

-- Kurt Ayau (Ayau@iwinet.com), November 17, 1999.

"The" ? Engineer,

Tom referred to losing a phase in the first two paragraphs of his post. In the third paragraph he referred to keeping keeping things in phase among multiple generation sources. It was in reference to the latter that I posted MT's comments.

GoldReal,

Your posts suggest that there is a clear, unambiguous, definition of "mission critical" with which all people who are not morons and/or shills agree. That does not seem to be the case, and insulting people will not make it so.

Jerry

-- Jerry B (skeptic76@erols.com), November 17, 1999.

Kurt,

Ah, yes, those VJSFWs! We keep forgetting about them! :-)

Jerry

-- Jerry B (skeptic76@erols.com), November 17, 1999.

Jerry B.

You are correct. Mea Culpa.

-- The Engineer. (The Enginer@tech.com), November 18, 1999.