Load Calculation Backup Generator

Me wrote:


As long as any idiot can just buy a genny over the counter, then there are going to be backfeeds. When it comes to "how often anyone suspects", in my case I suspect that it is pretty common.
That's why I did find it a little suprising that linemen have been injured/killed by such backfeeding, unless they weren't following SOP. I could just about imagine it happening with lv lines, eg the line from local transformer to the house. But I couldn't imagine an engineer working with an hv line taking short cuts. You don't get a second chance with 11kV, or whatever equivalent voltage you use.
It is not just toy gensets that are available - my local toolhire shop will quite happily let anyone hire a 20kVA baby and tow it home...
http://www.hss.com/g/41520/Generator_20kva_Silenced__Bt.html
--
Sue










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Palindr☻me wrote:

When the crew is working 16-hour days for multiple days, I suspect that SOP is occasionally not followed, either as intentionalal short cut or more likely, just from being tired.
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Was that before or after you astronaut programme employment?

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In HV (V>f kV in Europe) they use grounding switches, besides opening breaker and disconnect switches, that connect each leg to the ground not only of accidental breaker closing but also induced voltage of parallel lines.I have also seen a voltage tester for MV when some linemen did something in MV in my neighborhood.Normally in MV (V> kV<%kV)you have to test and then connect together all phases and to ground, I don't know how exactly they do it.But in Kozani (where the brown coal is, 70% of Greece's electricity is generated there)terrible accidents have happened.Some poor lad opened the 20 kV bus bars cabinet and all they found of him was his shoes.Some other touched an energized 150 kV wire and he was zapped like a mosquitoe.
-- Tzortzakakis Dimitrios major in electrical engineering,freelance electrician 542nd mechanized infantry batallion dimtzort AT otenet DOT gr
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There are always idiot linesmen out there as well as idiot generator installers.
Yes, they have a protocol that insures safe handling but many are not the sharpest knives in the drawer either and using the procedures can take away from their macho manhood sometimes.
wrote:

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What if the "some idiot" was one of these green types that has their own wind farm/solar panel setup that back-feeds spare power back into the grid?
It's always puzzled me what happens when you've got one person in a street with that kind of setup, and there's a cable break ... one person tries to power the whole street ... linesman gets zapped from the "dead" side of circuit etc ... mmm ... messy!
--
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Mike Brown: mjb[at]pootle.demon.co.uk | http://www.pootle.demon.co.uk /
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Mike wrote:

Not if it's designed properly. The small amount ow power available won't "power the whole street" and it will disconnect from the line. Do you think a utility would allow them to be set up to sell power without the proper safeguards?
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
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I did say "tries to ..."

I would hope not. However, we're back to the person with the generator with 13A plug (live) fitted on the end ... you would hope the utility wouldn't allow that either, but people do retrofit stupid things onto existing good systems, and they can go undetected for quite a while!
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Mike Brown: mjb[at]pootle.demon.co.uk | http://www.pootle.demon.co.uk /
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Mike wrote:

All of the controllers designed to do this synchronize the output to the frequency of the grid. If synchronization is lost the controllers output ceases in less than one cycle.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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Pasted from Wikipedia: http://en.wikipedia.org/wiki/Electric_chair
In order to prove that AC electricity was dangerous and therefore better for executions, Brown and Edison, who promoted DC electricity, publicly killed many animals with AC, including a circus elephant. They held executions of animals for the press in order to ensure that AC current was associated with electrocution. It was at these events that the term "electrocution" was coined. Edison introduced the verb "to westinghouse" for denoting the art of executing persons with AC current. Most of their experiments were conducted at Edison's West Orange, New Jersey, laboratory in 1888.
and from: http://en.wikipedia.org/wiki/Thomas_Edison
George Westinghouse and Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over the more easily transmitted alternating current (AC) system developed by Nikola Tesla and sold by Westinghouse. Unlike DC, AC could be stepped up to very high voltages with inexpensive transformers, sent over thinner wires, and stepped down again at the destination for distribution to users. Despite Edison's contempt for capital punishment, the war against AC led Edison to become involved in the development and promotion of the electric chair as a demonstration of AC's greater lethal potential versus the "safer" DC. Edison went on to carry out a brief but intense campaign to ban the use of AC or limit the allowable voltage for safety purposes. As part of this campaign, Edison publicly electrocuted dogs, cats, and in one case, an elephant[3] to demonstrate the dangers of AC. Widespread use of DC ultimately lost favor, however, continuing primarily in long-distance high-voltage direct current (HVDC) transmission systems.
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That's a good plan, that'll set my mind at rest for now :)
Mike.
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Suspect what you wish. Whether a dirty, sweaty lineman gets hit by 120v ac or 1200v, under many circumstances she or he'll be just as dead.
So this is not an abstract game.
J
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Zero facts in those references:
I didn't mean to infer that backfeed isn't an issue, I was only pointing out the nonsense about blowing up transformers, etc.
You also removed the last line in my post where I clearly stated that a transfer switch was called for.
I stand by my statement that if the whole grid is down, an 8 KW generator isn't going to energize it or blow anything up.
This reference says about the same thing:
http://www.lineman.com/about_articles4.cfm
"...The hazard of generator back feed seems to be greatest when lineworkers are working on a single transformer or a small section of line. "Portable generators and motors are usually not powerful enough to supply large utility loads, and the voltage will tend to collapse under those circumstances," explains Drew...."
They go on to say the obvious, "Always consider the possibility of back feed when working on de-energized lines, and consider from which direction the power could flow. "This should be discussed during each job briefing session," Drew emphasizes...."
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On Tue, 09 May 2006 16:31:43 -0700, jaywitkow wrote:

...
...
So, what you need to do is "load balance": inspect the house wiring, and find out just what the load actually is on each leg. (with USA 240VCT, they're not phases, they're legs, since there is nothing to shift the phase, it's only a center-tapped 240V).
If the house was wired by competent people, most of this should already have been taken care of, since the power company likes balanced loads too.
If you need to run the toaster oven and space heater simultaneously, for example, plug one into leg "A" (black/white) and the other into leg "B" (red/white). These can even both be on a duplex outlet, if you break the shorting tab.
Or, you could go full-goose bozo, and buy all 240V appliances. ;-)
And, just FYI, the power company should be very helpful with the crossover switch issue.
Have Fun! Rich
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Rich Grise wrote:

. . .

Well, I have done a lot of work on this since my original post. First of all, I did an audit of all the breakers and found out where they go and what leg they are on. With a little research, I found that with the older, larger-sized breakers, the legs alternate with every breaker. With the new, smaller-sized breakers, they also alternate, but there are two breakers in a single package that is the size of one of the old breakers.
After assigning the leg number to each breaker, I spot checked my results with a volt-meter by checking a number of outlets. If you get a 240V reading, then obviously, the meter is connected to opposite legs.
Then I also did some math for load management. It turns out that I am very lucky. The load balancing is very good just like it is. I was prepared, though, to rewire some of the breakers if I had to. This wouldn't be very difficult.
Then I got lucky again and found a used Briggs & Stratton, Wheelhouse 5,550W at a local pawn shop for $389.95. It looks new and runs perfect and I checked the voltages with a test load (electric heater). This saved me about $800-$900 because I was going to buy a new 8000W generator.
Now I have a new problem. This thing is very noisy! The first thing I'm going to try is installing an automobile muffler on it. Unfortunately, though, the flange and pipe and muffler are all one piece and I don't want to destroy the muffler by cutting the pipe. However, it looks like I got lucky again. I found a seller on ebay that is selling Briggs & Stratton flanges that will fit my engine. So, I'm going to give the automobile muffler option a try.
If that doesn't work, there's a website that shows a method of enclosing this kind of generator in multiple boxes. If I have to, I guess I'll do that. That website, by the way, is at: http://soundproofing.org/infopages/generator.htm
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Good job!

Yep, I think we told you about that.

Be sure to have a flexible connection connection between the muffler and the flange. Otherwise you will break the flange or the bolts that connect it to the engine. Of course, the muffler can only reduce the exhaust note; there is other noise...

Someone mentioned sandbags. Those coupled with (perhaps) a hedge sounds like a useable idea. Or perhaps concrete blocks stacked and filled with sand? I use Home Depot wooden fence. I nailed an extra layer of wooden pickets on it to make it double thick, and sealed it at the bottom so the noise can only escape at a high angle. Whatever you do, don't forget that cooling air must somehow get in and exhaust & hot air must somehow get out.
Vaughn

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Vaughn Simon wrote:

Sandbags?! That's an interesting idea. In doing some searching on Google, it looks like the drawback is that they rot with time. Dayton Bag & Burlap (http://daybag.com/industrial/sand_bags.html ) has some special "CIA 12BB" bags that last "up to 3-5 years". My guess is that if I put a roof over them, they could last a lot longer than that.
Coincidentally, I have a rather large, 25-year-old sandpile that I would like to remove and cleanup. So, I could kill two birds with one stone.
I could, perhaps, build a small roof that would lay on top of the bags. Maybe I could make it out of heavy particle board and roll roofing. That would look better than simply throwing a sheet of plastic over the "bunker" to protect the bags from the sun. That might also provide some additional sound proofing. If I did that, I would still have the problem of sound proofing the open entrance that I would need to wheel the generator in and out of, though.
Nothing comes to mind at the moment for the entrance. So, I'll have to do some thinking about that. I suppose I could make an L-shaped entrance so that the sound would have to go around a corner to get out . . ."
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On Sat, 13 May 2006 08:34:00 -0700, jaywitkow wrote:

Aren't they made of plastic these days? If a poly or nylon or kevlar bag rots in only a few years, why are they all worried about it filling up the landfills?

Well, there is that. :-)

THat's easy - point it away from the house. :-)

Just line the room with some cheap shag carpet remnants - maybe drive around and look for someone who's having their carpet replaced. Put up a chimney for the exhaust; that'll get the noise farther away, plus keep the exhaust fumes out of the intake, and out of the generator room! :-)
Have Fun! Rich
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Rich Grise wrote: ...

Rot isn't exactly the right word. Ultraviolet light will cause most plastics to decompose over time. It's exposure to sunlight that is the problem.
Anthony
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wow, i spawned alot of talk with my lineman electrocution post. :P
And about the transformer explosions... I really diddnt mean "explode" but if you try to run an old pole transformer backward after it's been running one direction for 10+ years, it may not like it and may fry some windings on it. But hey who cares, that's the power company's problem :)
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