Why only "even" number of Generating Units in Power Station?
Why only "even" number of Generating Units in Power Station?
(OP)
So far, I have seen mostly odd number of Units in Hydro Power stations. Why does the designer choose only "even" number of units?? What is the disadvantage of having "odd" number of units??
I would appreciate some answers.
Thanks
I would appreciate some answers.
Thanks






RE: Why only "even" number of Generating Units in Power Station?
You then say that you see mostly odd numbers, followed by an assumption that designers chose even numbers.
Not easy to understand what you actually mean. But interesting question.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
Bill
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"Why not the best?"
Jimmy Carter
RE: Why only "even" number of Generating Units in Power Station?
I remember now that there was a little creek over here where eleven little hydro stations delivered just under 1 MW. They have now been replaced with one unit. So, I think that odd numbers actually are better than even numbers. And prime numbers like 11 and 1 seem to be very good.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Why only "even" number of Generating Units in Power Station?
Can we safely say that "Odd" numbers feel better? Have I missed the point again. Should I have said that prime numbers feel better. Except 13, Don't use 13 sets on Fridays.
Bill
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"Why not the best?"
Jimmy Carter
RE: Why only "even" number of Generating Units in Power Station?
Many plants use two-on-one designs with two CTG's supplying steam to one STG, so each block has three generators each of about the same size. Then you get odd numbers.
Odd or even may make a difference. If we are worried about it, should we count the blackstart and emergency generators too?
RE: Why only "even" number of Generating Units in Power Station?
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RE: Why only "even" number of Generating Units in Power Station?
First employer's power stations had:
Hydro: 3 units, 4 units, 4 units, 4 units, 5 units, 5 units, 3 units, 8 units, 3 units; Combined cycle: 4 units; Geothermal: 5 units, 5 units, 3 or 5 units (I forget), 1 unit; and some other very small methane-powered sites that I've forgotten, but they were about 4-5 units each.
Second employer:
Hydro: 2 units, 5 units, 2 units
Current employer:
Hydro: 3 units, 3 units, 1 unit, 2 units, 2 units
Diesel: 7 units, 4 units, 4 units,
So I see no real pattern in terms of number of generators at the places that I've worked at.
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
first engineer designs with even number because the plans look more symmetrical and therefore 'feel better'.
At some future time, someone figures out that they can 'squeeze' in a bit more capacity and adds one more: odd final number
Besides, it's better feng shui.
RE: Why only "even" number of Generating Units in Power Station?
http://
You can scan the list and see the number of onezies, twozies, and threezies.
I haven't done any statistical analysis on those numbers (and don't intend to!), but I don't see any pattern.
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
The nuke site I work on has two plants, with four units each. Each unit is rated at about 900MW. There is a lot of consideration given to building a new plant on site. I know that if they do it will be only two units, with each unit rated about 1600 MW. Why? Because they can build this now. When the first two plants were built it was too expensive.
The only thing you will not ever see (unless its a very small installation) is a plant with one unit. Can it be done? Yes. But what about outage situations? You lose all of your revenue for any outage.
RE: Why only "even" number of Generating Units in Power Station?
What about Grand Gulf, Port Gibson, Miss, Nuclear, 1300 MW? (although in all fairness, it was to have been 2 units, the second was sold for scrap instead of constructed.)
What about SWEPCO Gentry, Ar? One unit, ~550 MW. (although in fairness, it was to have been a 2 unit station, but the utility got fed up with the state regulators and moved the second unit to become unit 3 at their Welsh Station.)
What about Swepco Pirkey plant, lignite 8-900 MW, Lignite?
What about Cleco Dolet HIlls, lignite, 8-900 MW, Lignite, both one unit stations.
What about MP&L Natchez (now retired) one unit, ~60 MW - large station in the day it was built.
What about Oklaunion near Vernon, TX? (I can't remember if it is West Texas Utilities or who.) One unit in the 900 MW range.
I think if I kept thinking, I could come up with many more single unit stations of significant size. So, Marks, I don't think your last statement is accurate.
rmw
rmw
RE: Why only "even" number of Generating Units in Power Station?
Muthu
www.edison.co.in
RE: Why only "even" number of Generating Units in Power Station?
Looking through mgtrp's star studded post, it seems that although not all the stations that he lists have an odd number of sets, the ones that do have odd numbers all have prime numbers.
Seriously, it must be a slow day, Muthu.
Next question: Why are some plants 50 Hz and others are 60 Hz??
Bill
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"Why not the best?"
Jimmy Carter
RE: Why only "even" number of Generating Units in Power Station?
Why are some machines dc and others ac ?
(Do I get a lps for that ?)
Muthu
www.edison.co.in
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
As for AC versus DC, I guess that it depends on your personality. DC is steady and dependable but most designers seem to want more excitement and go for the peaks and valleys of AC.
(I'm starting to enjoy the new medication.)
Bill
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"Why not the best?"
Jimmy Carter
RE: Why only "even" number of Generating Units in Power Station?
Enquiring minds want to know!!
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Why only "even" number of Generating Units in Power Station?
It boggles the mind.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Why only "even" number of Generating Units in Power Station?
It was an odd assortment of colors, and somewhat feminine, I thought, soft pastels except for the deep blue condenser, but that is what she picked, and what we painted them.
Now, when it comes to E-W vs N-S, I have observed unscientifically over a long period of time that N-S oriented solid fuel boilers with wear particles in the flue gasses have heavier wear weighted to the west side of the parts of the units subject to wear where E-W oriented units have essentially even wear. Coriolis effect???? Make up your own mind. A very small percentage of a lot of particles thrown to the Coriolis reaction side of the gas passes could add up.
http://en.wikipedia.org/wiki/Coriolis_effect
I can't say whether or not that is the case, but I do know that if I ever had to site my own unit, I know which direction it would face.
rmw
RE: Why only "even" number of Generating Units in Power Station?
2 hands, 2 feet, 2 eyes
male occurs with female = gettting even
negative occurs with positive = 2 or 0, all is well whichever way you take it
Guess the universe is in harmony only when everything works out even
see, good and evil = 0, in nothingness is calm!
RE: Why only "even" number of Generating Units in Power Station?
Flexibility requirement is and always will be the main criterion for any plant designer. As posted by others, the "what if" one unit conks out?, demand rises above the capacity of one unit?, etc. . will have to be answered by the decision-makers!
Having said that, it's not only the number of units that comes into the equation but also the size of each unit, the expected demand at different times of the day, as well as the seasonal demand profile of the load served. Still, the bottom line will be how deep the pockets of the proponents have.
Respectfully.
RE: Why only "even" number of Generating Units in Power Station?
I got my answers. And I am glad my Q provided some amusement to you all.
RE: Why only "even" number of Generating Units in Power Station?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Why only "even" number of Generating Units in Power Station?
how about a tongue, a forehead, a nose, a brain. Last time I checked I only had one of each! :)
RE: Why only "even" number of Generating Units in Power Station?
RE: Why only "even" number of Generating Units in Power Station?
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