Primary voltage
- Thread starter domnic
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jeremy.zinkofsky
Senior Member
- Location
- nj
To do what exactly? Calculate current, VA?
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
4160 volts has been a standard medium voltage rating for distribution systems for many decades. I don't often see it along city streets. But I do see it in large industrial complexes and in some university distribution systems. If that is what the utility is providing as a primary voltage, and if you want 208/120 for your building, then you need to get a transformer rated per your description.
jeremy.zinkofsky
Senior Member
- Location
- nj
Oh, I see. Didn't understand the question.
jeremy.zinkofsky
Senior Member
- Location
- nj
I believe that the standard voltages were chosen because they were determined to be the most efficient voltages for power distribution.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
The higher the voltage, the lower the current for the same amount of power.
DC is more efficient than AC.
I think like a lot of other things, voltages were just chosen because they were chosen. There does not appear to be any reason to a lot of it to me. For the most part, it probably does not make much difference. The difference between selecting 4160 V and (just as examples) either 3500 V or 4500 V, probably just does not matter.
Why did some places select 60 Hz and others 50 Hz. There are even a very few places using 25 Hz IIRC.
jeremy.zinkofsky
Senior Member
- Location
- nj
The light bulb started it all! Initially we needed electricity to power light bulbs which needed 100V. Utilities provided 110V - 120V to account for voltage drop. As our need for electricity diversified Utilities were constantly searching for ways to distribute electricity more efficiently (efficiency equals money savings). Once AC gained dominance, the search for efficiency was constrained by the arithmetic of 3-phase systems. For example, multiply 120 by the square root of 3, you get 208. 4160V came about in the same way, 3-phase power distributed at high voltage and then transformed where needed in an effort to be efficient. The standard voltages were fine tuned based on what will save the most money. I won't get into the detailed math behind transformers but to prove my point, multiply 4160 by the square root of 3... you get 7200V. Which is another standard distribution voltage. So yes, they were chosen because they were chosen but the choices were constrained by the electrical appliances we originally used.
- Location
- Illinois
- Occupation
- retired electrician
Not sure how those two fit together....4160 is a phase to phase voltage and 7200 is a phase to ground voltage from a 12470 volt 3 phase wye system.
I believe that one of the earlier systems was 2400 volts, and often single phase transformers were used connected in delta....you can reconnect those same transformers in wye and feed them with 4160.
both 7200/3 and 12470/3 ph-ph are common in mining
as was said they kept increasing voltages as technology advanced and demand increased
2400 x sqrt 3 = 4160
4160 x sqrt 3 = 7200
7200 is 12470
And so on
there are some gaps but for some reason engineers like sqrt 3 lol
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I was taught that voltages were typically combinations of winding in series or parallel and then in wye or delta
This allowed electrical systems to 'grow' quickly by simply reconfiguring motor and transformer windings to accommodate higher voltages.
In the US, the typical starting point was some factor of 240V.
This allowed electrical systems to 'grow' quickly by simply reconfiguring motor and transformer windings to accommodate higher voltages.
In the US, the typical starting point was some factor of 240V.
- Location
- Illinois
- Occupation
- retired electrician
Did not know that 7200 is a phase to phase voltage....the only places I have seen it was as phase to ground. Thanks.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Don,
http://quotefail.com/quote/thomas-jefferson-when-people-fear-government-there
Nevertheless it is a great line.
http://quotefail.com/quote/thomas-jefferson-when-people-fear-government-there
Nevertheless it is a great line.
Mining is the only place I've seen it
common in small low coal mines
in PA the law limits underground V to 15000 so 12460 is common in big mines
but with long runs and numerous x000 HP motors they could use more
in higher mines out west 25k is allowed
it's a crazy environment all cables ( no conduit)
hung against or laid on earth, water, subject to physical damage by large mobile equipment
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Its funny this came up. I just noticed the sqrt(3) pattern while looking at some MV transformers and was going to post a topic on it. My theory was basically what you said, that it started with 2400, then at some point they bumped it up to 4160Y so they could still use the 2400 stuff line to neutral for single phase or a three phase bank Y connected. Then they just kept going and there was always the advantage of keeping with the sqrt(3) factor so they could use transformers on several systems and lower inventory. Just my conjecture, but it must be at least somewhat along the lines of how it progressed.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Here is a paper I stumbled across where the first few pages discuss the evolution of distribution voltages:
http://www.cooperindustries.com/con...urces/library/201_1phTransformers/R201902.PDF
http://www.cooperindustries.com/con...urces/library/201_1phTransformers/R201902.PDF
JFletcher
Senior Member
- Location
- Williamsburg, VA
Interesting read. The plant I used to work at took 69,000 and stepped it down to 4160. From there the blowers ran straight 4160; rest of the plant was 480.
Last week POCO came to replace a burnt crossarm on a pole. I thought our overhead was 4160/4800V, but after watching them a bit, I learned it is 19,9. Not sure why as it is an older system and the POCO hasnt run overhead service to residential in 25+ years here.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Nice find.:thumbsup:
kwired
Electron manager
- Location
- NE Nebraska
4160/2400 is a common distribution voltage in small cities/villages around here.
Some of them are planning or already have converted to 12470/7200 though for a couple reasons.
1. load has increased over the years
2. rural distribution is 12470/7200 and this makes it easier to tie into that in emergencies or for temporary situtations.
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