Typo in textbook??

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K8MHZ

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"This voltage must be stepped up using transformers to higher voltages, 345 kV for long-distance transmission or 500 kV for short-distance transmissions, and it may be increased to even higher voltages, up to 765 kV, for transmission over the longest distances."

This is the first release of a new book on wind power generation, college level.

It would be nice to hear some comments before I bring this to the attention of the instructor.

Thanks.
 

Little Bill

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"This voltage must be stepped up using transformers to higher voltages, 345 kV for long-distance transmission or 500 kV for short-distance transmissions, and it may be increased to even higher voltages, up to 765 kV, for transmission over the longest distances."

This is the first release of a new book on wind power generation, college level.

It would be nice to hear some comments before I bring this to the attention of the instructor.

Thanks.

Are you saying the 345 kv and the 500 kv should be reversed?
 

K8MHZ

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Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Are you saying the 345 kv and the 500 kv should be reversed?

Well, that's what I am thinking, but my background is not distribution and transmission.

Sometimes reality does not seem logical until further understanding. Take, for instance, our conductor fill percentages. One conductor can occupy up to 53 percent of the cross section. For two, it drops to 31 percent. For over 2, instead of dropping again, it goes up a little to 40 percent.

Now, I know the reason why this is, but to an outsider this may appear as a typo.

This is not the first time I have found errors in text books. As such, I know that just my suspicion is not enough to warrant certainty. I have found over the years that the best way to approach the situation is to have as much back up documentation as you can before approaching the instructor.

The documentation not only would provide support, but illustrate to the instructor that you are taking the issue seriously enough to have done research on the subject.

So yes, to me of the levels should be reversed.

Since I'm not a linesman I don't really know were to look for documentation to support my suspicion (or not).
 

charlie b

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Forget the numbers, and look at the words: long, short, longest. Those are out of order. You don't need any backup documentation for that.
 

K8MHZ

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Forget the numbers, and look at the words: long, short, longest. Those are out of order. You don't need any backup documentation for that.

Thanks, but I don't think that presents much of a case.

For 2 wires we get 31 percent to fill. For three we get 40 percent to fill. For one wire we get 53 to percent fill.

That is half 'out of order' too, but nonetheless a fact.
 

mivey

Senior Member
I agree with charlie b. My background is distribution and transmission.

Now sure of the context but the 765 kV is a little dated as they are much higher now. His use of short-distance is relative I guess to where he is from. Hard to tell from a snippet.
 

K8MHZ

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I agree with charlie b. My background is distribution and transmission.

Now sure of the context but the 765 kV is a little dated as they are much higher now. His use of short-distance is relative I guess to where he is from. Hard to tell from a snippet.

Can you provide me with a link that covers the distribution and transmission voltages and the distances they are intended for?

I also thought 765 was a low max. I do know that up to a million volts DC are used to tie grids together.
 

mivey

Senior Member
Can you provide me with a link that covers the distribution and transmission voltages and the distances they are intended for?

I also thought 765 was a low max. I do know that up to a million volts DC are used to tie grids together.
I have no link but I'm sure a search will provide as many opinions as you want. The conductor size and voltage is an economic evaluation and each utility will make their own decision. It is not strictly a mileage thing but also a function of how much power you intend to push down the line (sound familiar?).

You could conclude that the voltages the author used did not range low enough or high enough but it would be hard to know as we have no context. On the low side, we have transmission in the 46 and 69 kV ranges as well (also called sub-transmission). But the author did not cover 115 kV or 230 kV either which we call transmission around here.

Another question that must be addressed is if there are any taps off the line. The higher voltages are strictly used to get from one transmission point to another without any retail loads tapped in. Maybe the author was talking only about those type voltages. I really don't know.

At any rate, I think charlie b was right. Even if you knew very little about G&T, logic would tell you he was right based on the text snippet you provided.
 

handy10

Senior Member
Textbook errors

Textbook errors

You don't have to have documentation to ask the author if there is an error. Just ask him if the sentence is meant to read "short, long, longest." Authors usually don't mind honest questions, especially when they are not silly (yours would not be a silly question).
 

mivey

Senior Member
Can you provide me with a link that covers the distribution and transmission voltages and the distances they are intended for?
Here is one I found for EHV, which seems to be the topic the author might have been discussing:

http://www.aep.com/about/transmission/docs/transmission-facts.pdf

While it is also based on load, AEP gives an example for both a fixed distance and a fixed load.

Voltage Class | Loadability (@300 Miles) | “Reach” (@1500 MW)
--------------------- ------------------------ ------------------
765 kV Single Circuit | 2200 – 2400 MW | 550 Miles
500 kV Single Circuit | 900 MW | 140 Miles
345 kV Double Circuit | 800 MW | 110 Miles
345 kV Single Circuit | 400 MW | 50 Miles
 

charlie b

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For 2 wires we get 31 percent to fill. For three we get 40 percent to fill. For one wire we get 53 to percent fill. That is half 'out of order' too, but nonetheless a fact.
And I suspect that everyone who reads that for the first time is confused by the "apparent error." I certainly was. But when someone explained to me the notion of conductors becoming jammed inside the conduit while you are trying to pull them through, it all made sense. Perhaps this author has a reason for writing that text in that order. You can ask. Asking is free.

 

K8MHZ

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Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Here is one I found for EHV, which seems to be the topic the author might have been discussing:

http://www.aep.com/about/transmission/docs/transmission-facts.pdf

While it is also based on load, AEP gives an example for both a fixed distance and a fixed load.

Voltage Class | Loadability (@300 Miles) | ?Reach? (@1500 MW)
--------------------- ------------------------ ------------------
765 kV Single Circuit | 2200 ? 2400 MW | 550 Miles
500 kV Single Circuit | 900 MW | 140 Miles
345 kV Double Circuit | 800 MW | 110 Miles
345 kV Single Circuit | 400 MW | 50 Miles

Perfect!

There is also a bunch of great info in that PDF.

Thanks, I appreciate it.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
And I suspect that everyone who reads that for the first time is confused by the "apparent error." I certainly was. But when someone explained to me the notion of conductors becoming jammed inside the conduit while you are trying to pull them through, it all made sense. Perhaps this author has a reason for writing that text in that order. You can ask. Asking is free.

The best way to explain the conductor fill anomaly is to blame it on geometry.

One conductor is a perfect circle. Two make a sort of and oval, the least like a circle with the most empty space per occupied cross sectional area of all. Three conductors and up start becoming more like a perfect circle again.

The book is in it's first printing. Since I found an error in the first 5 minutes of glancing through it I have a sneaking suspicion that I will find more as we delve deeper into the text. I will keep a running errata sheet. When I am done I may attempt to contact the author of the book. I will also give the instructor of the class a copy of my findings.
 
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