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Maximum Transmission Line Span

Maximum Transmission Line Span

Maximum Transmission Line Span

(OP)
Is there a code or requirement depicting how long a transmission span can be?

In particular for a 345kV tranmission line?
 

RE: Maximum Transmission Line Span

Not in the USA, as long as strength and clearance requirements are met and due consideration is made to aeolian vibration concerns.

RE: Maximum Transmission Line Span

(OP)
jghrist,

Just to clarify, you are referring to the span and not the transmission line length itself. Correct?

My question was regarding the span between two supports and how far can a transmission span go without requiring another support.


 

RE: Maximum Transmission Line Span

Yeah, I'm sure that's what he meant.  I've seen spans in excess of a mile, but not very often.  1/5 to 1/4 mile spans are not uncommon, but it all depends on site conditions.

RE: Maximum Transmission Line Span

Right.  Span lengths of river crossings can get very large.  Also in the mountains across valleys.
 

RE: Maximum Transmission Line Span

Here's one that I found impressive from the ferry: http://maps.google.com/maps?ll=48.516016,-123.54032&z=16&t=h&hl=en

The two lines are invisible, but join the visible rights of way. One line makes a 90 degree turn up hill prior to crossing. The other crosses much lower without turning north first. Equivalent height mid-span, conductor size, and towers. I'm guessing the lower line may be using one of the new low sag cores. From the scale, it looks like it exceeds 8000.  
 

RE: Maximum Transmission Line Span

Steven, your link is the same as my first link, a bit over 3300 ft.  Probably not what you meant to post.

RE: Maximum Transmission Line Span

Nice.  Measuring it in Google Earth it is over 10,300ft for the east span.  Zooming in in Google Earth, you can see the conductors; two circuits, individual towers for each conductor, 75ft spacing between phases, and lots of marker balls on the spans.

RE: Maximum Transmission Line Span

(OP)
Wow! pretty cool!

Only us engineers would find it to be cool :)

RE: Maximum Transmission Line Span

Looks like 17,638 ft is doable.
http://en.wikipedia.org/wiki/Ameralik_Span

When we recently replace a 6200ft span, the only electrical code requirement that caused us grief was the NESC conductor tension limit of 25% rated tensile strength.  The limit is a decent rule of thumb to prevent vibration damage in typical spans.  Although we had an extensive damper system designed, we ended up having to use a stronger cable just to meet the NESC requirement.

http://www.ci.tacoma.wa.us/power/towertalk/Images/Historicals/pictur16.jpg
 

RE: Maximum Transmission Line Span

Greenland.  This on is 5,376 Meters long.
What  do they do with all that power in Greenland.  There must be a mine some where nearby.
http://en.wikipedia.org/wiki/Ameralik_Span

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