Wood Pole

[SilverArc]

Hi

What is the role of an electrical engineer in relation to specify wood or steel poles for distribution of power in as compared to a structural engineer.

I have a riser pole from a substation yard that will be taking one 750 MCM cable and then it will be a run of approx. 1 km at 13.8 KV.

I dont know, where to start and what should I ask the structural engineer. Could you advise me, where can I find some information about 15 KV wood poles.

Thanks

 

[stephenw22]

I'd imagine that you'd need to let the structural engineer know how many kg/km the cable weighs, the cable diameter (for wind and ice loading), the cable's strength (for wind and ice loading), the minimum height that it needs to be mounted at, if there are any unusally large spans to cross (a stream, river, valley, etc.).

You could also try contacting your local utility to see if they have standards already created for that type of line design. If you can purchase an engineered standard from them, it might save you in the long run.

 

[BJC]

Go to this page and download 1724E-152
Ther is other good information on that page.

http://www.usda.gov/rus/electric/bulletins.htm

 

[vtpower]

Just FYI as well, a 750MCM, 15KV Riser on wood pole is a fairly commmon installation. There typically is not a whole lot of structural analysis that needs to occurr, unless you are talking an un-guyed structure. We typically use either 45' Class 3 or 50' Class 3 poles.

 

[jghrist]

Many pole and guy loading calculations have been done by electrical engineers. The RUS guides (see link in BJC's post) include everything you need to know to analyze the pole and guy strength in accordance with the NESC (if you are in USA).

It certainly wouldn't hurt to have a structural engineer review your work, but many design decisions like using 10% of pole plus 2' for embedment depth are empirical more than analytical. You may get flack from structural engineers who are not used to designing wood pole lines.

There may be considerations in some states if the drawings have to be sealed by a PE and your specialty is not structural.

 

[alehman]

jghrist hit the nail on the head. Find a local utility construction standards book or better yet, pick the brain of one of their engineers.

There are tried-and-true methods for performing these calculations if you are outside of the standard configurations, and commercial software is available.

A long time ago I had a structural engineer look at some pole loading calcs and not being familiar with the industry methods, and without soil tests, he was not able to provide any useful feedback.

 

[apowerengr]

The cable load is insignificant in sizing the pole length and class. You need to know the overhead conductor size & design tension, standard guying materials, available guy lead length and required spacing for the deadend arm(s), requirements for spacing for a gang-switch or disconnects (if applicable), desired neutral location, required ground clearances in the first or adjacent spans (crossing streets, railroad tracks, etc.?) and size the pole accordingly. Length driven by spacings and clearances, pole class driven by guying requirements and conductor/loaded tensions. Pole material driven normally by standards or accessibility.