How can one distinguish between a 69 kV vs. a 138 kV electrical
transmission line? For instance, in looking at a line how many wires
would 69 vs. 138 kV have?

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Request for Question Clarification by pafalafa-ga on 03 Mar 2005 13:21 PST

For power transmission, size counts (the bigger the kV, the heavier the wires).

Is this the sort of visual information you need:


http://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/transmission_lines.html



If not, let us know in a bit more detail what you're after.  

Thanks.

pafalafa-ga

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Clarification of Question by rancher2-ga on 04 Mar 2005 04:53 PST

I had found the website you listed, and it is good but it doesn't
answer my specific question.
    I need to distinguish 2 different transmission lines crossing my
property.  Both lines have 2 wooden poles, a cross arm near the top. 
However one of them has 4 wires, and I know it is 138 kV.  The other
is similar but has only 3 wires.  Is there a difference in the line
voltage between the 2 ?  If so, does the 3 wired line carry 69 kV or
sme other voltage?

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Request for Question Clarification by pafalafa-ga on 04 Mar 2005 12:12 PST

There are an awful lot of variations in the equipment, layout and
dimensions of these things, so it's hard to give an unambiguous
answer.  The number of wires, though, doesn't seem to be a reliable
indicator, as far as I can tell.

However, here are the specs (with illustrations) for equipment from
one company that provides switches for overhead transmission lines:



http://www.seecoswitch.com/dimensions_1g069.htm
Dimensional Data 15 - 69 kV
 


http://www.seecoswitch.com/dimensions_1g115.htm
Dimensional Data 115 - 230 kV


The key difference is largely in the separation between the switches
(dimensions G and H in the drawings) -- a lot more clearance is needed
for 138kV than for 69kV.


If the clearances on your two poles are pretty similar, I would guess
the voltage they are carrying is similar as well.


Let me know if that helps.


pafalafa-ga

You might be able to tell them apart by the size of the insulation
standoffs. The 138 kV lines should be held apromaxly twice the
distance from the poll as the 69 kV ones. You could also ask the power
company, I can't think of why they wouldn't tell you.