Re: Joint utility poles [Telecom]

If a joint pole includes power, there is almost invariably a _ground_
> wire at the very top of things. I shouldn't need to explain why.
In my experience (also in the USA), the opposite is true. High-voltage
transmission and subtransmission lines are indeed protected by a
grounded static wire above power conductors. But distribution lines are
rarely fitted with static wires.
Of course, the MGN (multi-grounded neutral) forms a continuous ground
along the line. But the MGN is usually located below power conductors.
See "Joint Pole" in any recent edition of Newton's Telecom Dictionary.
An expended version of the same definition is at
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In the U.S. (at least, that's the geography of my professional
> knowledge, though the logic would seem to be applicable 'anywhere')
> power is also almost invariably (I don't know of even a single
> exception, but acknowledge that they may exist :) in the topmost
> position, for a couple of solid engineering reasons:
> 1) safety -- nobody has to go past the power to get to any other
> service.
> 2) pole-space efficiency -- power requires more physical separation
> from other services than anything else on the pole. By putting it 'on
> top' you only have one separation interval (below the power) of
> 'unusable' space.
Telcos usually require 12-inch separation between their facilities and
any other facilities on the same pole.
After that, it tends to be -- in "descending" order -- a simple
> matter of the order in which pole space was rented.
Every pole attachment agreement I've ever seen specifies that CATV must
be placed at least 12 inches *above* telephone cables. And since telcos
were usually there first, they have the right to dictate the terms to
the CATV companies.
The 12" clearance requirement provides both companies space for the
lasher -- the device that spins the lashing wire around the strand and
the signal-conducting cables. See
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AND, there's a third, 'practical', reason why power is on top -- it
> is usually the power utility who puts the poles in, in the first
> place. There is almost never a need for multiple services until power
> is there...
Not necessarily. Even in urban areas, telcos often set their own poles
in places where no power pole exists. As you note, many of them are
small short poles ("toothpick poles"). But at least as many are
designed for joint use even if the immediate need is for telco only.
I've often seen telco-only poles with 10 or 15 feet of unused space
sticking up above telco for future power use. (Good thing, too: those
poles provide space for CATV 12" above telco, and still leave space for
power in the future.)
It is *VERY* rare to see power piggy-backed onto phone company poles
> -- in part for the first two reasons mentioned above, and because
> power distribution requires considerably sturdier footing than just
> phone does.
Wes Leatherock responded to that comment:
This is simply not correct. The agreements between power companies
> and telephone companies provide that each company pays rent for using
> the other's poles. In practical terms, they try to keep the ownership
> about equal - half telco, half power company to simplify bookkeeping
> by, as near as possible, cancelling out rental payments to one or the
> other. In some cases this will mean the telco may own a pole used
> only by the power company, or the power company owns a pole used only
> by the telco.
Depends on the local situation.
In the case of investor-owned (for-profit) utilities, Wes's statement in
generally correct: power and telco strive for 50-50 ownership. And, as
Wes notes, there are situations where telco owns a pole used only by the
power company, and where power owns a pole used only by the telco.
But there are exceptions even to that. When I was working in cable TV
in Madison, Wisconsin, we were never quite sure who owned which pole:
some were 100% Madison Gas & Electric; some were 100% Wisconsin
Telephone; some were 50-50; still others were odd combinations like
60-40. Fortunately, it didn't make much difference to us: we just
submitted all pole applications to both companies and let them sort it out.
WisTel's pole records were maintained in a central computer database at
their headquarters in Milwaukee. MGE's pole records were hand-written
in a 3-ring notebook. Guess which one was more accurate.
In the case of municipal utilities, most joint poles are owned by the
utility; i.e., the municipal government. When the city owns the power
distribution wiring, the poles that support it, and the underlying land,
it can pretty much dictate the terms to everybody else.
Robert continued:
More separate [power] strands (especially with multiple branches on a
> common feeder section) translates to greater wind/ice/snow loading
> which means increased lateral stresses as well as the added weight;
> then there is the weight of the transformer well.
True. However, telco cables can be pretty heavy too; I've seen
multipair cables almost two inches diameter. In order to prevent sag,
strands supporting big cables like this have to be placed under high
tensions, often several hundred pounds. Further complicating the
situation, some polelines carry two or more telco cables. An extreme
example:
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Similarly, a bundle of CATV cables can be as much as 2 or 3 inches in
diameter. CATV cables are lighter than telco cables, but their
supporting strands still have to be tensioned to prevent sag.
Add three inches of radial ice and a 100-mph wind, and communications
cables can put a huge lateral force on a poleline.
Neal McLain
Reply to
Neal McLain
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Are there actually installations that can withstand three inches of radial ice? Once the ice passes 0.3 inches here we're heading for a major power and communications failure with ordinary residential streets looking like plates of spaghetti.
Reply to
Tom Horne

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