Overhead power lines touching UFB cable

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timmmay

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#164244 3-Feb-2015 07:29

Short version: is a UFB cable touching a power line a problem? In the wind all three cables all get tangled. I know UFB cables aren't made of metal, but one cable could physically wear the other out. I'm really after the opinion of people who have significant knowledge in the area, rather than "hey that can't be good" type posts.

Click for larger version

Longer version: my neighbor called me up and said he'd noticed the power lines to both our houses had gone slack. I'd co-incidentally noticed that the power pole looked funny or on a slight lean earlier in the day but hadn't thought much of it. I called the power company fault line (just in case), told them about it, they sent a guy out immediately who said:
- "Nah it's no problem, there are poles on much worse leans than that", and
- "Nah those cables hitting each other isn't a problem unless your power or internet starts going out".

My neighbor (an electrician) didn't think the cables hitting was a great idea, hence I'm asking for further opinions.

Here's the lean on the pole - apparently not an issue

Click for larger version

Inphinity

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#1230177 3-Feb-2015 08:26

Based on experience with fibre and power cabling in data centre environments (which, yes, differ slightly from this situation), I don't see any real technical issue with it provided the insulation on both is in good condition. Fibre is immune to electromagnetic interference issues, and is non-conductive (though I imagine those sort of overhead lines have a support/strength run that may be braided steel). The biggest issue I can see (and it's hard to tell from the picture) is if the slack power cable could wrap itself in such a way that it is putting tension on the fibre cable, pulling it sideways - that could potentially damage the fibre.

timmmay

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#1230181 3-Feb-2015 08:37

Inphinity: Based on experience with fibre and power cabling in data centre environments (which, yes, differ slightly from this situation), I don't see any real technical issue with it provided the insulation on both is in good condition. Fibre is immune to electromagnetic interference issues, and is non-conductive (though I imagine those sort of overhead lines have a support/strength run that may be braided steel). The biggest issue I can see (and it's hard to tell from the picture) is if the slack power cable could wrap itself in such a way that it is putting tension on the fibre cable, pulling it sideways - that could potentially damage the fibre.

I guess the power cables could put a little bit of force onto the UFB cable, but the UFB cable seems fairly well anchored. I know the cables are likely to interfere, it's more the physical side I'm wondering about, like you say.

Aredwood

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#1232227 6-Feb-2015 14:57

See if you can find out if there is a steel wire embedded in the UFB line. If there is then the power cable will induce voltages into it. (Same principal of how a transformer works) This is only an issue because the phase and neutral to your house are separate cables. If you had a single cable (with 2 cores) for your power. Then the fields from the phase and neutral would cancel out.

DarthKermit

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#1232231 6-Feb-2015 15:20

timmay, is it the phase or neutral wire that's touching your UFB? The phase wire should have a pole mounted ceramic fuse holder.

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Gozer

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#1232234 6-Feb-2015 15:33

The consensus seems to be it'll probably be fine.
What I would really go on is how you and your neighbor feel about it.
If you'd be happier with it fixed then the lines guy has already told you what to report.

I cant see as it would take them much to put a bit of tension back in the lines.

Niel

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#1232238 6-Feb-2015 16:11

The first couple of meters of power line from your house must be insulated, because it needs to be safe for when you work on your roof/spouting. Perhaps yours is insulated all the way? If that is the case, then it does not even matter if the UFB was bare copper. However, I doubt it is insulated all the way. But I would expect the attachment to be adjacent the neutral cable and not phase (just and opinion, who knows what installers do). You can call the lines company and tell them the cable needs to be re-tensioned as it is dangling and gets entangled.

Just re-reading your post, I notice you say the 3 cables get entangled in the wind so yes, the power cables must be insulated or else you would have fireworks every time wind blows in Wellington (do you sometimes get wind in Wellington? :-).

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InstallerUFB

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#1232239 6-Feb-2015 16:15

There is no metalic component in the UFB Aerial Cables/Tubes (in this case Tube) - Their strenth comes from kevlar threads woven, or more like interlaced around the inner components. The outer sheathing is a poly compond, along with providing protection from the environment, it also gives a low fricton surface.

Unless the two lines are consently rubbing back and forwards against each other (fricton will eventualy break the sheathing down) then there shouldnt be a problem with them touching

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timmmay

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#1232652 7-Feb-2015 18:28

Thanks, think it's OK then :)