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Child Item

How much voltage do Telephone lines carry on the poles?

Andy From Sligo

some years ago i was going to a dentist appointment and someone ahead of me had hit a telephone pole at the side of the road and it was across the road blocking it so no-one else could drive past. The wires were intact and covered in PVC black insulation.

Some other people pulled up in their cars and I said 'shall we all try and move this pole to the side of the road so people can get through?' - no a couple of them said they might be live , or electricity wires. I convinced them they weren't by showing them the power lines in the field across the road which the poles and the wires looked different and the ESB poles had the insulators on them at the top of the pole, the telephone pole just had the insulated cables on them. so we moved it , cables an all to the side of the road in a ditch … and i made my dentist appointment on time and other cars could use the road again.

So this evening I see this posted on linkedin from OpenEir:

it got me thinking , well the telephone cables on the wooden poles at the side of the roads look to be all insulated in black insulation (copper and fibre optic cables) an that if you cut or touched a bare copper telephone cable i thought they were around something like 48v DC or something like that - I dont know how many amps, and I sort of remember the old saying 'volts jolt …. Amps kill' or something like that … so wondering can someone enlighten me if you do find a telephone pole down in a storm and the insulation has been cut /or the cable has been cut - what kind of shock are we talking of getting if you grabbed hold of it?

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Comments

tphase

Phone lines carry 48V DC, don't think you'd get much of a tingle out of it.

Capt'n Midnight

Up to 400 KV if a power cable has fallen on it further down the line.

Overhead power cables are not insulated. And overhead phone cables aren't insulated against power cable voltages.

Even if there's no contact with mains the AC Ring Voltage is on top of the DC. So could be 100V or more when ringing.

Andy From Sligo

https://www.boards.ie/discussion/comment/123122146#Comment_123122146

blimey - i never even though of a scenario of a 400kv power line falling onto telephone wires! - hate to think what that would do when it comes up your phone socket and into your corded phone or ADSL router … or would it just explode the telco cabinet to bits first?

tphase

https://www.boards.ie/discussion/comment/123122274#Comment_123122274

I'd have thought it highly unlikely phone cables would be run on poles under or even close to any high voltage power lines. That's not to say live power lines couldn't come into contact with phone cables but, going by the number of cables that have been on or close to the ground around Connemara for months/years, Eir mustn't consider it a major safety issue

eronayne

https://www.boards.ie/discussion/comment/123122115#Comment_123122115

Yea typically 48v, or if my memory serves correct I seem to recall it is technically -48v. you wont feel anything at that voltage, however it pulses up to 100v when a ring signal is been sent down the line.

ISDN also runs at a higher voltage also enough to give you a tingle but wouldn't cause much harm. more dangerout for the lad standing behind you watching you lift the cable in case you elbow him in the face when you yank your hand back after getting a tickle.

L1011

https://www.boards.ie/discussion/comment/123320741#Comment_123320741

once had to try find an unmarked ISDN line on a frame and figured it out by which one tingled. Not the most safe way to do it!

The Cush

A few years ago I was relocating my brother's telephone line to a power room. I accidentally shorted my arm between the incoming line and the copper pipework, got a bit of a jolt in the arm, I survived.

magicbastarder

https://www.boards.ie/discussion/comment/123122146#Comment_123122146

i suspect if a phone line designed to carry 48v was carrying 400kV, you'd know about it long before you got to touch it?

ItHurtsWhenIP

https://www.boards.ie/discussion/comment/123321515#Comment_123321515

A power room you say … 😏

PixelCrafter

The issue is that they can be in contact with ESB lines when storm damaged and then potentially be carrying dangerous voltages.

Telephone lines in Ireland run at at most -48V DC and have a ringing signal that's 75V 25Hz often applied across both wires, out of phase (balanced ringing). The network voltages aren't particularly dangerous - the fault voltages in a storm / damage potentially could be.

ISDN uses something like 100V DC between the exchange and the terminal.

They are also strongly underlining that people might confuse their overhead infrastructure and live ESB cabling as most people will not be all that aware of which is which.

beachhead

Ah,the days when tingling was free.220 was always better for waking you up.

Andy From Sligo

https://www.boards.ie/discussion/comment/123322165#Comment_123322165

I always differentiate over here in Ireland (most probably wrongly on my part) and most of the time driving along the rural road (as a passenger of course) I haven't been wrong that the telephone lines look a whole lot different to the network ESB power lines (well to me anyway) - telephone poles/lines made even now more easier to seperate from the ESB lines now because a lot of the telephone poles now have the fibre optical broadband lines with the fibre optic splitter boxes with the fibre cable wrapped up in a loop every now and again on a post in between a few poles… and the lack of porcelain insulators in most cases, and PVC black covered cables attached to the pole on brackets and affixed parallel to the pole - the way I see the difference on the ESB poles are normally (to me) clearly un-insulated most of the time 2 wires running opposite at the top of the pole , on porcelain insulators with a 3rd higher up from the other 2 wires another wire (is that the earth wire or an extra live phase wire for 3phase electricity I am not sure about that, but I think its earth) - and then of course the other ESB wire on galvanised pylons in the fields. - I don't seem to notice any ESB power lines running at the edge of the roads also, mainly just telephone/fibre cables at the edge of the road poles and not normally ESB poles and just the ESB wiring going across the fields.

PixelCrafter

Most urban overhead ESB lines carry Siro fibre these days and not all electrical wires are bare and on insulators - there’s loads of quadruplex twisted insulated 230/400V lines used in distribution systems. If you look in any urban area wheee Siro is present you’ll see distribution points that look very similar to OpenEir, but they’re on live 230/400V ESB distribution poles.

Also a lot of OpenEir rural copper lines are also quite think multicore bundles that serve ribbon development along roads — that can be easily confused with power lines. They just look like black insulated overhead lines.

Also the clearance between ESB infrastructure and phone lines often isn’t enormous — in a storm it’s not all that unlikely to encounter contact.

The other issue is most people don’t necessarily understand the difference in how they look. A lot of people, you even see it a lot in news coverage will describe ESB local lines as “telegraph wires” and all sorts of stuff. Eir is just taking the view that people are mostly not paying much attention details like that.

In general the eir network will become easier to maintain and electrically safer to work on when the copper is gone. It simplifies the wiring by a long shot — just far less off it , removes many of the maintenance issues around corrosion of conductors etc, no longer as much need for have to have pressurised (with air) underground cables to prevent water ingress — gets rid of copper conductors entirely —

Windowsnut

ESB also use black coloured bundled pvc covered conductor on its LV network, it is not all bare conductors and insulators.

You should always treat utility infrastructure as live.

Unlike the RCD protection in your home, electrical networks generally do not have such protection devices and may be energised and if dead, could be re-energised by reclosers temporarily during fault restoration works.

Charles Babbage

In the old movies, the bad guys always cut the phone line and I could never understand why the hero did not just reconnect them again!

Capt'n Midnight

https://www.boards.ie/discussion/comment/123424422#Comment_123424422

https://en.wikipedia.org/wiki/25-pair_color_code

ESB poles don't have footrests / stirrups. Most utility poles have a numbered label near eye-level

Andy From Sligo

https://www.boards.ie/discussion/comment/123424403#Comment_123424403

you should but at the roadside on poles you can still tell the difference a mile off between telephone poles/infrastructure to a ESB pole/infrastructure … well I can anyway where we live in the shticks - and also if they dont already the ESB should be putting metal sign on all their wood and metal posts with ' Danger - High Voltage' which I have seen on ESB poles before. Plus as I say 9 times out of 10 I have personally seen , running parallel to the country roads (and where the cables have been laying down in ditches and in the fields and wonky poles that are not vertical, they have always been, the ones I have come across at the edge of the road, Open-eir Telephone posts and cables.

Windowsnut

all poles do have danger notices, but some times mud will cover them or ivy over time.

most of the time the two networks are clearly identifiable.

emaherx

https://www.boards.ie/discussion/comment/123424615#Comment_123424615

I see high voltage warnings on Eir poles recently too, where the Eir cables pass under ESB lines.

But yes the 2 networks are easily identifiable, however it's probably best advice to anyone who may mistake them to stay clear of both, especially with fallen lines after storms.

Windowsnut

better safe than sorry….

Charles Babbage

https://www.boards.ie/discussion/comment/123424437#Comment_123424437

For a bonus mark, which side of the road here has BT poles and which was Eir poles?

Andy From Sligo

https://www.boards.ie/discussion/comment/123426558#Comment_123426558

I would need to zoom out and have a complete view of the fields , how the wiring is terminated to the houses , what equipment is attached to poles (like boxes , or loops of wires and porcelain insulators ) to make a more definitive assumption …. but even in that picture as it stands to me strangely they on both sides of the road look like telecommunication poles to my untrained eyes .

Andy From Sligo

https://www.boards.ie/discussion/comment/123424685#Comment_123424685

very bad planning if openeir cables pass under ESB lines! - never seen that myself , but if you say thats the case and does happen who am I to argue

Charles Babbage

https://www.boards.ie/discussion/comment/123429355#Comment_123429355

They are both telephone poles, but from two different administrations. Hence the bonus mark.

emaherx

https://www.boards.ie/discussion/comment/123429589#Comment_123429589

I'm going to guess the wonky poles belong to Eir? Not sure I've seen too many Eir poles that tall. (and not many that straight 🤣)

emaherx

https://www.boards.ie/discussion/comment/123429362#Comment_123429362

There is plenty like that around here.

dam099

https://www.boards.ie/discussion/comment/123429362#Comment_123429362

Unless both networks consisted of a single line each running parallel they are going to have to cross each other somewhere.

tphase

https://www.boards.ie/discussion/comment/123429822#Comment_123429822

Phone lines are usually buried underground when they cross power lines

Charles Babbage

https://www.boards.ie/discussion/comment/123429599#Comment_123429599

This may well be correct, but a perceptive border dweller will also notice other details.

https://www.boards.ie/discussion/comment/123429963#Comment_123429963

Is it fair to say that lines are usually underground when 10Kv lines or higher pass over, but not for local low voltage lines?

emaherx

https://www.boards.ie/discussion/comment/123429971#Comment_123429971

I know of a few places where telecoms lines run under high voltage lines.