Working on overhead powerlines

[Russell]

On our ride the other day we passed under some overhead power lines, the big (is it) 50,000v ones and there were gondolas hanging down from the lines in 3 or 4 places each with men working in them.

Inspection I assume, but how do they get them up there and the men in and out.  The line must be shut down???

[matthew]

There are videos on the web of people accessing this sort of thing from helicopters which can be done live.   

[ElyDave]

With the gondolas they shut down one side of the pylon at a time, you may have seen some pylons with red and green flags on them indicating live/dead.

The goldolas are winched up, the men climb the pylons and move the gondolas by hand

[Tim Hall]

If it's down your way, it'll be the Fleet to Lovedean replacement.  As ElyDave says they shut one side off, replace the conductors, then work on the other side. Every time the line crosses a road scaffolds towers are put up with a net betwen them, to prevent cables fallingf on unsuspecting members of the public.  My firm supplied lots of ground anchors to hold the scaffolds down.  There's an example where it crosses the A31 near Alto, for example.  The scaffold in the central reserve has big concrete blocks doing the holding, as there are buried services there, the scaffolds either side of the A31 have ground anchors.

Here's what's going on: https://www.nationalgrid.com/uk/electricity-transmission/fleet-lovedean-overhead-line

[Jurek]

If it's down your way, it'll be the Fleet to Lovedean replacement.  As ElyDave says they shut one side off, replace the conductors, then work on the other side. Every time the line crosses a road scaffolds towers are put up with a net betwen them, to prevent cables fallingf on unsuspecting members of the public.  My firm supplied lots of ground anchors to hold the scaffolds down.  There's an example where it crosses the A31 near Alto, for example.  The scaffold in the central reserve has big concrete blocks doing the holding, as there are buried services there, the scaffolds either side of the A31 have ground anchors.

Here's what's going on: https://www.nationalgrid.com/uk/electricity-transmission/fleet-lovedean-overhead-line

M'Julie and I witnessed this (scaffolds, nets, etc) just past Upchurch, when we used the FNRttC route to drive down to Whizzy Belle a couple of Fridays ago (The M2 was banjaxed traffic-wise, as was the A2).
Despite the 'Road Ahead Closed' signs, there was nothing to suggest any work was taking place at the time.
Probably too hot for work.

[ElyDave]

Interestingly, those conductors are Al rather than Cu, and national grid were working on getting them recycled into new conductors as part of a circular economy gig. One of the more tricky issues was degreasing the old ones, the grease being needed to allow the expansion and contraction with temp differences.

[rafletcher]

They’re also, I believe, hollow, as at those elevated voltages the charge is mainly carried on the surface of the conductor.

[hatler]

Al 'cos lighter than Cu I would think.

[ian]

Al is a lot cheaper than Cu too.

In the far-east, powerlines are maintained by specially trained monkeys. They brachiate between pylons.

[Russell]

Precisely that Tim, a few miles south of Fleet substation in fact.

All very interesting.

[Kim]

They’re also, I believe, hollow, as at those elevated voltages the charge is mainly carried on the surface of the conductor.

AUIU they have a steel or composite core, which allows them to run hotter (ie. at higher current) than pure aluminium or copper without excessive sag.  The skin effect is a function of frequency, not voltage.

Al 'cos lighter than Cu I would think.

Yep, you can increase the area of the conductor to the point where it has the same resistance as copper, and still win on weight, which means less expensive pylons.


(Personally, I get scared of anything higher than about 36 voles.)

[nobby]

(Personally, I get scared of anything higher than about 36 voles.)

Very wise. Voles have got sharp teeth but they are not as aggressive as a yellow necked mouse when trapped although 36 of them would warrant a careful approach 

[cycleman]

Send in the 🐈🐈🐈🐈🐈🐈🐈🐈🐈🐈🐈😉

[DaveJ]

The big ones are probably 400kV.  Wow!

[toontra]

Pylon-related - a great TV documentary from a few decades ago about how they get painted and the guys who paint them:

https://www.youtube.com/watch?v=EhIf6163H4c

[Cudzoziemiec]

4 lakh voles!