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Planned power cut

I will have no power tomorrow. Scheduled from 9am to 4pm, which is conveniently when I'll be at work. ☺

I'll take what remains in the fridge (some milk, some yoghurt, some cheese) and put it in a cool box. I have already put two Evian bottles, filled with well water, in the freezer part to help keep everything cold tomorrow.

Then I'll leave the fridge door open and let it defrost. It isn't a proper fridge-freezer, it's a fridge with a one-star icebox up top. One star is better than many, but it's hardly the usual -18°C one would expect from a freezer.
Some day I plan to get a little table-top freezer, but it's not really a priority. I've done without for twenty-odd years, so...

Once that's sorted, and I have got everything together for work and tea made, I'll shut down the Pi and then throw the main switch. Just cut off everything.


Why the power cut? Enedis sent me a letter talking about amelioration of the network blah blah. I didn't bother reading their feelgood explanations, it was just simpler to look at the top of the lane.

I should have taken the Mi10T for the extra-wide-angle, but alas I didn't think of that.

Electric works - overview
Electric works - overview.

Here's what I see walking up. I can see a new pole, but I recognise that truck. Shame I can't ask him to punch a hole in the rock out on Western Wilderness so I can plant the odd little pine tree. I bet he would if it was the big Hellfest dude. He put in the new poles for our change of supply, and let's just say we had appreciation for each other's choice of music (I'm currently listening to Within Temptation on PPN as I write this). I'd love to go to Hellfest (it's in Clisson), but... people...

Anyway, passing above this is a medium voltage (I think about 15kV? it's an "HTA" class) line that works it's way down the road. On the ground are a lot of cables.

Electric works - big-ass wires
Electric works - big-ass wires.

It doesn't make sense to run a new line from here using underground cables and then go back above ground. So what I think they're going to do is replace the post with a terminator post, run the cables underground from this point on, and tear down the overhead line.
I suspect Enedis are fed up with all of the hastily-thrown-up exposed-wires lines around the landscape. It's dangerous for people (children with kites, for instance) as well as for wildlife. I've already seen twice on this line a dead large bird that spread it's wings and arced across two wires in a rather terminal way.
Back in August 2016, I was only getting 129V out of one phase for exactly this reason. A bird shorted out the line in a way that was terminal not only to the bird, but to the line. Apparently what was left (of both) was quite a mess.

There's a big programme, part of the Linky smart meter upgrade, to tear down all the horrible low voltage (230V) wiring that is supplied by bare exposed conductors, and replace all of that with a twisted bundle of insulated wires. That's what I have now, and the difference was massive. My 230V was closer to 218V, and it tended to dip below 200V when I put the kettle on (when I was making a hot water bottle for mom, I used to switch it on and go back and talk to her, we'd know it was finished when the lights suddenly got a bit brighter). Since the Linky, and the new hookup, it's been a pretty solid 230V.
I wasn't aware of doing the same for the medium voltage stuff though, although I guess it makes sense. I just hope some twatty farmer doesn't plough through it, as that would be one hell of a bang.

This looks like the tap-off from the overhead lines to the ones going down. It looks like they might also be placing a pole-mounted switch there.

Electric works - tap-off
Electric works - tap-off hardware.

And here's a close-up of the top of the pole. I could only see three sets of glass discs, so this will surely be an end-of-line rather than a spur.

Electric works - pole top
Electric works - pole top.

I like the big "this is wired up - DANGER OF DEATH!" sign on the top of the pole. Of course, I went and touched it. I'm still here...


The network is not one fixed voltage. There are three classes of cables.

  • THT/HTB: large pylon, usually with conductors balanced on each side, and probably six of them.
    Typically 400kV.
  • THT/HTB: largish pylon, usually with three conductors and one passing through the middle of the pylon.
    Typically 225kV.
  • HT/HTB: smaller single-frame pylon, may have three or six conductors held out on short stubby arms.
    The taller ones carry 90kV, the shorter ones carry 63kV.
  • MT/HTA: usually a concrete pole with three wires mounted horizontally, common all over the countryside.
    Nominally 20kV, but can be 10/13/15/20kV depending on when the installation was made.
  • BT: a shorter concrete pole carrying either four bare conductors one above the other, or a twisted bundle of black wires.
    This is 380V, the domestic supply.

Why 380V? That's the voltage between phases. It's 230V from phase to earth.

There's a little trick you can use to determine the voltage passing through any given pole. Well, some carry a little plaque that tells you the pylon number and its tension (voltage).
Or, look up and count the little glass discs.

  • None - it's a low voltage (230 if two wires or 380V if four) supply.
  • 2 or 3 discs - about 20kV (10/13/15/20kV).
  • 4 to 6 discs - 63kV.
  • 9 discs - 90kV.
  • 12 to 14 discs - 225kV.
  • 19 or 20 discs - 400kV.
The latter two may have them ganged as two parallel rows.



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David Pilling, 20th January 2022, 02:28
Cue video standing under power line holding up a fluorescent tube. 
Wellies be your friend. 
J.G.Harston, 22nd January 2022, 01:42
Where I live is surrounded by a national park on three sides (and the sea on the other side). A few years ago NEDL decided to improve the landscape by buring the main power feeder across 40km of moorland. For about six months as I drived over the moors there would be a trench in thr road that moved along each week. 
One oddity is where the power lines cross a small river in the middle of the moors, instead of tunnelling under the river, or running a conduit under or next to the road bridge, they brought the power lines back above ground with one of your terminator poles, string the lines about 40m across the river, then dived back underground. 

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