
Robot wraps fiber optic cables around existing power lines - Lexodusk
https://eandt.theiet.org/content/articles/2020/07/robot-wraps-fibre-optic-cables-around-existing-power-lines/
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mmmBacon
Overall, it’s an interesting project and I hope they can solve all issues for
a real deployment.

They don’t mention the length penalty that comes from wrapping around the
cable or any impact of loss to fiber itself. Given the helical pattern, I’d
imagine that they are adding substantial length to any distance they need to
achieve. Generally you have about 20dB of loss before you need an amplifier or
a terminal node. A typical number for field installed fiber is 0.25dB/km. So
there’s some distance penalty needed here. I’m not clear on how you’d add
amplifiers to these routes or if they are simple short hops.

Generally regular SMF-28 has a bend radius of 25mm. This is partially for loss
reasons as bends below this radius induce loss and partially because bending
fiber below that radius creates micro cracks in the fiber. The micro cracks
can spread with time and cause the fiber to break. Given the rather large CTE
mismatch between the power cable and the fiber cable, the 2 will expand at
different rates with temperature, putting additional stress on the fiber,
potentially leading to failure.

It’s possible to have a less bend sensitive fiber but it’s generally used more
in specialty applications and not as transmission fiber. So it’ll be more
expensive per km.

Along the lines of mechanical failure, it would seem that there would be the
potential for abrasion between the power cable and the fiber cable jacket.

Finally, it’s a little unclear how repairs would be made. Doesn’t seem very
safe to have to splice the fiber on a live cable like this.

~~~
rini17
It's medium voltage lines which are up to tens of kilometers long, not high
voltage hundreds of km. The spans between pylons are also much shorter than
HV, so adding slack to allow for CTE mismatch seems doable without excessive
abrasion.

On the illustration the winding is very sparse, it definitely does not look
like running into minimal bend radius problem or adding much length.

~~~
mmmBacon
I’m not sure what the diameter is of these cables but I found a data sheet
that shows MV (33kV) cables are <50mm in diameter. If that’s true then, the
bend radius is <25mm.

If the winding is sparse, let’s say 1 turn every 1m on a 38mm diameter cable,
then the amount of length added will be ~1% of the total linear length
(neglecting the cable sag). So the amount of added length due to winding it
will negligible.

At 1000 bends per km, if we assume loss is 0.001dB per bend, then we’d add 1dB
per km.

[http://www.prioritywire.com/brochures/Medium%20Voltage%20Pow...](http://www.prioritywire.com/brochures/Medium%20Voltage%20Power%20Cable.pdf)

~~~
agseward
Wouldn't the bend radius only be <25mm if you were winding very densely? At
sparse winding, you aren't actually bending it much.

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tallanvor
I know it's not really relevant to the meat of the article, but I can't trust
any of the numbers listed in the article. They claim that "Just 28 per cent of
people living in Africa are internet users and two-thirds of those are located
in South Africa."

If we take the population estimates of just 4 countries: Nigeria (206
million), Ethiopia (109 million), South Africa (60 million), and Kenya (47
million) we get 422 million people. 28% of that is 118 million, and 2/3 of
that is 79 million. Clearly South Africa can't have 79 million internet users
if they only have a population of about 60 million.

~~~
dmix
Found a source Google cited for the 28% figure in this [1] article. Not
claiming it's accurate since they only source their own "ITU estimates". I
also don't see a mention of "South Africa" in the stats:

[https://www.itu.int/en/ITU-D/Statistics/Documents/facts/Fact...](https://www.itu.int/en/ITU-D/Statistics/Documents/facts/FactsFigures2019.pdf)

The same PDF mentions "3G coverage in Africa at 79.5 percent". So I guess that
is not being counted as internet. Must be broadband?

[1] [https://www.nytimes.com/2020/07/07/world/africa/google-
loon-...](https://www.nytimes.com/2020/07/07/world/africa/google-loon-balloon-
kenya.html)

~~~
sgt
Perhaps it is an estimate of Internet users using a conventional computer. I
am pretty certain that the figure must be higher than 28% these days as pretty
much everyone has a smart phone, even poor people in the slums of Kenya. There
are however still quite a few feature phones out there though, often with
keypads nearly worn down to the circuit board!

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cosmotic
One thing I started to worry about and which wasn't addressed is that the
technique of wrapping the cable around the power line hinders power line
repair or could preclude future applications like this. Can the same robot
traverse the same line with the cable already applied? Can a second cable be
applied over the first?

~~~
londons_explore
the actual lines themselves tend to not really have any repair - nobody sees
one strand of a 50 strand cable looking a bit frayed and replaces it...

You just replace the whole cable at its end-of-life.

~~~
delfinom
Hah, I've never seen a utility schedule end of life for cables. They just
replace them as they break, they'll replace chunks if the cable itself is
looking bad, but otherwise they'll just splice it together with a coupler.

If fiber optic is in the way, they'll just cut it.

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johnbatch
Discussion from two days ago:
[https://news.ycombinator.com/item?id=23825132](https://news.ycombinator.com/item?id=23825132)

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mrep
The fb engineering page has more info [0] and reddit has quite a few comments
from people in the industry about its feasibility [1].

[0]: [https://engineering.fb.com/connectivity/aerial-fiber-
deploym...](https://engineering.fb.com/connectivity/aerial-fiber-deployment/)

[1]:
[https://old.reddit.com/r/EngineeringPorn/comments/hrb6xv/rob...](https://old.reddit.com/r/EngineeringPorn/comments/hrb6xv/robot_for_deploying_aerial_fiber_internet_that/)

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lykr0n
My first through is why is Facebook doing this? Why do they have a division
that's developing Robotics?

Promising though. Much of the cost of running cable is having someone mount
the cable, drive 30 feet down the road, and mount the cable. Over and Over. If
they can slash the cost of last mile, that's big.

~~~
cosmotic
I suspect more people on the internet means more people on Facebook, means
more ad money.

~~~
Nextgrid
More data as well, considering they can use browsing data from the internet
connection itself to influence ad targeting even when browsing non-Facebook
properties.

------
MisterTea
Without getting into a lot of detail I don't see this being very useful. First
off it only works on wires suspended via pin or post insulators on cross arms.
There are plenty of other suspension methods used for MV distribution so good
luck accommodating them. Most runs are normally interrupted by strain
insulator sets on poles containing switch gear or poles that make sharp turns.
It also needs to accommodate a wide variety of insulator designs which have
varied over the years. Some are tall and narrow, some are short and mushroom
shaped. Some have clamps at the top, some are tied with wire.

Any intervention with the robot also requires a highly trained and certified
linesman crew to manipulate the thing on a live conductor with a potential
upward of 34.5kV line to line. So if the robot gets stuck or breaks down you
need a trained crew to handle it. And how easy is it to repair a broken fiber
on a downed power line?

This looks like another solar roadways.

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orev
Interesting idea, but I don’t see any mention on how they deal with the power
line stretching. As power draw goes up, the electric company pumps more juice,
which heats up the cable and in summer months it gets so hot (everyone using
A/C), that the wires start to stretch and sag. The fiber would need to deal
with that.

~~~
HPsquared
I don't think overhead power lines heat up much in normal operation, given the
economics involved. They will definitely expand/contact in line with ambient
conditions however, and also must be flexible enough to sway in the wind
without causing excessive abrasion between the cable and fibre. Edit: the
helical wrap would probably expand/contact more than the electrical cable, as
it'd be "wider" overall.

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fyfy18
The article mentions the main costs with deploying fibre "lie within the
construction of new poles and other infrastructure". Is there any reason why
fibre can't be strung between existing power poles? They aren't conductive, so
you don't need to worry about distances to buildings (i.e. they could be run
lower than power lines).

~~~
MisterTea
The costs involved have to do with labor needed to string cables. You need a
crew of humans in bucket trucks moving from one set of poles to the next.
Whereas this robot clamps to the conductor which acts as a rail and the little
robot can string the fiber on its own for the length of the cable.

~~~
fyfy18
Right that's what I thought. Maybe in North America where labour costs are
high this will be popular, but the article talks about developing countries
where lower labour costs and less regulations make deployment of fibre a lot
cheaper.

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timthorn
A telco was established in the UK by the National Grid during the 1990s using
the high voltage distribution network as the backbone, and wrapping fibre
around the neutral conductor. They called it Energis, and it had a great
slogan at one point: "dial on the pylon"

IIRC after a while they moved to integrating the fibre bundle in the neutral
conductor cable.

~~~
martyvis
In the early 2000s I was on a project that was planning on using the fibre
that was embedded in the neutral conductor in the local grid here in eastern
Australia. It was used for telemetry and power control, but they thought they
could sell access to ISPs and the like. I don't think it ended up going beyond
a few pilot deployments and then our National Broadband Network got the go-
ahead

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erentz
We’ve wrapped fiber around ground wire in the past. Though here they’re doing
it around the conductor. Also their robot is an advancement and pretty cool.
But when I’ve worked in the power industry in the past the guys who had
experimented with this stuff wound up really hating it for the difficulties it
adds to maintenance and the like. So this may be cool but I wouldn’t be
surprised to see it rarely used in actual practice. Strikes me a lot like
project loon and all these other things where people are trying invent
unnecessary shortcuts. If you really want to get internet to people with a
reasonable bandwidth/coverage/and cost trade off start building large towers
dotted across the continent and use wireless access, or wait for star link.

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walrus01
I don't see this being used other than by electrical grid operators
themselves, there's no way they would let third party telecom companies do
this, for grid-reliability and safety reasons.

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elif
I've seen some gnarly utility line webs in south america. There's something
beautiful about the chaos, like a cyberpunk puzzle box for anyone that wants
to get signals from it.

~~~
michaelt
In that case, you might enjoy
[https://powerlinesinanime.tumblr.com/](https://powerlinesinanime.tumblr.com/)

~~~
elif
thank you!!

serial experiment lain has some iconic shots that stick in my memory
[https://powerlinesinanime.tumblr.com/tagged/lain](https://powerlinesinanime.tumblr.com/tagged/lain)

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orbital-decay
How do they pass the more complex transitions between line sections? I vaguely
recall that being a significant limitation of existing line-crawling robots.

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Lexodusk
It's only 1.5km - 2km, and it looks promising, but I wonder how do they splice
it. I was hoping the video would tell, but unfortunately not.

~~~
withinboredom
They probably just attach a junction/amplifier as needed, directly to the
grid.

