Comment by unwind | Hacker News Reader

Comment by unwind | Hacker News Reader

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Since it says that the biggest threat against the electrical supply system is trees, shouldn't it be possible to design a drone-based automatic transmission line inspection system?

I mean "just" have a drone with appropriate sensors fly the length of the lines, looking for tree branches that are threatening. Perhaps using machine vision, or something simpler like lidar/radar/ultrasonics/whatever. Signal human inspectors when something looks fishy enough, with video attached for quick review/triage.

Optimally designed to allow recharging the drone's batteries somehow from the top of the pylons (aren't there electrical fields that might be used somehow[1]?), to allow extended automated runs.

Obviously covered in rubber or something to make the chance of damaging the infrastructure in case of a crash minimal.

Crazy?

[1] No idea if this is possible but it would be super neat since it might allow it to scale to run on hundreds of miles of power lines without many humans and with good coverage.

See the "Deep Intelligence" section in this MS Ignite blog post. Lots of companies out there doing this, just a google search away:

https://blogs.technet.microsoft.com/machinelearning/2016/10/...

There are several vendors that do something similar with robotic inspections of underground pipes.

A robot is able to inspect (map and video) a 6" pipe better than a human can!

I knew someone who used to work at a place that built those bots for natural gas lines. Really interesting stuff. They nicknamed them pigs, if I recall.

You recall correctly:

https://en.wikipedia.org/wiki/Pigging

I think my introduction to these devices was one of the three Bond films they mention in the article, probably Diamonds are Forever.

Why not spend the money to bury the transmission lines? At least the small ones.

As http://www.cnn.com/2014/02/12/us/winter-storm-power-lines/ explains:

"underground power lines cost five to 10 times more than overhead wires, don't last as long and cost more to replace..."

and

".... underground lines "are not without their disadvantages,... While more reliable 'under normal weather conditions', they take almost 60% longer to fix when something does happen to them."

Wait, underground lines have a shorter life?

> "Buried power lines are protected from the wind, ice and tree damage that are common causes of outages, and so suffer fewer weather or vegetation-related outages," it concluded. "But buried lines are more vulnerable to flooding, and can still fail due to equipment issues or lightning."

Does flooding happen that often that it significantly decreases their life?

I worked on some small pieces of things mentioned in the article, specifically around the maintenance and reliability of the underground network in Manhattan.

There is a mix of submersible transformers and those that can handle water but can't be submersed in the city. The former are usually placed in areas that are prone to flooding, they are much more expensive than a regular transformer since they are basically waterproof and have a number of extra features built into them so they require less maintenance.

In Manhattan proper, the worst enemies of the underground network are salt + water and the build up of gases. Salt and water + eletricity = corrosion which leads to burnouts. There has been a significant move to try and preemptively visit underground vaults and clear them of the salty water after a snow melt.

Most underground cabling is enclosed in an oil filled casing. Over time these wear and leak. Those gases can fill the underground transformer vaults and lead to explosions. These events are usually pretty well documented and again, ConEdison has been putting procedures and inspection routines that help prevent these.

What is amazing about the Manhattan and Brooklyn networks is how resilient they are simply by the simplicity of design. A transformer outage in a certain area can go almost completely unnoticed by citizens because of the control centers around the city and how they will reroute power. It's something that doesn't exist just about anywhere else and allows crews to isolate issues and perform maintenance when needed.

I'm thinking there are two possible reasons why weather could cause an issue for buried lines, especially for lines in upstate New York feeding the city:

First, the cable would have to be buried deep enough where temperature fluctuations are minimal. If the temperature is allowed to fluctuate widely enough, the cable would be subject to expansion/contraction stress and could then fail. Overhead lines wouldn't have this same issue since the catenary shape of the wires allows room for this expansion and contraction -- solid earth doesn't.

Secondly, if it is buried deeply enough where temperature isn't much of a factor and something fails, now you have to dig that much further to get to/repair/replace the wire. Add on top of that the dead of winter and the rural rights of way that these buried lines would likely be under and that's another big mess.

Keep in mind I'm just speculating here. I'm no expert.

Does flooding happen that often...

Every time it rains heavily, the water table rises temporarily, in low-lying areas. It's not a flood, but it swamps things that are underground. If an earthworm would drown, a cracked junction box would leak.

Physics, specifically their much higher capacitance. The buried lines cost more, but mainly they aren't buried because of physics.

"A typical 345,000V transmission line will be able to deliver no power when the line becomes about 26 miles long."

https://www.puc.nh.gov/2008IceStorm/ST&E%20Presentations/NEI...

In New York City specifically most distribution (not transmission) is already underground.

http://www.nyc.gov/html/planyc2030/downloads/pdf/power_lines...

Air is a better insulator

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