Aotearoa Weekly Kōrero 8/7/2024
Aotearoa Weekly Kōrero 8/7/2024
Welcome to this week’s casual kōrero thread!
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The annual fucking of Wellington commuter trains by icy overhead lines has begun. If only there was some kind of power source nearby that could be tapped into and used to deice the lines...
Other options are a deicing spray, like what is used on aircraft, both at airports and in flight, or some type of heater that has a heating element directly on the wire.
Turning an old unit into a deicing train wouldn't be massively difficult, I would think.
I'd love to write the business case for a deicing unit.
I'm wondering about the heating thing. The cables already carry current. Normally for electric heating you'd have electricity going through a wire with high resistance to make the heat. So you'd think you'd run such a wire along the length of the cable. Putting fan heaters everywhere isn't going to be efficient, you need it on the wire in the place it's needed.
But if it's on a live wire, can that work? Or would it just become part of the larger wire and not heat up as the electricity flows through the path of lower resistance? Plus the risk of the pantograph damaging the heating wire.
This is how power line deicing works on systems overseas. You need two legs to the circuit, so it would involve either isolating lines from each other on double track, or earthing out the end of the lines, and using the tracks as a return path.
The option I was actually thinking about was having a heated pantograph of some type.
That's really cool! It sounds like they switch the section to a separate circuit and then pile a carefully controlled high voltage current into it to warm up the line without melting it. But it also says the line remains operational, if I'm reading it right. Not sure how you send too much power through the line without affecting the trains using the line.
Anyway, it sounds like this is the only system like it in the world, and it was installed after heavy snow caused a collapse of much of the network. What I take from that is that it's probably really expensive to install, and probably not worth it in Wellington. One of the ice scraping pantograph options probably makes more sense.
I guess for your heated pantograph option you'd run it on a special de-icer train at low speed? I would think melting the ice off via a pantograph would take a really long time.
The line is out of action while deicing is taking place, but only for the shortest amount of time necessary.
That's what I'm thinking, yes. Although you could pump a lot of heat into the pantograph, and pair it up with a scraper at the same time.
It wouldn't be able to run line speed, but it would be reasonably fast, I'd think.
Ah yes paired with a scaper that would be quite effective. I was thinking you melt it but then the heat is gone and the cable is still frozen so it would refreeze. But if you soften it with the heat then scape it, that could work quite well.
Probably not much chance of getting it implemented in Wellington, though. There might be a slim chance if there was an off the shelf solution, but from my reading into this is seems everything is quite custom.
It's been done with power lines overseas, where they somehow increase the current in the lines to heat them up to shed ice.
No idea how it actually works though, I'll have to look into it.
I guess the question is how to efficiently heat the lines. Not really feasible to install fan heaters all the way along. Heating up the wire itself may not be that easy.
I went looking and found that some solutions are to either use a specially equipped ice cutting diesel engine, or some trains have a separate pantograph (the thing that goes against the wire) that is designed to scrape the ice off just ahead of where the power collecting pantograph is. Some interesting bits in this blog post.
It links through to this page that has photos of the ice cutting pantographs, though not in action.
Oh neat. Unlikely to happen here, I think.