Spacer Installation on 765,000 volt line

[Homer J Simpson]

[rstofer]

Pretty nice flying!

That process is a lot smoother than I would have imagined.  Utility companies get the best stuff!

[German_EE]

From the ground those spacers look quite small!

[PartialDischarge]

Trick question. Who knows why those spacers are so important??

Clue: Each phase could use a single thicker wire, but it is more convenient to mount 2, 3 or 4 wires per phase

[mikeselectricstuff]

The electrostatic field of the spaced conductors is equivalent to that of a much larger wire, so less corona loss.
Probably also has some mechanical advantages - less swaying etc.

[PartialDischarge]

Yep, mostly every engineer I know thinks its done to carry more current

[floobydust]

The arc to the chopper (ground) is fairly big when he unhooks the lead 02:54

When I worked in the industry, we would de-energize a line and connect ground chains before doing any work.
Even pF's of stray capacitance, lethal and violent at these voltages.

[rstofer]

Those wires were probably grounded.  The helicopter is generating the static electricity.  That's one of the issues with rescues at sea.  Never touch the winch cable until after it has been grounded.

[mikeselectricstuff]

Those wires were probably grounded.  The helicopter is generating the static electricity.  That's one of the issues with rescues at sea.  Never touch the winch cable until after it has been grounded.

No it's live - those were clearly AC arcs. Static would just be a single spark.

[theleakydiode]

The arc to the chopper (ground) is fairly big when he unhooks the lead 02:54

When I worked in the industry, we would de-energize a line and connect ground chains before doing any work.
Even pF's of stray capacitance, lethal and violent at these voltages.

But doesn't that create power outages/downtime?

[NiHaoMike]

The arc to the chopper (ground) is fairly big when he unhooks the lead 02:54

When I worked in the industry, we would de-energize a line and connect ground chains before doing any work.
Even pF's of stray capacitance, lethal and violent at these voltages.

But doesn't that create power outages/downtime?

Single points of failure are exactly what grids are designed to not have. When they take down a line or other device for maintenance, it is usually part of a redundant system so there would only be a loss of capacity.

[Brumby]

Those wires were probably grounded.  The helicopter is generating the static electricity.  That's one of the issues with rescues at sea.  Never touch the winch cable until after it has been grounded.

No it's live - those were clearly AC arcs. Static would just be a single spark.

Exactly.

Those lines are very much live.  Grounding - or getting anywhere near a grounded point would be catastrophic!!

They do live works as well. As long the chopper has the same potential as the cable, there's nothing to worry about.

That is why it is safe.

The capacitive current is lethal, but not a big deal for the chopper. The workers have metal shielded cloths so a few tens or hundreds of mAs through their body isn't a big deal either.

Hence why the initial approach is done with a wand.  It takes the first arc strikes and then contact is made.  At that point, the helicopter and everything on board is at the live voltage - with a bit of leakage to the atmosphere.  While the wand is still in contact with the power lines, a hook is attached which ensures this contact is maintained during the process.

The work is then done.  The hook is then removed - making sure the wand is still in contact with the lines and then the helicopter backs off, with the wand being the last thing to break contact from the power lines.  The arcs then reappear until the helicopter is far enough away for them to cease.

If you follow the process correctly, it is quite safe.  Your biggest risk is wind gusts on the helicopter.

[floobydust]

You have to be able to take a power line out of service, for repairs. Usually you will see a double-circuit; another 3-phase set on the same or adjacent power poles.

In this video does not look like a 765kV line? the insulators and clearances look small to me. Here we have 500kVDC lines with 16m spacing, and shield wires.

4-1590 MCM ACSR per pole is probably close to a GW for this transmission line!

[Red Squirrel]

That looks fun.

I think those are live, they use a helicopter because that way there's no path to ground so it's safe for same reason birds can land on HV lines.

I always figured the spacers were just so the cables don't keep rubbing against each other causing wear and tear. 

[CatalinaWOW]

Running two lines with spacers lowers capacitance/unit length.  Eases power factor correction on long lines among other things.

[jordanp123]

Looks like wood tower is holding the lines up. We have one of AEP's 765KV lines in my neck of the woods and with my job I end up being near quite a few of them, all the ones  I've ever seen are metal. Not saying that it can't be, just pointing it out.

[calexanian]

Cool. Never seen it from that perspective.

[TerraHertz]

Yep, mostly every engineer I know thinks its done to carry more current

Well, I knew it was to minimize corona.
Next question: why do those new spacer units have black plastic insulator inner sleeves, isolating the frame from the wires?
I can think of three reasons, but not sure if they are all significant.

In this video does not look like a 765kV line? the insulators and clearances look small to me. Here we have 500kVDC lines with 16m spacing, and shield wires.

Yeah, it can't be 765KV, the arc start length is way too short. How about 220 or 330KV? Or even less.

[EEVblog]

How close are those blades to the wires 

[TerraHertz]

How close are those blades to the wires 

A couple of meters. Not a windy day activity. And I hope they get huge danger money.

[EEVblog]

How close are those blades to the wires 

A couple of meters. Not a windy day activity.

I'm sure they have very strict wind monitoring and safety limits.

[jordanp123]

This is the structures I normally see with the very large insulators and the double design.

[ludzinc]

The arc to the chopper (ground) is fairly big when he unhooks the lead 02:54

When I worked in the industry, we would de-energize a line and connect ground chains before doing any work.
Even pF's of stray capacitance, lethal and violent at these voltages.

But doesn't that create power outages/downtime?

Single points of failure are exactly what grids are designed to not have. When they take down a line or other device for maintenance, it is usually part of a redundant system so there would only be a loss of capacity.

Let me introduce you to South Australia, with a single interconnector between us and Victoria ...

[chickenHeadKnob]

How close are those blades to the wires 

Close, but the pilot is hyper focused on the separation. You can see that helicopter was also equipped with a wire strike protection system (WSPS). See here:http://magellan.aero/product/wsps/. But that only works when the copter is in forward flight has some momentum and the cable is not too thick. Invented by a company from my home town called Bristol Aerospace -now Magellan.

There is a story behind it, the promo video that is in the link suggests it was due to a request from the Canadian Armed Forces, but I remember it differently and probably incorrectly.  At that time my father was working up in north for Manitoba Hydro.  He had a secretary who was out berry picking and topless on one of her days off during the short summer.  Up in northern Manitoba once you got a few kilometres out of the town of 1000 peeps it was sheer desolation in every direction. She chose to pick under the transmission line right of way as that was accessible by car and had open ground with lots of berries and no muskeg/swamp. Another critical detail: she had enormous natural breasts.

Well as luck would have it a regular line inspection flight of hydro employees (2) and pilot in a rented Bell jet ranger passed overhead spotted her and decided to come back for a second look. The pilot clipped the top lightning arrestor wire and flipped with all fatals. I always thought Bristol was prompted by that accident to invent the WSPS. When they had the local unveiling the first airframe type certified was the Bell jet ranger commercial type. The canadian armed forces also operated that type as the Kiowa so maybe it really was them that asked for it .

[NiHaoMike]

Nowadays, wouldn't it make a lot of sense to use drones for inspection?