Spacer Installation on 765,000 volt line - Page 1
Forum section: electronics / general

author: rstofer
author_rank: Super Contributor
timestamp: March 02, 2018, 04:40:35 pm
content: Pretty nice flying!That process is a lot smoother than I would have imagined. Utility companies get the best stuff!

author: German_EE
author_rank: Super Contributor
timestamp: March 02, 2018, 09:38:47 pm
content: From the ground those spacers look quite small!

author: PartialDischarge
author_rank: Super Contributor
timestamp: March 02, 2018, 10:00:32 pm
content: 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

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 02, 2018, 10:05:28 pm
content: 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.

author: PartialDischarge
author_rank: Super Contributor
timestamp: March 02, 2018, 10:10:53 pm
content: Yep, mostly every engineer I know thinks its done to carry more current

author: floobydust
author_rank: Super Contributor
timestamp: March 02, 2018, 10:41:20 pm
content: The arc to the chopper (ground) is fairly big when he unhooks the lead 02:54When 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.

author: rstofer
author_rank: Super Contributor
timestamp: March 02, 2018, 11:17:15 pm
content: 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 03, 2018, 12:00:14 am
content: Quote from: rstofer on March 02, 2018, 11:17:15 pmNo it's live - those were clearly AC arcs. Static would just be a single spark.

author: theleakydiode
author_rank: Regular Contributor
timestamp: March 03, 2018, 01:09:59 am
content: Quote from: floobydust on March 02, 2018, 10:41:20 pmBut doesn't that create power outages/downtime?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 03, 2018, 01:25:33 am
content: Quote from: theleakydiode on March 03, 2018, 01:09:59 amSingle 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.

author: Brumby
author_rank: Unknown
timestamp: March 03, 2018, 02:10:58 am
content: Quote from: mikeselectricstuff on March 03, 2018, 12:00:14 amExactly.Those lines are very much live. Grounding - or getting anywhereneara grounded point would be catastrophic!!Quote from: blueskull on March 02, 2018, 11:24:49 pmThat is why it is safe.QuoteHence 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.

author: floobydust
author_rank: Super Contributor
timestamp: March 03, 2018, 02:11:21 am
content: 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!

author: Red Squirrel
author_rank: Super Contributor
timestamp: March 03, 2018, 03:12:56 am
content: 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.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 03, 2018, 04:33:30 am
content: Running two lines with spacers lowers capacitance/unit length. Eases power factor correction on long lines among other things.

author: jordanp123
author_rank: Regular Contributor
timestamp: March 04, 2018, 04:02:33 am
content: 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.

author: calexanian
author_rank: Super Contributor
timestamp: March 04, 2018, 04:59:35 am
content: Cool. Never seen it from that perspective.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 04, 2018, 06:38:21 am
content: Quote from: MasterTech on March 02, 2018, 10:10:53 pmWell, 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.Quote from: floobydust on March 03, 2018, 02:11:21 amYeah, it can't be 765KV, the arc start length is way too short. How about 220 or 330KV? Or even less.

author: EEVblog
author_rank: Unknown
timestamp: March 04, 2018, 06:41:03 am
content: How close are those blades to the wires

author: TerraHertz
author_rank: Super Contributor
timestamp: March 04, 2018, 06:43:02 am
content: Quote from: EEVblog on March 04, 2018, 06:41:03 amA couple of meters. Not a windy day activity. And I hope they get huge danger money.

author: EEVblog
author_rank: Unknown
timestamp: March 04, 2018, 06:45:26 am
content: Quote from: TerraHertz on March 04, 2018, 06:43:02 amI'm sure they have very strict wind monitoring and safety limits.

author: jordanp123
author_rank: Regular Contributor
timestamp: March 04, 2018, 07:22:20 am
content: This is the structures I normally see with the very large insulators and the double design.

author: ludzinc
author_rank: Unknown
timestamp: March 04, 2018, 01:58:38 pm
content: Quote from: NiHaoMike on March 03, 2018, 01:25:33 amLet me introduce you to South Australia, with a single interconnector between us and Victoria ...

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: March 05, 2018, 02:43:19 am
content: Quote from: EEVblog on March 04, 2018, 06:41:03 amClose, 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.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 05, 2018, 02:51:03 am
content: Nowadays, wouldn't it make a lot of sense to use drones for inspection?

author: VK5RC
author_rank: Unknown
timestamp: March 05, 2018, 03:01:36 am
content: TerraHertz, re the? plastic, I wonder if it is there for chaffing protection, the operator doesn't appear to be screwing the spacer tightly onto the cables.

author: Brumby
author_rank: Unknown
timestamp: March 05, 2018, 05:13:26 am
content: That was my first thought as well.My second was that the material might be fairly firm and when the clasp was closed - under what looked like significant pressure - that the material deformed around the strands to form a secure, non slipping attachment. By using a material that deformed, you gained a large contact surface area giving very high friction, without deforming/damaging the conductor strands - something a direct fitting metal clasp would do. Any damage to a strand would weaken it - and if it were to fail, then you would have an overall weaker cable ... and the unsecured strand could become a hazard...

author: floobydust
author_rank: Super Contributor
timestamp: March 05, 2018, 05:36:14 am
content: Cable-spacers are used to control galloping, aeolian vibrations, or wake-induced oscillations, from wind and ice on power lines which cause vibration fatigue failures.This is an old pic of 765kV line from Miami, I had no idea they go near the center cable groupvortex pic fromhttp://www.tdee.ulg.ac.be/doc-26.htmlLineman pic by Rick Diaz

author: Gromitt
author_rank: Regular Contributor
timestamp: March 05, 2018, 09:57:25 am
content: https://youtu.be/pjSnKGDna3E?t=28m14s(Sorry, could'nt get it embedded)

author: TerraHertz
author_rank: Super Contributor
timestamp: March 08, 2018, 02:01:28 pm
content: Quote from: Brumby on March 05, 2018, 05:13:26 amThe 3 possibles I thought of:* Mechanical damping. To reduce cable oscillations in wind.* Avoiding metal-to-metal contact, to prevent corrosion and abrasion.* Electrical isolation. Not of the full cable voltage, but of small differential voltages between cable sections. That could be caused by slight cable resistance variations, geomagnetic field variations and so on. Effectively stopping eddy currents. Which could cause more corrosion at the contact points. Also, perhaps such eddy currents could be quite large, cause significant cable temp rise, and thus reduce transmission efficiency?

author: fenugrec
author_rank: Frequent Contributor
timestamp: March 08, 2018, 02:51:20 pm
content: Quote from: NiHaoMike on March 05, 2018, 02:51:03 amDepending on the remoteness, not yet. For slow / stationary flight, you can't beat the range and endurance of a fuel powered machine, which typically means a heli.

author: floobydust
author_rank: Super Contributor
timestamp: March 08, 2018, 08:34:35 pm
content: I booked helicopters at around $1,800/hr + fuel costs, it was about $33/minute.Sharpershapehas drones for the electric utility sector, I think range would too limited especially with IR camera running.