How high is that wire... REALLY?

[thinwater]

Originally Posted by 44'cruisingcat

Ok. That wire, rated at 9 metres is about 40 metres up. So there's about 30 metres for "jump" .

How many volts does that cover?

The spacing suggests 230KV subtransmission lines. The required safety factor on land is about 7 meters. There also appears to be sag to the right. But I don't know the details. Now I'm curious.

[44'cruisingcat]

I doubt they're 230kv! It's power to a small villiage called Bundeena.

The lines get lower, but there's no water under them. The don't get that much lower anyway, maybe down to 30m or so.

Boats with 20m+ masts go under these lines virtually every day.

I think it's a serious/excessive case of CYA.

Re the powerlines in the OP, I wonder if it's a similar case, allowing huge clearance in the worst possible case, which would be when the river is in flood, with levels above the levee banks.

[IslandHopper]

^^^^^^^^^^^^^^^^^^^^

AUGUST 1 2018 - 3:50PM

Ausgrid replaces poles carrying high voltage power lines over Port Hacking

https://www.theleader.com.au/story/5...-risk-removed/

Out of date charts or chart information is my bet.....

Ausgrid has completed the difficult task of replacing poles carrying high voltage power lines over Port Hacking.

The project followed a finding the low height of the power lines presented an “extreme” risk to vessels.

The risk was highlighted by an incident in January, 2011, when the mast of a yacht made contact with the 11,000 volt lines.

Two 36 metre high, steel poles – one at Burraneer and the other at Maianbar – have replaced 22 metre wooden poles.

Crews have completed one of the trickiest stages of major upgrade of overhead powerlines from Burraneer Bay to Maianbar in Sydney's south.

As part of work to raise height of powerlines over Port Hacking River we've replaced 6 shorter poles with 2 taller 35-37m steel poles.

[DougM]

I believe the breakdown voltage for dry air is 3 million volts per metre or so, if i remember correctly. Breakdown voltage increases with humidity i believe, as water vapour has a higher breakdown voltage than air.

Just be careful not to sail under power lines in a vacuum, that could cause long distance arcing

if you want to be conservative, don't get within an insulator length of the line. This distance must be way way longer than an air discharge length. It has to deal with surface effects particularly in humidity and rain, so there is lots of safety factor built in.

[BugzyCan]

A large drone, a piece of string with an open ended hook hanging down, fly over the wire to hook it, lift it up, and sail under. Problem resolved.

[44'cruisingcat]

Originally Posted by IslandHopper

^^^^^^^^^^^^^^^^^^^^

AUGUST 1 2018 - 3:50PM

Ausgrid replaces poles carrying high voltage power lines over Port Hacking

https://www.theleader.com.au/story/5...-risk-removed/

Out of date charts or chart information is my bet.....

Now they need to replace the signs! The warning signs still state 9 metres maximum vessel height.

The steel poles are also mounted on fairly high ground.

[IslandHopper]

Originally Posted by 44'cruisingcat

Now they need to replace the signs! The warning signs still state 9 metres maximum vessel height.

The steel poles are also mounted on fairly high ground.

Yep don't know who that responsibility falls on, maybe your friend can report it....

Australian Hydrographic Office - Contact Information

.....if not them then they will know who....

[Paul L]

The risk was highlighted by an incident in January, 2011, when the mast of a yacht made contact with the 11,000 volt lines.

Anyone know what happen to this boat after making contact?

[Marinegirl405]

Signs ashore say 24m - as of April 2021 at least - :-)

[Jim Cate]

^^^^^
Which wires are those?

Jim

[Marinegirl405]

Originally Posted by Jim Cate

^^^^^
Which wires are those?

Jim

Port Hacking, NSW (Australia) - Overhead power cables between Bundeena to Burraneer Point, were replaced in 2018 - navionics charts still show it as 12m (not updated).

[Uncle Bob]

Originally Posted by Paul L

Anyone know what happen to this boat after making contact?

I believe that insurance fixed the boat, Wild Goose or something like that and then got to fix it again when it "fell over" just off jibbon beach while racing. A somewhat sad sight with one hull up and the mast in the seabed.

[PatB]

Rather than a physical change to the wires, has best practice regarding separation from high voltage conductors been tightened up recently?

[John_Trusty]

Happened in the Keys this month: https://www.miamiherald.com/news/loc...250604514.html

[Jammer]

Originally Posted by John_Trusty

Happened in the Keys this month: https://www.miamiherald.com/news/loc...250604514.html

Looks like they were near the Sunset Grill, a favorite of mine.


https://www.google.com/maps/@24.7064.../data=!3m1!1e3


It appears to me that they were trying to get to the Sunset Grill courtesy dock and somehow didn't see the powerline, which is much higher than the bridge. There's no way they could possibly have been trying to get under the bridge at that point -- it's way too low to clear. There's not much other reason to be in that area.


I see that there is a user-added waypoint in Navionics for the Sunset Grill, that is erroneously placed between the bridge and the powerline. The actual courtesy dock is south of there on the other side of the powerline. Perhaps part of the accident chain.



https://webapp.navionics.com/#boatin...y=y~wuC%60udnN


No sails visible in the photos so they must have been motoring. Or adrift.