I have watched them cleaning and maintaining power lines from helicopters. There is a main line that crosses the San Francisco Bay adjacent to the San Mateo Bridge. Watching helicopters ferry workers onto and off of the HV towers is up there in daredevil land. Especially knowing its all live at 750 KV. All this in clear view of the 100,000 cars per day on the bridge. It can be very distracting. A phase to phase short would be catastrophic.
No, it is not enough. It doesn't matter how much.
Yo, pilot...get close enough that I can hold this stick out, draw a ten foot arc to the helicopter via a grounding conductor tied to the frame, then clamp the wire to the power line while you hold still, get close and let me off...all the while, holding my beer..
Trust me, it'll woik..did the math...
j
Ever notice those big barrels seen near HV switching - they are air tanks..... they are under high pressure to blow the switch contacts open as fast as possible to prevent damage from the arc .... air blast breakers.
I was responsible for all power for fusion energy program at LLNL and that included the HV switch yard maintenance over-sight which took HV directly from the lines from Hoover Dam (at Altamont Pass)... tap'ed them for our Fusion energy program. The arc flash upon opening the HV lines was so intense we were not allowed to look at the flash or would be blinding as we were only about 20-30 feet below the switch. These lines went to two huge transformers to step down the voltage.... the sec circuit breakers were on roll-out train rails and weight about 500 pounds each. Everything to do with high energy power is massive and extremely dangerous to work around and upon. It is impressive to watch servicing on these big HV systems.
Was a lot of fun though....
-RNM
I was responsible for all power for fusion energy program at LLNL and that included the HV switch yard maintenance over-sight which took HV directly from the lines from Hoover Dam (at Altamont Pass)... tap'ed them for our Fusion energy program. The arc flash upon opening the HV lines was so intense we were not allowed to look at the flash or would be blinding as we were only about 20-30 feet below the switch. These lines went to two huge transformers to step down the voltage.... the sec circuit breakers were on roll-out train rails and weight about 500 pounds each. Everything to do with high energy power is massive and extremely dangerous to work around and upon. It is impressive to watch servicing on these big HV systems.
Was a lot of fun though....
-RNM
Last edited:
John, I can’t see the beer bottle
https://www.youtube.com/watch?v=oBJyyEAw-6g
https://www.youtube.com/watch?v=PKXPeTvmVQg
https://www.youtube.com/watch?v=PXiOQCRiSp0
George
Stranded RG-59? We used to use miles of the stuff in my business, it was the default cable. Either Belden, Canare or Gepco. As singles or in 3 wire 5 wire and 6 wire snakes.
Like this.
http://www.belden.com/techdatas/metric/1505F.pdf
These days we've had to go to solid center conductor RG-6, because HD-SDI video won't go far over flexible RG-59 or flexible RG-6. The solid conductor cable is a royal PITA, because it's so hard to coil and uncoil.
Like this.
http://www.belden.com/techdatas/metric/1505F.pdf
These days we've had to go to solid center conductor RG-6, because HD-SDI video won't go far over flexible RG-59 or flexible RG-6. The solid conductor cable is a royal PITA, because it's so hard to coil and uncoil.
Did LLNL ever have sandwich related problems?
https://cds.cern.ch/journal/CERNBulletin/2009/47/News Articles/1221806
*yes correlation not causality yet again.
https://cds.cern.ch/journal/CERNBulletin/2009/47/News Articles/1221806
. *
*yes correlation not causality yet again.
George, thanks again.
I marvel at the skill of the helicopter pilots, surely modern drones could be a sensible replacement.
I have seen a 3m high Tesla coil operating, that arc puts it to shame.
Dan.
Way too creepy, the beer comes after.
I marvel at the skill of the helicopter pilots, surely modern drones could be a sensible replacement.
That high power stuff is still way too creepy.
Creepy but spectacular.
I have seen a 3m high Tesla coil operating, that arc puts it to shame.
Dan.
No but i did find a dead cat stretched between 3000A/480V/3Ph and the transformer shell once. Looked like it thought about jumping from transformer to wire. It was stiff as a board...... caused the CB to trip so we had to find the cause. Shorted cat.
Bread crumbs would not do it. Rain on the insulators have a much larger effect and dont cause power outage.
-RNM
We had a snake event in a house in rural France a couple of years back. A snake got into the outside meter box which had a 3 phase termination. Snake was carbonised but that left a phase short that overvolted everything in the house... Bulbs made a funny noise then went phut, fluorescent lights made some nasty noises, lots of stuff expired.. TV, heating controllers. A nightmare!
AFAIK, it doesn't have the bandwidth of RG6. Stiffer, too I think.
The industry standard is Belden 1694A.
http://www.belden.com/techdatas/english/1694A.pdf
It seems to be what everyone in the entertainment sector likes for HD-SDI. I've also used Gepco R6 snakes with good results. If you need to get 4 or five different signals up into the truss, snakes are the way to go.
RG400 is nice cable to work with it has good frequency response and is double shielded with silver over copper and stranded center and meets mil 17. Cost is $2.85 a foot at aircraft spruce. The ends I use are a crimp on with a ratchet tool. A little stiff but not bad.
Looks interesting, but 50 ohms and too stiff for show biz use. Nice for antenna use, I suppose. Think I've seen something like it for wireless mic antennas.
We use RG11 for drop cable in our plants up to a bandwidth of just over 1GHz.
It's a larger cable than RG6 with less attenuation per foot/meter. 18 AWG center conductor.
The connector is bit different though. They are pin type to reduce the gauge back too F series size otherwise the 18 AWG would never fit.
It would be a lot bulkier snake though but you could go further.
Thanks Dave, worth looking into. When we need to go long distances, or even medium distances with 4K video, we usually go to fiber. It's a pain in the butt, but it goes a long way and is super light and flexible. I can throw a 300' fiber snake into my suitcase and think nothing of it. I do like that. 🙂
That's for RF though. Sine in nature. It might be different for raw video. Surely the capacitance of the cable will take some edge off a fast slewing signal.
Optical at a much higher conversion cost.
- Status
- Not open for further replies.