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OT ...one for the sparkies
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OT ...one for the sparkies
On 28 Jan, 00:14, "mark" wrote:
http://www.glumbert.com/media/highpower Some oddities here - I'm not sure he really knows what a Faraday cage is. But that aside, since the helicopter gets brought to the same potential as the power lines, I presume this is high voltage DC transmission. I wonder where it is? Ian |
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On Mon, 28 Jan 2008 00:14:04 -0000, "mark"
wrote: http://www.glumbert.com/media/highpower _sort_ of d-i-y, innit... -- Frank Erskine |
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In message , mark
writes http://www.glumbert.com/media/highpower mark Yeah, it's been posted several times over the past couple of years -- geoff |
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In message
, The Real Doctor writes On 28 Jan, 00:14, "mark" wrote: http://www.glumbert.com/media/highpower Some oddities here - I'm not sure he really knows what a Faraday cage is. But that aside, since the helicopter gets brought to the same potential as the power lines, I presume this is high voltage DC transmission. I wonder where it is? Canada IIRC -- geoff |
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geoff wrote:
transmission. I wonder where it is? Canada IIRC Got a US flag on his shoulder... could be the Massachusetts end of the line from Ayer in the US to Quebec: http://en.wikipedia.org/wiki/Quebec_...d_Transmission -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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On Jan 28, 3:49*am, geoff wrote:
In message , mark writes http://www.glumbert.com/media/highpower mark Yeah, it's been posted several times over the past couple of years -- geoff Doubt if it is DC. Most transmission lines in NA are AC as far as I know, especially since the Canada-US systems are intertwined and share power on linked grids. This is the scheme where a helicopter borne worker first hooks on then transfers himself to the live transmission wire in order to work on the connections, separators, insulators etc.? Thre is some talk of transmitting electrical power from the proposed Lower Churchill generating site in Newfoundland, Labrador across to the island portion of that province, then some 80 miles across the Gulf of St. Lawrence to Nova Scotia, New Brunswick and New York State. Due to the long underwater link would think DC would be used there; with converters at each end. By the way. In that vein (DC underwater cables); anybody know the answer to this question .....? "There was or is a DC power cable across the north of the North Sea beween Scotland and Norway????" Purpose of which to share power between those two countries which have hydro generating capabilities. Seem to remember reading about it in the mid 1950s. |
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snip
"There was or is a DC power cable across the north of the North Sea beween Scotland and Norway????" Purpose of which to share power between those two countries which have hydro generating capabilities. Seem to remember reading about it in the mid 1950s. ISTR the cross-channel link to France was the announced as the first UK-Europe power sharing. And that seems to be confirmed by a quick Google which brings up the history here with no mention of Scotland until 2001 to NI http://www2.theiet.org/oncomms/secto...53EE3D46B2112D -- Robin |
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neverwas wrote:
snip "There was or is a DC power cable across the north of the North Sea beween Scotland and Norway????" Purpose of which to share power between those two countries which have hydro generating capabilities. Seem to remember reading about it in the mid 1950s. No way. ISTR the cross-channel link to France was the announced as the first UK-Europe power sharing. And that seems to be confirmed by a quick Google which brings up the history here with no mention of Scotland until 2001 to NI http://www2.theiet.org/oncomms/secto...53EE3D46B2112D Yes. I visited it in the 60's and it was as far as I know the ONLY external grid link in the UK at that time, and as far as I know still is. Things that stand out from the visit. - a room, a very large room FULL of thyratron valves ..each one about 8 foot tall. - about 6 acres of capacitors to smooth the output. - Some inductors the size of houses for the same purpose.. - "we can draw a 30KV arc off the line for several hours after switchoff" from the engineer showing us round. A technical marvel, and JUST ABOUT worth it economically. I found a couple of references to linking the Orkney and Shetlands using undersea cables (under consideration): Currently the largest is IIRC in the USA ad is 65m long. National grid had(has?)plans to do a half a billion quid one of a gigawatt capacity to Holland. That is the same order of cost as a half gigawatt power station.. Cost are somewhere near a million quid a mile. More for larger power levels like the above. No references to any scotland- Morway links tho. |
OT ...one for the sparkies
In message , mark
writes http://www.glumbert.com/media/highpower Am I the only person who thinks that's clearly CGI ? -- Si |
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Si wrote:
In message , mark writes http://www.glumbert.com/media/highpower Am I the only person who thinks that's clearly CGI ? I think its for real, but whether the cables are on, and whether you can do more than make a cursory inspection, if they are , is a moot point. The arc drawn looks clearly DC...sort of what might be left on a 132KV line if the contactors flipped out. |
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On Mon, 28 Jan 2008 14:23:38 +0000, The Natural Philosopher wrote:
Si wrote: In message , mark writes http://www.glumbert.com/media/highpower Am I the only person who thinks that's clearly CGI ? I think its for real, but whether the cables are on, and whether you can do more than make a cursory inspection, if they are , is a moot point. The arc drawn looks clearly DC...sort of what might be left on a 132KV line if the contactors flipped out. Just for reference... http://www.youtube.com/watch?v=PXiOQCRiSp0 |
OT ...one for the sparkies
The Natural Philosopher wrote:
I think its for real, but whether the cables are on, and whether you can do more than make a cursory inspection, if they are , is a moot point. I am sure it is real the circuit is not complete (no earth) so NO current will flow. seem to remember watching a documentary about this (the "linesman" stayed on the helicopter platform though) it was "just" an inspection but there seemed to be no fear of touching the wires. C.F. Birds CAN sit on power lines without getting zapped (or there would be lots of dead bird bodies under power lines) but the difference in voltage gives them a slight tingle which they don't like so they tend not to perch on power lines. The arc drawn looks clearly DC...sort of what might be left on a 132KV line if the contactors flipped out. Isn't the arc caused by current flow from the helicopter ? Helicopters can work up a fearsome static PD hence the guys that attach loads to military helicopters touch the load strop with a grounded pole first. In a SAR situation allow the winchman to touch the ground/sea first do not try to grab him (he will probably have some sort of "earthing wire" running through his harness). If your life depends on it grab the strop or WHY and take the belt, it is non lethal it just can be very painful A thread that talks about helicopter static build up:- http://preview.tinyurl.com/32u6gq |
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PCPaul wrote:
On Mon, 28 Jan 2008 14:23:38 +0000, The Natural Philosopher wrote: Si wrote: In message , mark writes http://www.glumbert.com/media/highpower Am I the only person who thinks that's clearly CGI ? I think its for real, but whether the cables are on, and whether you can do more than make a cursory inspection, if they are , is a moot point. The arc drawn looks clearly DC...sort of what might be left on a 132KV line if the contactors flipped out. Just for reference... http://www.youtube.com/watch?v=PXiOQCRiSp0 Thiose isolators are NEVER opened under load though. They have oil filled contactors to actually break the circuits. Those are isolators..thats just redsidual cable capaitance being broken. |
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soup wrote:
The Natural Philosopher wrote: I think its for real, but whether the cables are on, and whether you can do more than make a cursory inspection, if they are , is a moot point. I am sure it is real the circuit is not complete (no earth) so NO current will flow. seem to remember watching a documentary about this (the "linesman" stayed on the helicopter platform though) it was "just" an inspection but there seemed to be no fear of touching the wires. C.F. Birds CAN sit on power lines without getting zapped (or there would be lots of dead bird bodies under power lines) but the difference in voltage gives them a slight tingle which they don't like so they tend not to perch on power lines. The arc drawn looks clearly DC...sort of what might be left on a 132KV line if the contactors flipped out. Isn't the arc caused by current flow from the helicopter ? Helicopters can work up a fearsome static PD hence the guys that attach loads to military helicopters touch the load strop with a grounded pole first. In a SAR situation allow the winchman to touch the ground/sea first do not try to grab him (he will probably have some sort of "earthing wire" running through his harness). If your life depends on it grab the strop or WHY and take the belt, it is non lethal it just can be very painful A thread that talks about helicopter static build up:- http://preview.tinyurl.com/32u6gq Yes, but those cables are NOT running at full AC. Its static off disconnected cables and the chopper you are seeing. AFAIAW teh sequenc to service cable is - blow the contactors. These are ****ING great switches in tanks of inert oil designed to quench sparks. - open up the isolators - drawing a bit of an arc as you do, depending on leakages. - go to section of line and throw an earth strap over it to get rid of static and KEEP it that way. Once isolated it can pick up a lot of static. - THEN put a man on it. |
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I reckon it's AC.
After he's clipped on and climbed onto the wire, he pulls the clip off and the chopper flies off. How could it *not* be at line voltage after being clipped on? OTOH, if the line was running AC at an appreciable voltage you'd need a current flow to charge/discharge the helicopter-capacitor with each cycle. The arc on departure runs to a couple of feet. IIRC 1000V per inch - so the line is at 24kV plus. I can't say *how* much plus, the chopper isn't earthed very well... Andy |
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The Natural Philosopher wrote:
The arc drawn looks clearly DC... You sure? If it were DC the helicopter would just charge up to a constant voltage and the arc would cease - no further charge to transfer, unless there's corona discharge from the rotor tips, or unless it's very ripply DC (unlikely with polyphase rectification). That arc seems fairly sustained, as you'd expect with AC , and a 120 Hz buzzing seems to accompany it. -- Andy |
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In article ,
The Natural Philosopher writes: PCPaul wrote: http://www.youtube.com/watch?v=PXiOQCRiSp0 Thiose isolators are NEVER opened under load though. They have oil filled contactors to actually break the circuits. Those are isolators..thats just redsidual cable capaitance being broken. I saw a detailed write-up of that (and I've got a much better quality video of it). It's a sulphur heaxafluoride (SF6) breaker switch, not oil. The nearest SF6 breaker is half jammed, leaving the isolator as the only means of breaking it. When the SF6 breaker fires, you see the arc flash across the half of the SF6 breaker which does open, because the other half is still jammed closed. That starts the arc across the isolation gap. This switch switches the line inductors in/out at the end of a long transmission line which are correcting for the line capacitance. It's not actually carrying the line current. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
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On Mon, 28 Jan 2008 19:51:36 +0000, The Natural Philosopher wrote:
http://www.youtube.com/watch?v=PXiOQCRiSp0 Thiose isolators are NEVER opened under load though. They have oil filled contactors to actually break the circuits. Those are isolators..thats just redsidual cable capaitance being broken. There is more about that arc if you dig about on the web rather than the few words on yewtube. http://www.arcfault.org/video.htm Fascinating stuff. -- Cheers Dave. pam is missing e-mail |
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On Mon, 28 Jan 2008 21:08:38 +0000,it is alleged that Andy Champ
spake thusly in uk.d-i-y: I reckon it's AC. After he's clipped on and climbed onto the wire, he pulls the clip off and the chopper flies off. How could it *not* be at line voltage after being clipped on? OTOH, if the line was running AC at an appreciable voltage you'd need a current flow to charge/discharge the helicopter-capacitor with each cycle. The arc on departure runs to a couple of feet. IIRC 1000V per inch - so the line is at 24kV plus. I can't say *how* much plus, the chopper isn't earthed very well... Andy Judging by the shot of the long string of cap and pin insulators visible at the end, somewhere in the low hundreds of kV -- _ ( ) ASCII ribbon campaign against html e-mail X and usenet posts / \ |
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On Mon, 28 Jan 2008 00:14:04 -0000, "mark"
wrote: http://www.glumbert.com/media/highpower mark Nothing new there. The UK has been doing something similar for many years. A proof of concept exercise was done by the CEGB in the 1970's and was eventually revived and became normal practice in the early 1990's. They do it from a wheeled trolley though rather than crawling along the line. The discharge you see in the video is completely normal and it's just a case of equalising the charge. The line is fully in service - which is precisely why it is done live, to save the costs of constraining generation, and in the case of operations in the UK could be carrying around 2000A per phase - or 500-1000A per individual conductor Spacer replacement (the H or X shaped bars between individual conductors) on 2 and 4 conductor overhead 400 and 275kV lines is routinely done live in the UK. Last time I saw them in person was two or three years ago on the 400kV line that passes over the A55 near Bangor in North Wales. -- |
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On Mon, 28 Jan 2008 13:28:02 +0000, The Natural Philosopher
wrote: neverwas wrote: snip "There was or is a DC power cable across the north of the North Sea beween Scotland and Norway????" Purpose of which to share power between those two countries which have hydro generating capabilities. Seem to remember reading about it in the mid 1950s. No way. ISTR the cross-channel link to France was the announced as the first UK-Europe power sharing. And that seems to be confirmed by a quick Google which brings up the history here with no mention of Scotland until 2001 to NI http://www2.theiet.org/oncomms/secto...53EE3D46B2112D Yes. I visited it in the 60's and it was as far as I know the ONLY external grid link in the UK at that time, and as far as I know still is. If you visited in the 60's then you visited the old now defunct 160MW link. The new one, rated at 2000MW only entered service in 1986. There is also a link to the Isle of Man built about 6 years ago, one under construction to the Netherlands for completion in 2010, and two others planned to link to Ireland and Norway. -- |
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On Mon, 28 Jan 2008 19:56:13 +0000, The Natural Philosopher
wrote: Yes, but those cables are NOT running at full AC. Oh yes they are. For a start there is no such thing as half AC and more to the point if the lines were out of service then they would always be earthed at the remote ends, with earths placed at the adjacent towers from the conductors to the pylon structure / earthwire and the overhead line worker would approach the conductor by climbing across the insulator strings. In such circumstances you shouldn't ever see discharge and you'd only wear normal clothing rather than a mesh suit. So what you are seeing is not just pickup from an adjacent in service line and in essence that is *exactly* how live line working on HV is performed. -- |
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Matt wrote:
On Mon, 28 Jan 2008 13:28:02 +0000, The Natural Philosopher wrote: neverwas wrote: snip "There was or is a DC power cable across the north of the North Sea beween Scotland and Norway????" Purpose of which to share power between those two countries which have hydro generating capabilities. Seem to remember reading about it in the mid 1950s. No way. ISTR the cross-channel link to France was the announced as the first UK-Europe power sharing. And that seems to be confirmed by a quick Google which brings up the history here with no mention of Scotland until 2001 to NI http://www2.theiet.org/oncomms/secto...53EE3D46B2112D Yes. I visited it in the 60's and it was as far as I know the ONLY external grid link in the UK at that time, and as far as I know still is. If you visited in the 60's then you visited the old now defunct 160MW link. Yup. That was it! The new one, rated at 2000MW only entered service in 1986. 2GW? I suppose solid state switches make it feasible. There is also a link to the Isle of Man built about 6 years ago, one under construction to the Netherlands for completion in 2010, Found that one. and two others planned to link to Ireland and Norway. Norway sounds unlikely..why there? |
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On Tue, 29 Jan 2008 12:01:34 +0000, The Natural Philosopher
wrote: Norway sounds unlikely..why there? Cheap hydro -- |
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Matt wrote:
On Tue, 29 Jan 2008 12:01:34 +0000, The Natural Philosopher wrote: Norway sounds unlikely..why there? Cheap hydro Fairy Nuff. That probably stands on its own two feet then. And the Finns are next door with their reactors... |
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In article , Matt
scribeth thus On Mon, 28 Jan 2008 19:56:13 +0000, The Natural Philosopher wrote: Yes, but those cables are NOT running at full AC. Oh yes they are. For a start there is no such thing as half AC and more to the point if the lines were out of service then they would always be earthed at the remote ends, with earths placed at the adjacent towers from the When they were rewiring the line for Wisbech to Stocking Pelham it seemed they had earths on every pylon!... conductors to the pylon structure / earthwire and the overhead line worker would approach the conductor by climbing across the insulator strings. In such circumstances you shouldn't ever see discharge and you'd only wear normal clothing rather than a mesh suit. So what you are seeing is not just pickup from an adjacent in service line and in essence that is *exactly* how live line working on HV is performed. This is quite a good site on the subject... http://members.tripod.com/~aberkers/work.html -- Tony Sayer |
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On 2008-01-29 13:40:53 +0000, The Natural Philosopher said:
Matt wrote: On Tue, 29 Jan 2008 12:01:34 +0000, The Natural Philosopher wrote: Norway sounds unlikely..why there? Cheap hydro Fairy Nuff. That probably stands on its own two feet then. And the Finns are next door with their reactors... Next door but one unless you go a tortuous way round, |
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We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Matt saying something like: http://www.glumbert.com/media/highpower mark Nothing new there. The UK has been doing something similar for many years. A proof of concept exercise was done by the CEGB in the 1970's and was eventually revived and became normal practice in the early 1990's. Earlier than that. I was told about this in 1970 by a physics lecturer who was ex-industry. Subsequent to that, anytime I saw blokes crawling or trollying around EHV cables I assumed they were doing it live in their mesh suits. -- Dave |
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