| Author |
Message |
David Lesher
Guest
|
 Posted:
Mon Jun 13, 2005 12:33 pm Post subject:
Hoover Dam Power cable and skin effect |
|
|
So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
1) It's been a while, but the only think I could recall was skin effect,
and my remaining feeble brane tells me was nil until the UHF region.
2) It's built out of a number (~8) of flat pieces with tongue and groove
edges, interlocked and twisted. I'm still pondering how they made it...
3) While looking, I found:
<http://www.ieee.org/organizations/history_center/oral_histories/transcripts/c-smith.html>
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
|
|
| Back to top |
|
 |
Fred Bloggs
Guest
|
| Posted:
Mon Jun 13, 2005 4:35 pm Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
| Quote: | So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
|
An insulating fluid or gas filled the line. From
http://encarta.msn.com/sidebar_461501187/1939_Electrical_Engineering.html
Transmission and Distribution.
Work on the first phase of the Ross Dam on the Skagit River by the City
Lighting Department of Seattle, Washington, is now being completed.
There are ultimately to be three dams, developing a total of 1,120,000
horsepower. The Ross Dam is farthest upstream of the three and will be
655 ft. over all. The cost of this particular development is $5,600,000,
45 per cent of which is PWA funds; the ultimate output will be 360,000
kw. The two lower plants will have a capacity of 240,000 kw. each. This
dam will create a 3,000,000 acre-foot reservoir, equivalent to 600 days'
flow of the river, giving complete storage for power and flood control.
The construction of the third 287,000-volt, three-phase line from
Boulder Dam to Los Angeles is now under way, assuring an added source of
power to the Pacific Coast. The line conductors are the General Cable's
1.4-inch, type-HH, hollow conductor built up of ten segments to form a
smooth copper tube.
High-voltage underground cables have hitherto been insulated with paper
tapes, wound spirally about the conductor and impregnated with either
heavy mineral oils (called the solid type) or a light viscous oil that
flows in and out through the hollow core to a sylphon or accordion-like
drum, with contraction and expansion (called the oil-filled type). Such
cables are, of course, enclosed in a lead sheath. A new development is
the gas-filled cable. The bulk of the oil is drained from the paper, and
the cable is filled with an inert gas at 10 pound pressure. Although
this cable does not have the life of the oil-filled type, nevertheless
it has a longer life than the solid type, and the cost is much less than
that of the oil-filled type. |
|
| Back to top |
|
|
Tim Wescott
Guest
|
| Posted:
Mon Jun 13, 2005 9:32 pm Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
David Lesher wrote:
| Quote: | So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
1) It's been a while, but the only think I could recall was skin effect,
and my remaining feeble brane tells me was nil until the UHF region.
2) It's built out of a number (~8) of flat pieces with tongue and groove
edges, interlocked and twisted. I'm still pondering how they made it...
3) While looking, I found:
http://www.ieee.org/organizations/history_center/oral_histories/transcripts/c-smith.html
|
The skin effect has a depth proportional to frequency and (IIRC)
inversely proportinal to conductance. It causes problems with small
wires at frequencies as a few hundred kHz -- this is why
high-performance coils for 455kHz IF transformers are wound with litz
wire, as well as a few high-frequency switcher coils that I've seen.
Above a couple of MHz even the conductors in litz wire are too big, so
you just don't bother any more.
Search around a bit and you'll find literature on the skin effect on the
web -- given the 1" depth of the conductors you have, and my dim
recollections from E&M theory in school I think you'll find it's on the
order of 1/2" for copper at 60Hz.
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
|
|
| Back to top |
|
|
Jim Thompson
Guest
|
| Posted:
Mon Jun 13, 2005 9:47 pm Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
On Mon, 13 Jun 2005 09:32:14 -0700, Tim Wescott <tim@seemywebsite.com>
wrote:
| Quote: | David Lesher wrote:
So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
1) It's been a while, but the only think I could recall was skin effect,
and my remaining feeble brane tells me was nil until the UHF region.
2) It's built out of a number (~8) of flat pieces with tongue and groove
edges, interlocked and twisted. I'm still pondering how they made it...
3) While looking, I found:
http://www.ieee.org/organizations/history_center/oral_histories/transcripts/c-smith.html
The skin effect has a depth proportional to frequency and (IIRC)
inversely proportinal to conductance. It causes problems with small
wires at frequencies as a few hundred kHz -- this is why
high-performance coils for 455kHz IF transformers are wound with litz
wire, as well as a few high-frequency switcher coils that I've seen.
Above a couple of MHz even the conductors in litz wire are too big, so
you just don't bother any more.
Search around a bit and you'll find literature on the skin effect on the
web -- given the 1" depth of the conductors you have, and my dim
recollections from E&M theory in school I think you'll find it's on the
order of 1/2" for copper at 60Hz.
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
|
For copper it is about 0.85cm (or about 1/3") at 60Hz.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food. |
|
| Back to top |
|
|
Tim Shoppa
Guest
|
| Posted:
Mon Jun 13, 2005 10:10 pm Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
| Quote: | the cable is filled with an inert gas at 10 pound pressure
|
What do they actually use? Nitrogen? Sulfur Hexafluroide? I'm
guessing since they were talking about 287000 volts maybe it is SF6.
Tim. |
|
| Back to top |
|
|
Glen Walpert
Guest
|
| Posted:
Tue Jun 14, 2005 12:36 am Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
On Mon, 13 Jun 2005 13:11:44 GMT, Fred Bloggs <nospam@nospam.com>
wrote:
| Quote: |
So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
An insulating fluid or gas filled the line. From
http://encarta.msn.com/sidebar_461501187/1939_Electrical_Engineering.html
Transmission and Distribution.
Work on the first phase of the Ross Dam on the Skagit River by the City
Lighting Department of Seattle, Washington, is now being completed.
There are ultimately to be three dams, developing a total of 1,120,000
horsepower. The Ross Dam is farthest upstream of the three and will be
655 ft. over all. The cost of this particular development is $5,600,000,
45 per cent of which is PWA funds; the ultimate output will be 360,000
kw. The two lower plants will have a capacity of 240,000 kw. each. This
dam will create a 3,000,000 acre-foot reservoir, equivalent to 600 days'
flow of the river, giving complete storage for power and flood control.
The construction of the third 287,000-volt, three-phase line from
Boulder Dam to Los Angeles is now under way, assuring an added source of
power to the Pacific Coast. The line conductors are the General Cable's
1.4-inch, type-HH, hollow conductor built up of ten segments to form a
smooth copper tube.
High-voltage underground cables have hitherto been insulated with paper
tapes, wound spirally about the conductor and impregnated with either
heavy mineral oils (called the solid type) or a light viscous oil that
flows in and out through the hollow core to a sylphon or accordion-like
drum, with contraction and expansion (called the oil-filled type). Such
cables are, of course, enclosed in a lead sheath. A new development is
the gas-filled cable. The bulk of the oil is drained from the paper, and
the cable is filled with an inert gas at 10 pound pressure. Although
this cable does not have the life of the oil-filled type, nevertheless
it has a longer life than the solid type, and the cost is much less than
that of the oil-filled type.
|
Interesting cable types, however insulated HV cables like that are
only used underground or in short runs in wireway due to cost and
weight. HV distribution cable on towers is uninsulated. AFIK the
interlocked segmented tube design is standard for HV distribution on
towers because of previously mentioned skin effect and because
friction between the segments helps damp wind-induced wire oscillation
thus reducing stresses on the wire. The center is not filled with
anything except ambient air.
I expect that assembly of the segments is done with something very
closely resembling tubing drawing equipment, with the wire drawn
through and over fixed dies which squeeze the female groove over the
male tounge while squishing the joints tightly. |
|
| Back to top |
|
|
Fred Bloggs
Guest
|
| Posted:
Tue Jun 14, 2005 6:42 am Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
Tim Shoppa wrote:
| Quote: | the cable is filled with an inert gas at 10 pound pressure
What do they actually use? Nitrogen? Sulfur Hexafluroide? I'm
guessing since they were talking about 287000 volts maybe it is SF6.
Tim.
|
I don't know- this would be worthwhile to track down. |
|
| Back to top |
|
|
Fred Bloggs
Guest
|
| Posted:
Tue Jun 14, 2005 6:44 am Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
Glen Walpert wrote:
| Quote: | On Mon, 13 Jun 2005 13:11:44 GMT, Fred Bloggs <nospam@nospam.com
wrote:
So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
An insulating fluid or gas filled the line. From
http://encarta.msn.com/sidebar_461501187/1939_Electrical_Engineering.html
Transmission and Distribution.
Work on the first phase of the Ross Dam on the Skagit River by the City
Lighting Department of Seattle, Washington, is now being completed.
There are ultimately to be three dams, developing a total of 1,120,000
horsepower. The Ross Dam is farthest upstream of the three and will be
655 ft. over all. The cost of this particular development is $5,600,000,
45 per cent of which is PWA funds; the ultimate output will be 360,000
kw. The two lower plants will have a capacity of 240,000 kw. each. This
dam will create a 3,000,000 acre-foot reservoir, equivalent to 600 days'
flow of the river, giving complete storage for power and flood control.
The construction of the third 287,000-volt, three-phase line from
Boulder Dam to Los Angeles is now under way, assuring an added source of
power to the Pacific Coast. The line conductors are the General Cable's
1.4-inch, type-HH, hollow conductor built up of ten segments to form a
smooth copper tube.
High-voltage underground cables have hitherto been insulated with paper
tapes, wound spirally about the conductor and impregnated with either
heavy mineral oils (called the solid type) or a light viscous oil that
flows in and out through the hollow core to a sylphon or accordion-like
drum, with contraction and expansion (called the oil-filled type). Such
cables are, of course, enclosed in a lead sheath. A new development is
the gas-filled cable. The bulk of the oil is drained from the paper, and
the cable is filled with an inert gas at 10 pound pressure. Although
this cable does not have the life of the oil-filled type, nevertheless
it has a longer life than the solid type, and the cost is much less than
that of the oil-filled type.
Interesting cable types, however insulated HV cables like that are
only used underground or in short runs in wireway due to cost and
weight. HV distribution cable on towers is uninsulated. AFIK the
interlocked segmented tube design is standard for HV distribution on
towers because of previously mentioned skin effect and because
friction between the segments helps damp wind-induced wire oscillation
thus reducing stresses on the wire. The center is not filled with
anything except ambient air.
I expect that assembly of the segments is done with something very
closely resembling tubing drawing equipment, with the wire drawn
through and over fixed dies which squeeze the female groove over the
male tounge while squishing the joints tightly.
|
This would be worthwhile tracking down too- a clever means of avoiding
embrittlement of the copper due to constant flexing. |
|
| Back to top |
|
|
Robert Baer
Guest
|
| Posted:
Wed Jun 15, 2005 12:36 am Post subject:
Re: Hoover Dam Power cable and skin effect |
|
|
Fred Bloggs wrote:
| Quote: |
So a friend brought me a souvenir from a trip west.
It's a 3" section of old Dam->LA power cable, surplused when some
of the towers were moved for highway construction.
It's of interesting design... it's ~1" in dia, copper, and hollow.
The NPS brochure has some mumble-jumbo about interacting fields,
etc. making the center pointless.
An insulating fluid or gas filled the line. From
http://encarta.msn.com/sidebar_461501187/1939_Electrical_Engineering.html
Transmission and Distribution.
Work on the first phase of the Ross Dam on the Skagit River by the City
Lighting Department of Seattle, Washington, is now being completed.
There are ultimately to be three dams, developing a total of 1,120,000
horsepower. The Ross Dam is farthest upstream of the three and will be
655 ft. over all. The cost of this particular development is $5,600,000,
45 per cent of which is PWA funds; the ultimate output will be 360,000
kw. The two lower plants will have a capacity of 240,000 kw. each. This
dam will create a 3,000,000 acre-foot reservoir, equivalent to 600 days'
flow of the river, giving complete storage for power and flood control.
The construction of the third 287,000-volt, three-phase line from
Boulder Dam to Los Angeles is now under way, assuring an added source of
power to the Pacific Coast. The line conductors are the General Cable's
1.4-inch, type-HH, hollow conductor built up of ten segments to form a
smooth copper tube.
High-voltage underground cables have hitherto been insulated with paper
tapes, wound spirally about the conductor and impregnated with either
heavy mineral oils (called the solid type) or a light viscous oil that
flows in and out through the hollow core to a sylphon or accordion-like
drum, with contraction and expansion (called the oil-filled type). Such
cables are, of course, enclosed in a lead sheath. A new development is
the gas-filled cable. The bulk of the oil is drained from the paper, and
the cable is filled with an inert gas at 10 pound pressure. Although
this cable does not have the life of the oil-filled type, nevertheless
it has a longer life than the solid type, and the cost is much less than
that of the oil-filled type.
Filling a conductive tube with either gas or fluid cannot help |
"insulate" anything.
However, the filler can help incooling, especially if it flows
(eventually) thru a heat exchanger. |
|
| Back to top |
|
|
ftldny
Joined: 06 Jan 2006
Posts: 1
|
| Posted:
Fri Jan 06, 2006 4:49 am Post subject:
|
|
|
I think earlier posts have misinterpreted this source document:
http://encarta.msn.com/sidebar_461501187/1939_Electrical_Engineering.html
This is a general review of transmission line news from 1939; each paragraph is a separate item. So the Boulder Dam cable (an aerial cable) had nothing to do with the underground cables described.
Here's an image of the cable:
http://waynesword.palomar.edu/lightni3.htm
And some more info:
http://www.h-net.msu.edu/~business/bhcweb/publications/BEHprint/v015/p0029-p0042.pdf
The most significant special fitting Thomas & Betts developed during the Depression was the one for the Boulder Dam to Los Angeles electrical transmission cable. Boulder Dam's electrical facilities involved the design, construction, and operation of works with a larger capacity and a higher voltage than their predecessors. When ultimately completed in 1936, the Department of Water and Power of the city of Los Angeles in conjunction with the Southern California Edison Company operated a 345 kilovolt transmission line. The Department of Water and Power contracted with the General Cable company to supply a brand new, recently approved cable from Germany, "Heterodyne" (commonly called HH) cable, an articulated hollow bronze cable, approximately 1-5/8 inches in diameter. In order to make the cable flexible, it was constructed in segments composed of helically wound, lapped copper strips The Germans however, had been unable to design a workable connector.
General Cable evidently conducted a world-wide search for a firm that could produce one. After the search had been underway for some time, a chief engineer for General Cable, a Princeton roommate of G. C. Thomas, called him (probably sometime in mid-1933) and inquired if Thomas & Betts could design such a fitting. Thomas responded enthusiastically. He, Lewis Church, and Martin Bergen sat down and designed what they felt would be a workable connector. The telephone communications between Los Angeles and Elizabeth became so numerous that the company decided to send Church to Los Angeles during what appeared to be a critical period. MacDonald accompanied Church and recalls that Church phoned Elizabeth every day with work for the engineering department.
After approximately a month's residence in Los Angeles, the city's purchasing agent asked MacDonald how long it would take Thomas & Betts' competitors to bid on the project. He answered it would take them well over a month, if they did the complete engineering job. The purchasing agent then announced his intention to ask for bids in ten days because the Los Angeles engineers concluded the Thomas & Betts connector was what they wanted; they were anxious to get started on the project. Ten days later, Thomas & Betts got the contract without any competition. There were no complaints because no one else was in a position to produce such connectors. The finished product was of such a quality that Thomas & Betts was asked to produce the suspension clamps, jumper taps, dead ends, and other accessories. The connector order amounted to approximately $300,000, the largest order ever placed
with Thomas & Betts to that date.
Martin Bergen commented that in later years he learned there had been minor problems with these transmission lines. Where the lines crossed the California desert, a fine, powdery sand became lodged in the joints between the segments, filling up the inside of the connectors, adding sufficient weight to cause the line to break. In 1985, a fifty-year anniversary celebration of the transmission line was held and many of the original connectors were still in use. |
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in
