B
Bret Cahill
Guest
Is there some low frequency radiation or hysterisis loss or what?
Bret Cahill
Bret Cahill
J
Jan Panteltje
Guest
On a sunny day (Tue, 22 Apr 2008 12:13:06 -0700 (PDT)) it happened Bret Cahill
<BretCahill@aol.com> wrote in
<98d0c415-606a-4d10-8158-1ee67568e4e6@26g2000hsk.googlegroups.com>:
DC can be efficient at very high voltages, where the current is low,
as losses in the wires are i^2.R, but requires big solid state AC/DC and DC/AC
converters at each side.
http://en.wikipedia.org/wiki/Electric_power_transmission
Here is one example where DC is used:
http://en.wikipedia.org/wiki/Pacific_DC_Intertie
<BretCahill@aol.com> wrote in
<98d0c415-606a-4d10-8158-1ee67568e4e6@26g2000hsk.googlegroups.com>:
It all depends, AC has inductive losses, and capacitive losses between lines.
DC can be efficient at very high voltages, where the current is low,
as losses in the wires are i^2.R, but requires big solid state AC/DC and DC/AC
converters at each side.
http://en.wikipedia.org/wiki/Electric_power_transmission
Here is one example where DC is used:
http://en.wikipedia.org/wiki/Pacific_DC_Intertie
D
Don Bowey
Guest
On 4/22/08 12:44 PM, in article
f5cff0ae-802b-4bd4-9e4b-1e16b91ee636@t63g2000hsf.googlegroups.com, "JeffM"
<jeffm_@email.com> wrote:
f5cff0ae-802b-4bd4-9e4b-1e16b91ee636@t63g2000hsf.googlegroups.com, "JeffM"
<jeffm_@email.com> wrote:
Cite where you think he said that. It's not in this thread.
E
Eeyore
Guest
Bret Cahill wrote:
Graham
Where do you get your inital incorrect idea from ?
Graham
J
JeffM
Guest
Bret Cahill wrote:
:10X More Efficient
Cite your sources for 920% efficiency.
:10X More Efficient
Cite your sources for 920% efficiency.
D
Don Bowey
Guest
On 4/22/08 2:32 PM, in article 6773rgF2n665eU1@mid.individual.net, "Phil
Allison" <philallison@tpg.com.au> wrote:
Allison" <philallison@tpg.com.au> wrote:
Gee, thanks phil.
J
John Larkin
Guest
On Tue, 22 Apr 2008 12:13:06 -0700 (PDT), Bret Cahill
<BretCahill@aol.com> wrote:
average voltages (less corona losses, relatively) and has no skin loss
or inductive coupling to the world. I don't know about 10:1.
DC systems do need inverters and rectifiers on the ends, which have
losses.
John
<BretCahill@aol.com> wrote:
If you mean long-distance transmission lines, DC can be run at higher
average voltages (less corona losses, relatively) and has no skin loss
or inductive coupling to the world. I don't know about 10:1.
DC systems do need inverters and rectifiers on the ends, which have
losses.
John
E
Eeyore
Guest
Bret Cahill wrote:
Graham
No they don't.
Graham
B
Benj
Guest
On Apr 22, 5:32 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:
920%! What you must have just graduated from a "modern" high school?
Dig. If standard transmission is 92% efficient, then that means there
is 8% of the energy lost. TWICE as efficient would only have 4% of the
energy lost or would be 96%. The interested student can take it from
there...
Since 10X would be more than 99% efficient I am somewhat skeptical
that even modern converters can produce so little loss.
Are modern "scientists" really this dense? Ten times efficient isn't
920%! What you must have just graduated from a "modern" high school?
Dig. If standard transmission is 92% efficient, then that means there
is 8% of the energy lost. TWICE as efficient would only have 4% of the
energy lost or would be 96%. The interested student can take it from
there...
Since 10X would be more than 99% efficient I am somewhat skeptical
that even modern converters can produce so little loss.
B
Bret Cahill
Guest
Going 10X further with the same 8% loss?
One tenth as lossy for the same distance?
And who mentioned 8%?
Bret Cahill
B
Bret Cahill
Guest
Europeans claim they can run a DC power line from solar thermal fields
in the Sahara thousands of kms to N. Europe.
Bret Cahill
B
Blattus Slafaly ? (3) ź :
Guest
Bret Cahill wrote:
--
Blattus Slafaly ? 3
7/8
Westinghouse's AC prevailed.
--
Blattus Slafaly ? 3
7/8
E
Eric Gisin
Guest
""Black Ass Slave? (3) ź "" <boobooililililil@roadrunner.com> wrote in message
news:480f2bc6$0$4087$4c368faf@roadrunner.com...
those at the fringes got varying voltage well below 100V depending on load.
"" <boobooililililil@roadrunner.com> wrote in message news:480f2bc6$0$4087$4c368faf@roadrunner.com...
Idiot. We had DC here 100 years ago. People near the hydro plant got 130V,
those at the fringes got varying voltage well below 100V depending on load.
P
Puppet_Sock
Guest
On Apr 22, 3:13 pm, Bret Cahill <BretCah...@aol.com> wrote:
in efficiency isn't very meaningful. The efficiency of a transmission
line depends on many things. And efficiency is received energy
divided by transmitted energy.
The situation where DC transmission is better is where the
transmission line is long compared to a 1/4 wavelength of
the AC transmission frequency. The typical transmission is
60 cps. So 3E8 m/s divided by 60/s, then divided by 4, is
1,250 km. So when you get transmission distances in
that range, radiative loss starts to be significant, and it
gets tough to match the impedance of the line to the load.
Basically what you get is a very large dipole antenna.
DC will remove that effect.
It's not a free ride though. DC transmission lines
require that you have high voltage DC to transmit. And most
generating stations do not produce DC. So you need to
get from AC to high voltage DC, and back to AC at the
receiving end. This is doable, but it
does have losses. It has only been relatively recently that
this process has been improved to the point of being useful,
say the last 20 years or so. This is because large scale
grids have been finding it useful to transmit power over
distances of that scale. So people found it worthwhile
to start doing the engineering to make the improvements.
Heh heh. A few years ago I was working at the head office
of Ontario Power Generation, writing software for their
power trading guys. The grid in Ontario is operated by
an agency called the IMO. They had a rule that if you
offered to sell power, but the grid was congested so that
you couldn't get it to the buyer, you got paid compensation.
A utility in Wisconsin noticed they could bid to sell power
in New York state, transmitting it through Ontario. And
they noticed that the connections were not large enough
to carry the amount of power they were offering, if there
was even a very small amount of power already on them.
Now the compesation was based on the difference between
what they offered to sell it for and what the buyer offered to
buy it for. So the guys in Wisconsin were essentially offering
it for free to assure they'd win the bid. But the buyers had
to pay for it at the market rate in NY. So basically, the guys
in Wisconsin were getting paid pretty much the full price.
They were getting paid *not* to sell electricity to NY
for many hours a day. And in amounts of 100's of MW.
The IMO very quickly had an emergency meeting and
changed the rules to disallow this.
Anyway, long distance transmission is sometimes done
on DC lines to reduce radiative loss.
Socks
Well, as others have ragged on about, the quoted change
in efficiency isn't very meaningful. The efficiency of a transmission
line depends on many things. And efficiency is received energy
divided by transmitted energy.
The situation where DC transmission is better is where the
transmission line is long compared to a 1/4 wavelength of
the AC transmission frequency. The typical transmission is
60 cps. So 3E8 m/s divided by 60/s, then divided by 4, is
1,250 km. So when you get transmission distances in
that range, radiative loss starts to be significant, and it
gets tough to match the impedance of the line to the load.
Basically what you get is a very large dipole antenna.
DC will remove that effect.
It's not a free ride though. DC transmission lines
require that you have high voltage DC to transmit. And most
generating stations do not produce DC. So you need to
get from AC to high voltage DC, and back to AC at the
receiving end. This is doable, but it
does have losses. It has only been relatively recently that
this process has been improved to the point of being useful,
say the last 20 years or so. This is because large scale
grids have been finding it useful to transmit power over
distances of that scale. So people found it worthwhile
to start doing the engineering to make the improvements.
Heh heh. A few years ago I was working at the head office
of Ontario Power Generation, writing software for their
power trading guys. The grid in Ontario is operated by
an agency called the IMO. They had a rule that if you
offered to sell power, but the grid was congested so that
you couldn't get it to the buyer, you got paid compensation.
A utility in Wisconsin noticed they could bid to sell power
in New York state, transmitting it through Ontario. And
they noticed that the connections were not large enough
to carry the amount of power they were offering, if there
was even a very small amount of power already on them.
Now the compesation was based on the difference between
what they offered to sell it for and what the buyer offered to
buy it for. So the guys in Wisconsin were essentially offering
it for free to assure they'd win the bid. But the buyers had
to pay for it at the market rate in NY. So basically, the guys
in Wisconsin were getting paid pretty much the full price.
They were getting paid *not* to sell electricity to NY
for many hours a day. And in amounts of 100's of MW.
The IMO very quickly had an emergency meeting and
changed the rules to disallow this.
Anyway, long distance transmission is sometimes done
on DC lines to reduce radiative loss.
Socks
B
Bret Cahill
Guest
If we can't get sustainable maybe we can signal ETs for help.
Bret Cahill
B
Benj
Guest
On Apr 22, 8:11 pm, tadchem <tadc...@comcast.net> wrote:
mathematical equations as if they were making sense and pretend to win
arguments by doing so? [I know it's common practice now] That is
"complete bollocks" to use Phil's colorful scientific argument! So
just what is 920% "efficiency"? I guess it's a transmission line where
nine times as much power comes out as you put in! That would be a
WONDERFUL way for Europeans to transmit power from the Sahara to
Europe! When mathematics doesn't agree with reality it is MATHEMATICS
that is thrown out!
You know, I need to introduce both you and Phil to another troll who
speaks latin and loves to correct people who speak "muttish".
Her Name is Autyme! [apparently nurse Ratched isn't letting her on
the ward computer these days]
Yes, AND 92% efficiency at the same time! Duh!
AND also twice as efficient! eg. 96% efficient. Moron.
Isn't it great when a so-called "scientist" can simply quote
mathematical equations as if they were making sense and pretend to win
arguments by doing so? [I know it's common practice now] That is
"complete bollocks" to use Phil's colorful scientific argument! So
just what is 920% "efficiency"? I guess it's a transmission line where
nine times as much power comes out as you put in! That would be a
WONDERFUL way for Europeans to transmit power from the Sahara to
Europe! When mathematics doesn't agree with reality it is MATHEMATICS
that is thrown out!
You know, I need to introduce both you and Phil to another troll who
speaks latin and loves to correct people who speak "muttish".
Her Name is Autyme! [apparently nurse Ratched isn't letting her on
the ward computer these days]
Sorry Tom, D+ on this one!
B
Bret Cahill
Guest
Never end sentences with prepositions.
Bret Cahill
B
Bret Cahill
Guest
Then rewrite the entire sentence:
"Bret doesn't know jack about how to express transmission line
efficiency."
Bret Cahill
T
tadchem
Guest
On Apr 23, 12:20 pm, Benj <bjac...@iwaynet.net> wrote:
<snip>
'efficiency.' It is *precisely* defined as a ratio - a mathematical
'equation' (whether you approve or not):
Note the various definitions here, used for specific cases.
http://en.wikipedia.org/wiki/Thermodynamic_efficiency
In all cases, the efficiency is the *ratio* of usable energy output to
total energy input. Since energy output cannot exceed input,
efficiency can never be greater than 1.
To multiplying the efficiency by 2x, you need to do something such as
double the output while maintaining a constant input. 96% efficiency
is therefore twice as efficient as 48% efficiency.
More apropos to the OP is the following article.
http://en.wikipedia.org/wiki/Electric_power_transmission#Bulk_power_transmission
"Transmission efficiency is improved by increasing the voltage using a
step-up transformer, which reduces the current in the conductors,
while keeping the power transmitted nearly equal to the power input.
The reduced current flowing through the conductor reduces the losses
in the conductor and since, according to Joule's Law, the losses are
proportional to the square of the current, halving the current makes
the transmission loss one quarter the original value."
While AC has slight radiative losses, DC has strong resistive losses.
In both, higher voltage means lower current is necessary to transmit a
given amount of power. AC can be easily (and efficiently) increased
in voltages through step-up transformers. High voltage DC is harder
and less efficient to produce and to use.
equations are definitions and not open to debate.
argument violates simple arithmetic?
2 x 92% is 184%, and 184% efficiency is impossible as efficiency is
defined.
Can you show me *HOW* 2 x 92% = 96%? I don't think so.
By my math, 96% = 1.04347826 * 92%, roughly.
Tom Davidson
Richmond, VA
No argument there.
<snip>
You obviously have a flawed understanding of the concept of
'efficiency.' It is *precisely* defined as a ratio - a mathematical
'equation' (whether you approve or not):
Note the various definitions here, used for specific cases.
http://en.wikipedia.org/wiki/Thermodynamic_efficiency
In all cases, the efficiency is the *ratio* of usable energy output to
total energy input. Since energy output cannot exceed input,
efficiency can never be greater than 1.
To multiplying the efficiency by 2x, you need to do something such as
double the output while maintaining a constant input. 96% efficiency
is therefore twice as efficient as 48% efficiency.
More apropos to the OP is the following article.
http://en.wikipedia.org/wiki/Electric_power_transmission#Bulk_power_transmission
"Transmission efficiency is improved by increasing the voltage using a
step-up transformer, which reduces the current in the conductors,
while keeping the power transmitted nearly equal to the power input.
The reduced current flowing through the conductor reduces the losses
in the conductor and since, according to Joule's Law, the losses are
proportional to the square of the current, halving the current makes
the transmission loss one quarter the original value."
While AC has slight radiative losses, DC has strong resistive losses.
In both, higher voltage means lower current is necessary to transmit a
given amount of power. AC can be easily (and efficiently) increased
in voltages through step-up transformers. High voltage DC is harder
and less efficient to produce and to use.
....and they do make sense, especially when you consider that these
equations are definitions and not open to debate.
I pretend nothing. Why do you pretend to understand when your
argument violates simple arithmetic?
2 x 92% is 184%, and 184% efficiency is impossible as efficiency is
defined.
Can you show me *HOW* 2 x 92% = 96%? I don't think so.
By my math, 96% = 1.04347826 * 92%, roughly.
An egregious error, just as wrong as claiming that 2 x 92% = 96%
Tom Davidson
Richmond, VA
T
tadchem
Guest
On Apr 23, 4:06 pm, Bret Cahill <BretCah...@aol.com> wrote:
Astor.
On one occasion she accused the PM of ending a sentence with a
preposition.
Churchill replied, IIRC, "Madam, that is an accusation up with which I
shall not put."
Tom Davidson
Richmond, VA
An infamous feud was carried on between Winston Churchill and Lady
Astor.
On one occasion she accused the PM of ending a sentence with a
preposition.
Churchill replied, IIRC, "Madam, that is an accusation up with which I
shall not put."
Tom Davidson
Richmond, VA