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Science Forum Index » Physics Forum » Why Is DC Power Transmission 10X More Efficient Than AC?
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| Phil Allison |
 Posted: Tue Apr 22, 2008 6:55 pm |
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"Bret Cahill = TROLL "
Quote:
** What is 10 times more efficient than 92 % ??
Going 10X further with the same 8% loss?
One tenth as lossy for the same distance?
** No way either of those things is expressed the fuckwit way you came up
with.
......... Phil |
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| Phil Allison |
| Posted: Tue Apr 22, 2008 7:11 pm |
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"Paul E. Schoen"
Quote: The losses in electrical transmission have increased from about 5% to 9.5%
in recent years, so efficiency is 90.5% to 95%.
** Transmission * loss percentage * increases with the amount of load -
plus the overall energy lost depends on load levels and time.
The operating efficiency percentage of a transmission link cannot be known
stated unless the load is too.
** Total BOLLOCKS !
Quote: I would assume that a tenfold increase in efficiency would be a tenfold
reduction in losses,
** Why ?????
It makes nonsense of the English language.
One can increase the efficiency percentage OR reduce the loss percentage
by a number.
When the efficiency percentage is low, you use the former and when it is
high, the latter.
...... Phil |
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| Paul E. Schoen |
| Posted: Wed Apr 23, 2008 1:03 am |
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"Phil Allison" <philallison@tpg.com.au> wrote in message
news:677d5oF2nj34rU1@mid.individual.net...
Quote:
"Paul E. Schoen"
The losses in electrical transmission have increased from about 5% to
9.5% in recent years, so efficiency is 90.5% to 95%.
** Transmission * loss percentage * increases with the amount of
oad - plus the overall energy lost depends on load levels and time.
The operating efficiency percentage of a transmission link cannot be
known stated unless the load is too.
Of course. There has been an increase in demand without a corresponding
increase in the infrastructure, so the power grid is more heavily loaded.
Being largely dependent on I^2R losses, a 50% increase in demand (current)
results in a doubling of losses.
Quote:
According to http://en.wikipedia.org/wiki/Electric_power_transmission,
power losses were about 7.2% in 1995. And according to
http://en.wikipedia.org/wiki/High-voltage_direct_current, HVDC
transmission losses are about 3%. So a tenfold increase in efficiency
seems unreasonable.
** Total BOLLOCKS !
I would assume that a tenfold increase in efficiency would be a tenfold
reduction in losses,
** Why ?????
It makes nonsense of the English language.
One can increase the efficiency percentage OR reduce the loss
percentage by a number.
When the efficiency percentage is low, you use the former and when it is
high, the latter.
A tenfold increase means ten times better. 99% is twice as good as 98%,
because it costs me half as much in losses. So it is a 100% increase in
efficiency, or a 50% reduction of losses.
A similar situation exists with accuracy, but it is reversed in meaning. A
1% instrument is really 99% accurate, so an instrument that is twice as
good is 0.5%. A 100% increase in accuracy, but the accuracy figure is
really a statement of inaccuracy.
So, when one tries to develop a more accurate instrument, the goal would
more reasonably be to make it like 10% more accurate or 50% more accurate,
which are easy to comprehend. To say one wanted to increase the accuracy of
an instrument by 1% would be reasonable if one knew it to be 2%, but would
be impossible if it were already 1% or better.
The same with efficiency, but it is better understood in terms of reducing
losses.
But you are right that it does put strains on English language usage.
Paul |
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| Phil Allison |
| Posted: Wed Apr 23, 2008 1:31 am |
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"Paul E. Schoen"
Quote: "Phil Allison"
The losses in electrical transmission have increased from about 5% to
9.5% in recent years, so efficiency is 90.5% to 95%.
** Transmission * loss percentage * increases with the amount of
oad - plus the overall energy lost depends on load levels and time.
The operating efficiency percentage of a transmission link cannot be
known or stated unless the load is too.
Of course. There has been an increase in demand without a corresponding
increase in the infrastructure, so the power grid is more heavily loaded.
Being largely dependent on I^2R losses, a 50% increase in demand (current)
results in a doubling of losses.
** Try learning to bloody READ - you imbecile !!!!
The PERCENTAGE loss of the transmission line is a *varying quantity* with
load.
The numbers you quoted are NOT measures of the energy efficiency of the
transmission lines.
Quote: I would assume that a tenfold increase in efficiency would be a tenfold
reduction in losses,
** Why ?????
It makes nonsense of the English language.
One can increase the efficiency percentage OR reduce the loss
percentage by a number.
When the efficiency percentage is low, you use the former and when it is
high, the latter.
A tenfold increase means ten times better.
** Asinine, idiotic shite.
A " tenfold increase " can only mean a 10 times increase in a quantity.
LEARN to READ !!
Quote: 99% is twice as good as 98%, because it costs me half as much in losses.
** So must be stated as 50% reduction in losses.
( snip more reams of mind numbing, fuckwit drivel )
Quote: But you are right that it does put strains on English language usage.
** It is purest fuckwittery and a misuse of meaning.
....... Phil |
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| Michael Moroney |
| Posted: Wed Apr 23, 2008 4:26 am |
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Bret Cahill <BretCahill@aol.com> writes:
Quote: Is there some low frequency radiation or hysterisis loss or what?
I won't argue the "10 times" part, but DC power transmission is more
efficient because:
Line inductance and capacitance are unimportant with DC. With AC they
contribute to "imaginary" power, where the system has to transmit power
(with losses) that does no work, because voltage and current are out of
phase.
Line radiation. I don't know how big an effect this is.
DC utilizes a line 100% of the time. An AC insulator has to withstand
the peak AC voltage (1.414 times the RMS value) but most of the time the
instantaneous voltage is lower and thus the instantaneous power is also
lower. It even goes to zero twice per cycle. A DC line will remain at the
peak voltage 100% of the time. Which will fill a kiddie pool faster, a
garden hose left on or a garden hose repeatedly turned off and on? |
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| Puppet_Sock |
| Posted: Wed Apr 23, 2008 4:53 am |
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On Apr 22, 3:13 pm, Bret Cahill <BretCah...@aol.com> wrote:
Quote: Is there some low frequency radiation or hysterisis loss or what?
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 |
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| Bret Cahill |
| Posted: Wed Apr 23, 2008 6:04 am |
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Quote: 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.
If we can't get sustainable maybe we can signal ETs for help.
Bret Cahill |
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| Benj |
| Posted: Wed Apr 23, 2008 6:20 am |
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On Apr 22, 8:11 pm, tadchem <tadc...@comcast.net> wrote:
Quote: On Apr 22, 6:05 pm, Benj <bjac...@iwaynet.net> wrote:
The OP's question is an absurd troll.
Like you.
...... Phil
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.
That's 8% INefficiency
Yes, AND 92% efficiency at the same time! Duh!
Quote: TWICE as efficient would only have 4% of the
energy lost or would be 96%.
Your 4% would be HALF as INefficient; not at all the same thing.
AND also twice as efficient! eg. 96% efficient. Moron.
Quote: 10 x 92% is still 920%.
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]
Quote: The interested student can take it from
there...
Sorry Tom, D+ on this one!
Quote: Since 10X would be more than 99% efficient I am somewhat skeptical
that even modern converters can produce so little loss.
Tom Davidson
Richmond, VA |
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| Eric Gisin |
| Posted: Wed Apr 23, 2008 8:41 am |
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""Black Ass Slave? (3) ¼  "" <boobooililililil@roadrunner.com> wrote in message
news:480f2bc6$0$4087$4c368faf@roadrunner.com...
Quote: Bret Cahill wrote:
Is there some low frequency radiation or hysterisis loss or what?
It's not more efficient. That's why Edison's DC power idea failed and Westinghouse's AC
prevailed.
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. |
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| Bret Cahill |
| Posted: Wed Apr 23, 2008 10:06 am |
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Never end sentences with prepositions.
Bret Cahill |
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| Guest |
| Posted: Wed Apr 23, 2008 10:45 am |
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In sci.physics "Blattus Slafaly ? (3) ? " <boobooililililil@roadrunner.com> wrote:
Quote: Bret Cahill wrote:
Is there some low frequency radiation or hysterisis loss or what?
Bret Cahill
It's not more efficient. That's why Edison's DC power idea failed and
Westinghouse's AC prevailed.
Apples and oranges.
Power companies are out to make money.
The economic cost of losses for a DC system can be significantly less
than that of an AC system over long distances.
For short distances, the cost of the losses are generally less than
the cost of the conversion equipment, so AC is usually used.
There are many reasons why a DC system would be prefered depending
on the situation.
Start here:
http://en.wikipedia.org/wiki/Hvdc
--
Jim Pennino
Remove .spam.sux to reply. |
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| Richard Tobin |
| Posted: Wed Apr 23, 2008 11:33 am |
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In article <068b228f-f5c8-44af-8fb2-a633bd413666@24g2000hsh.googlegroups.com>,
Benj <bjacoby@iwaynet.net> wrote:
Quote: 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%.
Your terminology seems pointlessly confusing. Presumably you think
a 100% efficient system is 20 times as efficient as another 100%
system.
The simple answer is that if something is 92% efficient, you can't
make it 10 times more efficient.
-- Richard
--
:wq |
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| Bret Cahill |
| Posted: Wed Apr 23, 2008 12:02 pm |
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Quote: you came up
with.
Never end sentences with prepositions.
But it sounds funny to say, "up with which you came."
Then rewrite the entire sentence:
"Bret doesn't know jack about how to express transmission line
efficiency."
Bret Cahill |
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| tadchem |
| Posted: Wed Apr 23, 2008 2:02 pm |
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On Apr 23, 12:20 pm, Benj <bjac...@iwaynet.net> wrote:
Quote: On Apr 22, 8:11 pm, tadchem <tadc...@comcast.net> wrote:
snip
Quote:
That's 8% INefficiency
Yes, AND 92% efficiency at the same time! Duh!
No argument there.
<snip>
Quote:
Your 4% would be HALF as INefficient; not at all the same thing.
AND also twice as efficient! eg. 96% efficient. Moron.
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.
Quote: Isn't it great when a so-called "scientist" can simply quote
mathematical equations as if they were making sense
....and they do make sense, especially when you consider that these
equations are definitions and not open to debate.
Quote: and pretend to win
arguments by doing so?
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.
Quote: [I know it's common practice now] That is
"complete bollocks" to use Phil's colorful scientific argument! So
just what is 920% "efficiency"?
An egregious error, just as wrong as claiming that 2 x 92% = 96%
Tom Davidson
Richmond, VA |
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| tadchem |
| Posted: Wed Apr 23, 2008 2:09 pm |
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On Apr 23, 4:06 pm, Bret Cahill <BretCah...@aol.com> wrote:
Quote: you came up
with.
Never end sentences with prepositions.
Bret Cahill
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 |
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