Comment Preferences

• Pretty awesome(50+ / 0-)

How much would it cost to replace these I wonder.  Also, can the cables handle the extra current without burning?  Still, neat idea

Hay hombres que luchan un dia, y son buenos Hay otros que luchan un año, y son mejores Hay quienes luchan muchos años, y son muy buenos. Pero hay los que luchan toda la vida. Esos son los imprescendibles.

• oh boy. Ohm's law?(25+ / 0-)

This is dusting off some very cobwebby memories, but if V = IR, given a constant resistance, doesn't the current increase linearly with voltage?

(ouch.  I think I may have strained something in my brain)

Hay hombres que luchan un dia, y son buenos Hay otros que luchan un año, y son mejores Hay quienes luchan muchos años, y son muy buenos. Pero hay los que luchan toda la vida. Esos son los imprescendibles.

[ Parent ]

• only if total power consumption goes up...(47+ / 0-)

In your equation, if voltage went up, current would actually go down to make the equation stay in balance.

The equation you need to consult is P=I*V

So, if the total power requirement goes up, the current will go up (regardless of the voltage). This is why power lines can sag on hot days when there is a lot of power being consumed.. a lot of current running through the lines, and heating up the lines...

Freedom isn't free. So quit whining and pay your taxes.

[ Parent ]

• And more directly(14+ / 0-)

P = R* I^2

or

P = R / V ^2

which is what gives you the 6x decrease in power loss for a 2.5x increase in voltage (resistance of the cable is the same).

[ Parent ]

• Actually, the second equation is:(6+ / 0-)

P = V^2 / R

and I'm not sure how you draw the conclusion you do.

The man who moves a mountain begins by moving away small stones. -Confucius

[ Parent ]

• You're right(5+ / 0-)

I screwed up the 2nd equation, but it's important to realize which V you're talking about. When it comes to losses in the transmission line, the V is the voltage drop across the line (which will be lower at lower I), not the input voltage.

So, at higher voltage at constant delivered power, the current will be lower and the reduced power loss will go like the square of the decreased current.

[ Parent ]

• Here's a link to a handy ohms law calculator(1+ / 0-)
Recommended by:
kyril

usually the square chart is shown as a circle, but all the formulas are correct.  There are also some 3 phase AC formulas that one might find useful.

http://www.angelfire.com/...

Google Ohm's Law Calculator to find more.

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• You also need to change the transformer at each(2+ / 0-)
Recommended by:
goodpractice, kyril

end of the powerline to both boost the voltage on the line, and to step it down to distribution useful voltages, like 13,800 line to line, 7200 line to neutral distribution lines and such.

The transformers in the switchyard also have to have sufficient distances between phases to handle the magnetic forces that are generated, so it isn't as easy as it may seem, just to boost voltage.  Before it can be done, there is also an arduous and fairly long term process to modify standards for cross country powerlines and towers before this kind of change can be implemented.  So the regulatory environment must also change as well as the crossbars.  Much study for wind and ice loading, capacitance, effects on power factor correction and a lot more needs to be done before changes can be made.

But I like the idea, and agree with the higher efficiency of high voltage long distance power transmission.

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• In general(2+ / 0-)
Recommended by:
kyril, Ohiodem1

our national grid is long overdue for an upgrade, and boosting long-haul interconnections is going to be a major part of any strategy that relies on localized renewable sources.

Seems like a good time to revist the 'standards' for high voltage transmission and make the needed changes to reduce transmission losses, especially if it can be done relatively cheaply.

[ Parent ]

• This is not true!!! And I think a bit confusing...(18+ / 0-)
In your equation, if voltage went up, current would actually go down to make the equation stay in balance.
Actually, current would increase to meet Ohm's Law.

What Mindful Nature is confusing is the placement of the voltage and load (resistance) when applying ohm's law. Each household represents a load. The voltage at the house is still going to be the same! That's the key! People are most familiar with 120V lines in their house. Their house is still going to draw the same average current at the same 120V voltage. So even their power consumed will also be the same. And that makes sense! So what are we changing?

We are changing (boosting) the transmission voltage going to the house and inserting new transformers to step that larger transmission voltage back down to 120V at the load (home). So it's a more complex circuit than a single voltage, current and resistance. You can't apply V=I*R to anything more than a single, lumped-parameter resistance.

The transmission line itself can be modeled as a very, very small resistance. That's why it is used as a conductor! And any current flowing through the line will generate a very small voltage across that line segment. That is where V=I*R does apply directly to the transmission line. But the voltage across the transmission line that we are talking about is very small relative to the voltage being carried by the line in relation to overall circuit ground.

What is saved/reduced here is the amount of current required at the load end of distribution, specifically at the transformer. A higher voltage on the primary/transmission-line side of the transformer means less current is needed on that same side of the transformer for a fixed power load. The power load is determined by the secondary/household side. This is where P=V*I applies. So if P is fixed for the house (which it is), a larger voltage allows a proportionally smaller current.

So if the voltage on the transmission lines can be higher, the current needed in those same transmission lines to deliver the original amount of power to the homes is smaller. And with less current in the transmission lines, there is less loss. And with less loss, there is more overall efficiency.

I think. ;)

The man who moves a mountain begins by moving away small stones. -Confucius

[ Parent ]

• Yeesh, I'll just come right out and say,(21+ / 0-)

I don't understand a lot of what you guys are talking about, but man do I love running across conversations like this on dkos. Cheers!

And my baby's my common sense, so don't feed me planned obsolescence.

[ Parent ]

• Simple(9+ / 0-)

Power transmitted = Current * Voltage.

To transmit a given amount of power (what your wind farm produces), the higher the voltage you can transmit at, the lower the current.  Since the transmission wires have a resistance that depends on the size (cross section) and length of the cable, and is thus fixed, unless we rebuild the whole thing, the power lost in transmission because of the resistance of the transmission wires is:

Power lost = current * current * resistance.

Thus, doubling the voltage at which the power is transmitted, for a given power to be transmitted, that  reduces the current by a factor of 2, and the power lost is reduced by a factor of 4.

• A lot of people don't understand (7+ / 0-)

these basic concepts & relationship between Power, Voltage and Current. These all refer to very different things, but in common speech, people often interchange them. I'm sure you can imagine that to an EE it's like fingernails on a chalkboard.

Sometimes it helps to use an analogy:
Here's one...

Freedom isn't free. So quit whining and pay your taxes.

[ Parent ]

• Yup, DKos is awesome that way. Gawd, I love smart(3+ / 0-)
Recommended by:
side pocket, deha, kyril

people. :-)

Information is abundant, wisdom is scarce. The Druid

[ Parent ]

• I think the source of the confusion is (5+ / 0-)

that "voltage" in the familiar V=IR is a different quantity than "voltage" in "high voltage power lines."  V=IR would apply to the voltage lost over the length of the cable, with appropriate caveats as the equation really applies to direct current.  "High voltage" would be the amplitude of the alternating voltage in the transmission line, akin to the "120 V" of household supply.

Sorry, just had to chip in to work some of the cobwebs out of that section of my brain.  Your post was informative and, as far as I can tell, correct.

that art thou

[ Parent ]

• Huh?(2+ / 0-)
Recommended by:
KenBee, Ohiodem1

You said what I wrote was "not true", then came to the same conclusion:

if the voltage on the transmission lines can be higher, the current needed in those same transmission lines to deliver the original amount of power to the homes is smaller.
That's exactly what I was saying... just using a simple equation. Actually all these equations are very powerful, and mostly universal.

Freedom isn't free. So quit whining and pay your taxes.

[ Parent ]

• The portion...(1+ / 0-)
Recommended by:
kyril

I highlighted and immediately corrected is at the top of my comment. About ohm's law. It has nothing immediately to do to with your conclusion. Here it is again:

In your equation, if voltage went up, current would actually go down to make the equation stay in balance.
This is not true.

The man who moves a mountain begins by moving away small stones. -Confucius

[ Parent ]

• sure it is...(1+ / 0-)
Recommended by:
Ohiodem1

example:

P=I*V

P=200
I=10
V=20
200 = 10 * 20

Now, increase the voltage, but keep power the same:

P=200
I=x
V=40

solve for I...

I=5

voltage went up... current went down.

Freedom isn't free. So quit whining and pay your taxes.

[ Parent ]

• First, let me apologize. I have a relative in the (1+ / 0-)
Recommended by:
kyril

hospital. It's a bit stressful here. So my tone is quick, short, poor and not like me normally. Really. I am sorry. Normally I would elaborate at length and be very subtle about my feelings.

Second, your comment seems very strongly to be responding to Mindful Nature's comment. I mean it is a reply to that comment after all. So the expression 'your equation' seems to refer to the equation he cites, namely ohm's law. You even go on then to say that the equation he needs is a different equation, namely the power equation.

Do you see the confusion there? Again, sorry that I am a bit short and thus less subtle/polite (ergo, dickish) tonight. Things are nasty here and I am using dKos as an escape. I felt like more perspective and clarity would reduce confusion.

The man who moves a mountain begins by moving away small stones. -Confucius

[ Parent ]

• Oh, I see..(0+ / 0-)

no problem... happens all the time, these threads are hard to keep straight. I hope your relative gets well soon. There are certainly  more important things in life than discussing power equations on the internet.

Freedom isn't free. So quit whining and pay your taxes.

[ Parent ]

• I agree with this. nt(1+ / 0-)
Recommended by:
kyril

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• Limited by the transformer's impedance(2+ / 0-)
Recommended by:
flitedocnm, kyril

What comes out of the high-voltage transformer is high voltage and (relatively) low current. You can increase the voltage in an AC system without increasing the current.

• Ohm's Law in this case(6+ / 0-)

applies to the voltage drop along the wire.  The wire is of fixed resistance (resistivity, technically, but the particular wire is of fixed cross section, material, and length, so the resistance is fixed).  By V=IR, with R fixed, V is proportional to I.

(Just a word of warning here.  I'm a VI-3 -- computer science -- guy, and this is VI-1 -- electrical engineering.  Back at that little trade school on the north bank of the Charles, they combine electrical engineering and computer science into one department, which they, and we, fondly or otherwise refer to as Course VI.  We VI-3's had to get our hands dirty with actual circuits, though; they wouldn't let us become full Ancient and Honorable Nerds of the Infinite Corridor without it.  So that's where my knowledge, such as it is, comes from.  You can imagine the various puns on "Course Six".  And you can Google 'em.  But I won't go there, beyond noting that there's now a VI-2, which is a middle ground between VI-3 and VI-1.  Think of VI-2 as the Very Serious People inside the Beltway who are constantly advocating compromise.  The "VI" in this paragraph has nothing to do with V and I elsewhere in this screed, although I'm sure there are VI-1's who would beg to differ.)

Again, V in this case refers to the voltage drop along the length of the wire.  It's independent of the voltage difference between the two wires in the circuit, but it's why the efficiency of transmission improves so dramatically with higher voltage.

The other thing to remember is that P=IV (power is the product of current and voltage).  If we step up the voltage, we require proportionately less current for the same amount of power.  But remember in this case the voltage is the generated voltage. not the voltage drop along the wire.

So let's try an example.  Suppose we have a power line that we want to carry 1 gigawatt of power (I don't know what the actual numbers are; they're probably much lower for any given wire, but whatever).  If we transmit that power at 400 kilovolts (KV), it will require 2500 amperes.  Now let's suppose the total resistance of the power line is 40 ohms (again, I don't know what the resistance of real world power lines is).  To sustain a current of 2500 amperes through 40 ohms requires 100 KV (at the other end, you'll see only 300 KV).  100 KV * 2500 ohms is 250 megawatts.  So fully 1/4 of the power is wasted.

Now, let's transmit that power at 1 megavolt (MV).  This requires only 1000 amperes.  With a 40 ohm resistance, that will be 40 KV voltage drop along the power line; the far end will see 960 KV.  So instead of 25% loss, there's 4% loss.  25 divided by 4 is...let's see...6.25.  The factor of 6.

There are other problems with the higher voltage.  Air has finite resistance, so there will be some losses by conduction through the air.  But the efficiency should still increase by a lot.

[ Parent ]

• Ah, but what about power factor?(6+ / 0-)

Dusting off my old EE degree, and remembering all those months in power class... (some of the lab sessions could get kind of exciting), when AC is involved you can never neglect the power factor.  This is a bad thing in electrical distribution systems, and it happens when the sine waves of the current flow are out of phase with the sine waves of the voltage.

Numerous parts of the generation and distribution network become less efficient when the power factor is large.  Utilities go to great expense to counteract the effects of power-factor-boosting things.   Impedance of power lines, transformers, and the loads those annoying customers insist on connecting, all contribute to an increase in the out-of-phaseness.   The motor in your refrigerator, for instance.

If I remember correctly (it has been some decades) power factor arises from the current phase being retarded behind the voltage phase, and the retardation effect goes up with the amount of current in the lines.  So increasing the transmission voltage and thus decreasing the current, could have the additional benefit of decreasing the power factor effect of the lines.

I can't remember how much this amounts to in the total schema of things - my summer jobs in the electrical industry were limited to the Distribution Department (from the sub-station to your house), not the long distance Transmission Department, where all these high voltage thingies happen.   We are talking upwards of a million volts, here.   Quite spectacular when one of those insulators fails.   We had a lab where such things were made to happen on purpose.  Like a scene out of Frankenstein.

A really interesting case is Japan, where half of the country runs on 50 Hz power and the other half on 60 Hz.  You can't easily convert one to the other at these power levels, and if you change the frequency, you also change our old friend the power factor.  So to enable power sharing around the country, Japan has had to build some really big motor-inverter sets, and also really big vacuum tubes to do this.

It works out that actually using DC for long distance transmission has some benefits.  No power factor losses at all.  But again, big converters at both ends.

Though ones hates to think that Edison might have been right about something.

• Poor power factory simply means(5+ / 0-)

that you need to increase the current to deliver the same amount of usable power to the load(s), because the voltage and current are out of phase. The usable (real) power delivered is P = IR cos p where p is the phase angle (how many degrees out of phase the voltage and current are), and cos p X 100%  is the power factor - bigger is better, perfect is p = 0, cos p = 1, PF = 100%.

So if you need 120 watts at 120v, in phase you need 1 Amp. With a phase angle of 30 degrees, PF = 87% and you now need 1.15 amps (15% more current) to service the same 120 watt load. If the wire's resistance in 1 ohm, you'd lose 1 watt in transmission with 100% PF, but 1.3 watts (30% worse) with 87% PF. (There are also 18 watts of "imaginary power", or the nameplate rating on a single device with 87% PF would 138 VA instead of 120 watts - VA is Volt-Amps).

In places that use a lot induction motors (like factories), they install large banks of capacitors to bring the voltage and current closer to in phase. They do this not because they want to save energy, but because the electric utility charges them for three things: the power they actually use, the power factor they use it at, and demand (sort of the peak power they draw).

Computer power supplies also have terrible power factor, but residential and commercial users usually don't pay for it, directly anyway. You can buy power factor corrected computer power supplies to replace the original equipment. If decent power factor were mandated, given the huge number of computers and other electronic equipment, there would be a large energy savings.

Frequency affects power factor only because it affects impedance - the imaginary or reactive part of impedance varies with frequency, so that affects the phase angle between V and I.

Edison was still wrong, because the technology to step up or step down DC efficiently has only existed in the last 30-40 years or so. But DC transmission lines don't suffer from reactive losses like AC lines do. They still have to deal with ohmic losses.

Modern revolutions have succeeded because of solidarity, not force.

[ Parent ]

• I agree with this discussion. Power factor(0+ / 0-)

can be corrected at the user, and also at the electric switchyard.

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• I'm not even a VI-1(0+ / 0-)

But I do remember cramming all those equations into my head many years ago, the night before a physics 1 exam. But how can the equation V = IR suggest anything other that at a given resistance, if you increase V then you increase I?

• If you have a perfect voltage source(0+ / 0-)

then increasing the voltage across a particular resistance will increase the current proportionately.  But in practice, any voltage source (like a battery) has an internal resistance, which sums with the load (and transmission) resistance.

But what's actually going on is that we have a power source -- something that generates a constant (at least at a given point in time) IV.  If we increase the voltage of the power source, we correspondingly decrease the current.

[ Parent ]

• It's not Resistance that costs you(2+ / 0-)
Recommended by:

It's hysteresis, the alternating current.  Current flow lags voltage and that creates big losses in long transmission lines.  The best solution is high voltage direct current.  Upwards of 500,000 volts DC.  Current is relatively low, which limit losses due to resistance.  You convert 3-phase alternating current to direct current, transport it as DC, then convert ot back to AC at the receiving end.

• Bravo(0+ / 0-)

Nicely done.

-5.38, -2.97
The NRA doesn't represent the interests of gun owners. So why are you still a member?

[ Parent ]

• double the power for given cable budget?(1+ / 0-)
Recommended by:
PrahaPartizan

Three-phase ac power is a thing of beauty, perhaps it made Tesla go crazy.

Three wires carrying ac voltage, spaced 1/3 apart in the cycle.  If each carries the same magnitude (yet sinusoidal) current, the total power delivered to the load is dead flat. No variation in power at all, no more sinusoid, unlike a household outlet which delivers fluctuating sinusoidal power. (you have Excel? good, do the math ;)

That's why old school machine tools use three-phase motors, removing 60 Hz variations in torque causing distortions in the cutting.  The only thing cleaner (because three phase currents maybe not perfectly equal) is to use DC power.  The old WWII and later Monarch lathes had massive vacuum tube rectifiers/amplifiers to run the motors on DC, which is completely flat, not to mention a joy to speed-control.

Back to the point, DC uses two wires.  For power line transport it has no continuing losses from those energy-eating reactive things like capacitance and inductance, which only dine when voltages are changing.

That is one advantage.  The other is the possibility of using Mother Earth herself as the return line (sometimes called earth or ground), so only one "hot" wire is deployed, so for the same money it can be thicker than two smaller ones. That was talked about years ago, not sure where it stands now.

• Thomas A. Edison lost this battle to George(1+ / 0-)
Recommended by:
eyesoars

Westinghouse.  Line losses make long distance transmission of DC current far less efficient than AC.

From Smithsonian, an article of their rivalry:

http://blogs.smithsonianmag.com/...

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• DC is not less efficient.(3+ / 0-)
Recommended by:
jam, Ohiodem1, justajoe

At a given voltage, DC has lower losses than AC.  Also takes fewer wires.  The problem is that it's harder to make DC at very high voltages than AC.  It used to be a lot harder.  The problem is, to switch AC, you just need a transformer; the voltage conversion is the ratio of the number of turns between the two coils.  But that doesn't work with DC because transformers work by induction (changing magnetic fields inducing a current in a different conductor), and since DC is constant, its magnetic field is constant, and thus, no induction.  So they used to have to make motor-generators where a DC motor spins a DC generator.  A super-high-voltage, high power DC generator.  Not a cheap or easy task, inefficient, high maintenance, etc.

Nowadays though modern switching electronics makes high voltage DC power transmission realistic and a better than AC in certain circumstances.  That is, instead of a motor generator, power is stored (capacitors, magnetic fields, whatnot), raising the potential of a discharge.  The problem is that due to the fact that power is voltage times current, and you're discharging at a higher voltage, the discharge inherently can only run for a fraction as long as you're charging it.  So you must charge and discharge multiple banks together, in succession, with something carefully keeping them in phase.  And to do this well and affordably takes super-high-power (both voltage and current) electronics like FETs which didn't become widely available and affordable until relatively recently.

Basically, HVDC requires relatively expensive switching stations instead of simple transformers but saves on wire cost for a given amount of current transfer - thus it excels at long run transmission but is not economically viable for short runs - on land at least (in saltwater it's pretty much a "must", as AC induction losses in saltwater are huge (remember, changing magnetic field + conductor (aka seawater) = inductive currents).  HVDC is also nice in that it lets you easily exchange power with out-of-phase grids and even grids operating at different frequencies.

Anyway, the diarist and many of the commenters have got a lot of this backwards.

1) The innovation is not the concept of having the arms be nonconductive.  This is patently obvious to anyone designing a tower that the distance between a wire and the first thing its capable of discharging to is going to limit your voltage, and so your design has to balance tradeoffs of cost, strength, and discharge voltage.  The innovation here is a ready system to uprate existing lines by effectively insulating their existing arms.

2) The problem being addressed concerning wind is not "power line losses".  There's actually rather little power lost in the grid - the US average is nearly 93% efficiency, power plant to point of consumption.  The issue at hand is maximum power transmitted.  You can only pump so much current through a line before the wires start to overheat and sag too much.  But since power is current times voltage, if you increase the voltage you increase the power even if the current remains fixed.  That is, you can transmit more power without building whole new lines if you do this relatively minor retrofit to existing lines.  These lines are not "poorly designed" in that they couldn't handle the higher voltages; the issue is when they were built, there was no need for higher voltages, for more power to be transmitted.  But when you suddenly put all of this new generation capacity in the middle of nowhere, suddenly there is a need that these existing lines can't meet on their own.

Which makes me think of something.  One would expect that the windier (and especially, the rainier) the day, the faster heat would be lost from the conductors, and thus the more current they should technically be able to handle.  Yet the lines are designed for a specific max current given the rate of cooling in calm air on a hot day.  Windy days are also when the most wind power generation occurs.  I wonder if they could actually simply uprate many lines by... doing nothing.  Simply measure or estimate line temperature under the current conditions and change how much current you limit yourself to based on it.  Or is that being done already somewhere?

Another thing the conversation makes me think of: I wonder if eventually, now that DC switching is much more easily accomplished, if  people will move over to DC power for home distribution (DC sockets instead of AC).  Takes 5 times as much DC current to feel a spark as AC and is far less likely to kill you for a given current (despite the lack of skin effect) and less wiring is needed.

[ Parent ]

• I've thought of it(0+ / 0-)

I call this an "IBM problem". There's an old saying about new technology - "nobody ever got fired for buying IBM." In other words, go with what works.

I tried to convince a team of engineers that we could go with a smaller, cheaper transformer at a low/medium wind site because of
1) line losses
2) efficiency losses
3) wind conditions - i.e. the wind farm would only be producing full power something like 200 hours per year, or about 2.2% of the time.

Taking all of that into account, you can run a transformer hot (105-120% of rated capacity) - utilities do it all the time during peak loads.

I was completely ignored and belittled for the idea, so we spent an extra \$200K.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• Ah, the old oversimplistic view of safety factors.(2+ / 0-)
Recommended by:
Ohiodem1, jam

"The book / the official documentation / whatever says that this is the safe X for device Y, so we can always run at X, and we can never exceed X."

The real world is, of course, not that simple, and depends on the circumstances of how you're operating.  Sometimes your circumstances are such that your safety factor for device Y becomes compromised if some other system fails, and so it's not really a safety factor at all.  Sometimes you gain additional safety from a whole host of other factors related to other systems and so the safe X for device Y is actually way higher and you're wasting money pointlessly.  Systems must always be looked at as a whole, not as a sum of individual components.  Here's all of the possible use cases, here's all of the possible failures - what happens when we combine them and what are the odds of that situation?  Yes, that's a more challenging analysis, but that's the dang reason why engineers take home a salary, to do the analysis right.

I see this sort of attitude a lot in discussions about wiring.  For example, I've heard a lot of electrical engineers argue that fast charging of electric cars is impossible without dangerously high voltages.  Why?  Because "the book" shows you the maximum rated current for a cord of given thickness with various insulators, and oh look, the cord would have to be too thick to bend or lift!  Great... except "the book" is talking about constant current flow in simple, fixed applications.  That's not taking into account that it takes time for a cord to heat up enough to where you're burning the insulation or risking irreversible deformation, and even if you get to that point, all you have to do to counter it is cool the cord.

[ Parent ]

• And some transformer standards are built around(1+ / 0-)
Recommended by:
jam

a concept that if you use the transformer within its ratings, 100 per cent of the time, you can expect some figure, X hours, frequently I have seen the number 20,000 hours as the expected life.  So, if you run it above its ratings, then that number 20,000 hours may be expected to drop to maybe 19,000 hours if the temperature excursion is defined and predictable.

Design activity may be undertaken to account for temperature excursions as well.  If for instance the insulation system rating is 180 Deg C, and the excursions would dictate a rating of 220 Deg C, then the act of purchasing the 220 Deg C insulation system may be a low cost alternative to a bigger transformer.  You are sized for 95 per cent of usage, with capability to handle a larger load 5 per cent of the time, without degradation of the expected life of the transformer.

On the example of cool the cord, in my opinion, I believe a better, more reliable solution is to purchase a cord or cable with a higher temperature rating, for instance, replacing a 90 deg C wire with 105 or 130 Deg C wire which has higher ampacity in the first place and can take the higher operating temperature, which of course is a fire risk if the wire is used in excess of its capacity.  I have long experience in the electrical safety business, and if you submitted that kind of arrangement to a certification lab, it would be rejected out of hand.

Alternately, if short term current excursions were expected, you could put a duty cycle rating on it  to cover for the excursion, but duty cycles are cumbersome and some consumers would ignore them, leading to a fire or electrical shock risk.

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• that was the other thing(0+ / 0-)

temperature, I forgot. The highest winds (at this location) were only during the winter with ambient temps usually around 0-10 C. And the transformer we put in is ONAN. If temperature became a problem, they could always slap a couple of pumps on it to become OFAF, right?

Ultimately, I'm not a transformer guy, I'm a little wires guy.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• Had to look up ONAN and ONAF(0+ / 0-)

A succinct explanation is here:

http://www.pacificcresttrans.com/...

They agree that adding forced air cooling to make ONAN an OFAF is an acceptable procedure.

About 20 years ago, I was more knowledgable about transformers than I am now.

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• The cord cooling approach is actually being used..(0+ / 0-)

because realistically you need an order of magnitude or so better cooling than passive air cooling alone can provide, not something that a mere uprating of wire type or insulation can provide.  Rapid charging can be hundreds of amps for 5-15 minutes; the tables for passive air cooled steady-state wires state something like 0.5-1" diameter, give or take depending on the details - way too heavy and cumbersome.

I don't know what sort of coolant they use, but I would expect that it is relatively nonconductive and non-flammable.

[ Parent ]

• and your #1 point(0+ / 0-)

is spot on. I think I tried to say something similar somewhere here in the comments.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• When I say DC line losses, I am referring to (0+ / 0-)

I^2R (read I Squared X R) losses.  The conductor has a known  resistance per 1000 meters or per mile, and when current flows in the conductor, voltage is dropped per ohm's law.  And voltage is dropped in the return line because the same current must flow in all parts of the circuit.  Given that I am not fully schooled in high voltage transmission, DC or AC, and likely never will be, I will leave it up to the IEEE to work through these issues and come up with "the real answer".  I'm not confident that this will be found in my lifetime since even with Grounding, that topic has been being fought out for over 120 years, is not fully settled.  A facinating disucssion on this topic can be found in the "Soare's book on grounding", available, if I remember correctly, from the NFPA (National Fire Protection Association).

Republicans are like alligators. All mouth and no ears.

[ Parent ]

• I thought DC was slightly more efficient(1+ / 0-)
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Ohiodem1

because there is no skin effect like you have in AC. Same I^2R losses.

But, again, I'm not a high voltage guy.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• It is. (1+ / 0-)
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Ohiodem1

And there's a number of other factors that make DC more efficient, too.  There's only one case where AC wins out on (ionization of the air around the wires), but it's a relatively small effect overall.

[ Parent ]

• I read it on Wikipedia, it must be true(1+ / 0-)
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Ohiodem1
Even though HVDC conversion equipment at the terminal stations is costly, overall savings in capital cost may arise because of significantly reduced transmission line costs over long distance routes. HVDC needs fewer conductors than an AC line, as there is no need to support three phases. Also, thinner conductors can be used since HVDC does not suffer from the skin effect. These factors can lead to large reductions in transmission line cost for a long distance HVDC scheme.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• High voltage current flows outside the line(0+ / 0-)

Outside the line EMF's are generated which can be harmful to living things.

The following information was in response to a question trying to determine the possibility of power lines running through inhabited areas to cause cancer.

Typically in the kiloamp range for transmission, usually hundreds of amps for distribution (lower voltage) (I have studied and worked with HV transmission line protection systems)

In my city the electrical network works like this: long distance transmission at 132kV. Sub transmission (around and between large cities) at 66kv or 33kV. Then distribution at 11kV and finally 415V for ordinary consumers.

Assume the insulated crossarms did allow wind generated electrical power to be carried longer distances with less loss by uping the voltage, what
would be the limit before health concerns became a factor and where would this occur?

Near substations?
Near transformers?

My suburb is supplied by a substation with two transformers which I know for a fact are both 50MVA capacity. This subtation is supplied from a 66kV line. So it is easy to find the maximum current: 50M/66K = 757 amps in one transformer, probably twice this, so 1514 amps at peak times with both running full capacity (wich is realistic, the elctricity company want to put an extra transformer in because the load is so high!).
In distribution lines?
Also, the distrubution voltage is stepped down from 11kV to 415 V by quite large transformers, usually about 250KVA range (different in the US, where you tend to have a larger number of smaller transformers, connected to one or two houses. Over here, one transformer might power about 50 to 100 homes). So at 11KV, the maximum current could be about 30 amps for each transfomer, a distribution line might power 10 transformers, so we are looking at 300 amps there, or at least in that order of magnitude.
Suppose 1514 amps per transformer at peak times now is doubled or tripled  in lines running on the insulated cross arms, what happens to the EMF and conductor heating?
So typical values are hundreds to thousands of amps. Higher currents are impractical because of conductor heating. Lower currents under utilize the capacity of the conductors. So a good round number might be 1 kiloamp for a HV transmission line (in each conductor!) and maybe 500 amps for some low voltage distribution.
Is there an upper limit to how much the lines can heat up before they enter a plastic range and fail in deflection?

Live Free or Die --- Investigate, Incarcerate

[ Parent ]

• How much would it help our economy?(31+ / 0-)

How many green jobs can we create? How much more installed wind capacity can this system deliver?

Think of it not as a cost, but as an investment.

"Political ends as sad remains will die." - YES 'And You and I' ; -8.88, -9.54

[ Parent ]

• Further to US Blues comment(21+ / 0-)

below (think of it as investment) there are other pure dollar and cents benefits.

If the resistance to wind damge is improved this is a pure dollar saving for the utility over the life-span (decades) of the transission line.

If the load bearing capacity is increased, with associated reduction in line losses, this is a direct benefit to the utility - aids in load balancing, aids in keeping low the installed base of older power generating facilities.

Oh, yes, and the wind power generation tie-in as icing (thick) on the cake.

• even if(4+ / 0-)

Even if they just start doing all replacements and new lines in this manner it could still start to see some big dividends fairly quickly.  If it saves money the way you say, no reason not to do it.

I wonder how much metal is tied up in those crossbeams?  And what exactly is the insulator material?  Plastic?

• wonder if they could put a windmill(2+ / 0-)
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artmartin, flitedocnm

on each of those towers?  certainly already high in the sky, so putting one on the tip of that point could save on construction costs, and they'd already be on the line carrying the current, so no loss there.

• Heck no(9+ / 0-)

You'd have to size the blades to avoid hitting the lines, in all wind directions. That means they'd be so small it would hardly be worth the effort.

Wind power works best when we utilize economies of scale: in other words, make 'em big.

We are all in the same boat on a stormy sea, and we owe each other a terrible loyalty. -- G.K. Chesterton

[ Parent ]

• However, couldn't they be big enough...(2+ / 0-)
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BlackSheep1, loftT

to account for power loss?  Improving each section to zero or even slightly less than zero loss?  Smaller windmills may be more economical to manufacture with cheaper materials, cheaper delivery and could be installed at the same time as the insulated crossarms.

I am not saying for sure it would work but I do not think askyron's question should be so readily dismissed.

"Perhaps the sentiments contained in the following pages, are not YET sufficiently fashionable to procure them general favour..."

[ Parent ]

• It's more complicated(4+ / 0-)
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KenBee, docmidwest, Hayate Yagami, loftT

Most wind turbines generate DC, not AC and to convert the ouptut to the kiloVolt or megaVolt levels on the lines and do it at each tower would be extremely expensive.  The scheme would also introduce more maintenance problems - just maintaining the lines themselves is already complex and dangerous.

The blades on a typical wind turbine are about 200 feet long (from the hub - radius).

Modern revolutions have succeeded because of solidarity, not force.

[ Parent ]

• I remember when...(2+ / 0-)
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I was in an electronics technology class back in the early eighties and had an older teacher who said that we would never have a stereo television signal.  He said that there were too many issues to overcome.

I am sure he meant what he said and believed it.  He was extremely intelligent and knew electronics (of the day) inside and out but did not have the forsight to see beyond his understanding of technology.

I am sure you know a lot more than I do on this and I am not arguing that it is a valid or efficient solution to anything but...  I have found that it is easier to dismiss an idea that sounds different or too easy or simple than to try to come up with new ideas that work.  How many people would have viscerally rejected the idea of insulated cross arms without ever really giving the idea a chance?  I bet this wasn't the first time it was proposed.

"Perhaps the sentiments contained in the following pages, are not YET sufficiently fashionable to procure them general favour..."

[ Parent ]

• was that the 1880s?(2+ / 0-)
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sorry, just poking fun. Multichannel TV sound was developed in the 70s and adopted by the FCC in 1984.

The primary issue is that the voltage levels are vastly different. output of a small wind turbine is typically in the hundreds of volts. T-lines are in the hundreds of thousands of volts.

It's a great idea on distribution systems, electrified railways, etc. I just don't think it is feasible in the foreseeable future on t-lines.

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[ Parent ]

• It's entirely possible to do(1+ / 0-)
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Hayate Yagami

It's just not economically feasible or worthwhile with current technology. Anything's possible in the future, as you point out, but it would seem to me that if we had technology to make this feasible, we would be so advanced in our energy technology it would no longer be necessary.

Stereo sound on even a standard analog TV signal wouldn't have been hard to do in the 1960s - not that much different that stereo FM radio (TV sound is AM, but the same principle - multiplexing - could be applied)

Modern revolutions have succeeded because of solidarity, not force.

[ Parent ]

• I don't know why...(0+ / 0-)

Mr. Kendell believed the way he did.  It was 1983 and he was in his 60's.  He taught us basic electricity and transistor logic.  He was (from my prospective at the time) big and old and mean.  He was unable to use his right hand for some reason and it was tensed and curled up and would twitch fairly violently at all times.  We would laugh at anyone who got caught at the urinal when he would come in because he would stand next to you and that twitching hand would repeatedly bump into you.  That is how I remember Mr. Kendell and I remember him telling me there would never be stereo television.  I did not believe it even then but he was adament for whatever reason.

The point was that people believe something for good reason or not and they seldom consider obvious or simple solutions later because they see easy, "insurmountable" problems and dismiss ideas before looking at them critically and trying to see if they can work or lead to something new.

It is human nature and not an indictment against you.  Ideas that were once considered cost prohibitive remain cost prohibitive in thought even after new technology or production methods reduce that cost considerably.  The mind says, "I have already considered that and it does not work so I will not consider it again".

I am what some people would call a professional problem solver.  I teach people how to solve problems in manufacturing settings.  You would be amazed at how often good ideas are dismissed as impossible, "we have already tried that", "it won't work because X,Y and Z".  These are intelligent people who are experts in their field.  They hate when guys like me come in and point to an obvious solution and then, after they fight it tooth and nail, prove that the idea works.  They are not stupid people.  Usually, they had tried it before and for whatever reason, it didn't work so they dismissed it and never tried it again.

I am not arguing that the idea will work.  However, I do know that the top of these huge towers are underutilized space and there are advantages in green power for unrestricted access to wind and sunlight.  I also know that if a major project is being planned, such as replacing the existing cross arms with insulated ones, it would be cheaper to combine any additional projects together to minimize labor, equipment and downtime.

I bet that if someone like you, who is a lot smarter than me about these kinds of things, put their mind to thinking of someway to better utilize those advantageous aspects of the towers, you could come up with something that would be cost effective and worthwhile.  I usually think something is impossible before I figure out a way to solve it.  It makes it more exciting and rewarding that way.

"Perhaps the sentiments contained in the following pages, are not YET sufficiently fashionable to procure them general favour..."

[ Parent ]

• Keith Pickering: for the "new hotness" but really(9+ / 0-)

they work fine in sizes from 6 ft to 10 ft if you're generating power per user -- if we all had windmills in our backyards, as used to be common on Plains farms from Texas to Alberta, and from Iowa to Oregon, we wouldn't need these big towers or these long lines. Our national power system would be, in some ways, far more robust.

It's harder for e.g. a terrorist (or a tree branch) to take out all the power in five states if that power's not centrally generated and then parceled out over non-hardened lines.

("Hardened" power generation means keeping the means of sending the power out of harm's way. The simplest means is burying the lines, but as IT folks know, this makes you subject to the ravages of the fiber-seeking backhoe.)

REA and Co-op lights changed the world. Now, the big power companies have changed it again. Maybe one of the things we need to do, going forward, is to change it still another time -- from big, central, corporate controlled vulnerable coal / gas / oil-fired plants to wind and solar "off the grid" sources sized for homes / city blocks / neighborhoods.

LBJ, Lady Bird, Anne Richards, Barbara Jordan, Sully Sullenberger, Ike, Drew Brees, Molly Ivins --Texas is no Bush league! -7.50,-5.59

[ Parent ]

• I was thinking of something like(1+ / 0-)
Recommended by:
Nina Katarina

Verticle wind turbine
No overhang, weight centralized, power output reasonable to scale

• Civil/Mechanical Considerations Might Dominate(1+ / 0-)
Recommended by:
Hayate Yagami

Putting a wind turbine system on the top of transmission tower will exert considerable rotation moment on the base of the tower, trying to topple it over.  The tower design would have to be considerably modified to enable the tower to resist those forces, which makes it less than a zero-cost option from the transmission engineers viewpoint.  Further, the wind generators would not be producing power at the same voltage as was being transmitted on the tower, so transformers would need to be mounted on each tower to boost the generated voltage to equal the transmission voltage.  It would seem that everything done to adapt the wind generator increases mass at the position on the tower which exerts the most moment on the tower.

"Love the Truth, defend the Truth, speak the Truth, and hear the Truth" - Jan Hus, d.1415 CE

[ Parent ]

• Also, if one broke(0+ / 0-)

it could shear line lines. Ewww.

"What could BPossibly go wrong??" -RLMiller "God is just pretend." - eru

[ Parent ]

• not readily. the tower that holds(1+ / 0-)
Recommended by:
Lujane

the generator has to bear different sorts of loads than the towers that carry the lines.

LBJ, Lady Bird, Anne Richards, Barbara Jordan, Sully Sullenberger, Ike, Drew Brees, Molly Ivins --Texas is no Bush league! -7.50,-5.59

[ Parent ]

• not really(1+ / 0-)
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PrahaPartizan

for the reasons that Keith Pickering said, but, more importantly in my mind is the voltage mismatch. It takes a BFT (Big [REDACTED] Transformer(R) to get up to the voltage of a transmission line. You wouldn't be able to just plug the wind turbine directly into the line.

You can on buildings, street lights, and maybe distribution lines, but not t-lines.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• Less burning, because less power loss(0+ / 0-)

That's the most intuitive way I can think of to explain it.

• Voltage_current(2+ / 0-)
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At 2.5 x voltage, 2.5 x power at the SAME current.

• If you read(0+ / 0-)

this pdf - and it's especially clear at the bottom of page 6 - the existing lines are not appropriate for high voltage transmission - e.g., the 745 kV transmission mode that is the most efficient.

the article in this diary only dealt with up to 400 kV, or about half this level (which is considerably less efficient, you really need to go up to 745 kV for the magic to kick in . . .. ).

• Page 6?(2+ / 0-)
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There's nothing on page 6 that is germane. Typo?

Not sure what you mean by "the existing lines are not appropriate for high voltage transmission". If you look at the chart on page 4 of your document, you will see that 230 kV, 345 kV, and 765 kV all use the exact same cable: ACSR 954 mcm. They just use a different number per phase.

The point of the article linked to in the diary is that existing towers could be retrofitted to carry more power at a higher voltage. Using traditional technology, you would have to tear out the tower and build new to step up to a higher voltage.

Javelin, Jockey details, all posts, discontinue

[ Parent ]

• Yes, sorry, that must have been a typo(1+ / 0-)
Recommended by:
jam

but on page 4 the table shows that the 765 kV line (I must be higly dyslexic today - since that's where the 4 went I needed for the page number - into the 745 kV I stated earlier, ugh!) requires a "4 conductor bundle"  (and the newer, more efficient designs use a "6 conductor bundle) whereas lower voltages use a "2 conductor bundle"

So, maybe the cable is the same in all cases, but it seems to have to be configured differently to move the super high voltages . . .

• Did they look at insulation?(2+ / 0-)
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