DC transmission cost

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K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
A European breed........so there!
:p

Born in the USA. So there. (My apologies to the Bruce Man.)

I am also a 'European breed' born in the USA. I'm Irish.

Our city throws a big Irish festival every year. There's Irish music, Irish food, Irish beer, Irish dancing and people dress in Irish attire. I got some free tickets to go one year.

Now I know why my family left Ireland.
 

Besoeker

Senior Member
Location
UK
110606-2054 EDT

The goal of my original post was to get some rough idea on costs. There are many individuals that make claims that DC transmission is very expensive and good for only single source and single destination operation, and not over short distances. The very expensive part is what I want to know about. I can intuitively agree with the two point and long distance part of their statements. Does it cost $0.001/KWH for transmission , or $0.01, or $0.10?
Back on topic....if, as I have seen claimed, transmission losses are 3% per 1000km wouldn't that make the cost 3% unit per 1000km?
You can't give a fixed figure of say $0.01 per kWh. Surely it has to be pro-rata with transmission distance?
Added to that are the losses associated with the step up transformers and converter at the sending end and the inverters ans transformers at the receiving end.
My direct experience on conversion and mains commutated inversion is limited to about 5kVdc but generally we would expect efficiencies to be 98% or above. That's say, another 4% for conversion and inversion regardless of transmission distance. And about the same again for the transformers at each end, also not related to transmission distance.
I hope that goes some way to answering your question.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I don't know if you guys realize the Pacific coast intertie operates at 500k. Wow!
I was told by a DWP utility engineer that in the early days when maintenence would wash down the insulators at the towers if the water truck let the stream follow the tower to the ground they would get quite a fireworks show.
In order to cobat this a special truck was designed that pulsed the water instead of a steady stream.

just a little tidbit,
 

Besoeker

Senior Member
Location
UK
I don't know if you guys realize the Pacific coast intertie operates at 500k. Wow!
Worldwide, there are a number operating at that voltage level and a few at higher voltages - some at 800kV.
I was told by a DWP utility engineer that in the early days when maintenence would wash down the insulators at the towers if the water truck let the stream follow the tower to the ground they would get quite a fireworks show.
In order to cobat this a special truck was designed that pulsed the water instead of a steady stream.
That I didn't know. But interesting.

just a little tidbit,[/QUOTE]
 

Electric-Light

Senior Member
The pacific Coast intertie runs from near The Dalles Oregon to Southern California.
If your driving around the east side of the Sierras AS in going from LA to Death Valley you will drive under it. A two line system not a multiple of 3 as most transmission systems are.

http://en.wikipedia.org/wiki/Pacific_DC_Intertie

The economics are good but I don't have all the numbers.
A big factor is the losses in the electric field. IF you stand under a 345 line sometimes you can hear the buzz. That buzz is power being dissappated into the air. The higher the voltage the greater the loss. Building and reversing that magnetic field around a transmission line can eat up a lot of power.

The inverters and converters limit the power that can be transmitted. If the power gird of Southern California were connected to The northwest grid it could in theory draw all the power out of the northwest. As lights went on in LA they would go dim in Wenatchee and Portland.
The inverter station at Sylmar acts like a 3,100 MW generator. When it reaches 3,100 MW output that's it, it can't suck more by drawing down the voltage.

They are used because they are more efficient and can limit the power transmitted.
There are a couple out of North Dakota (where there is lots of power ) over to Minnesota.
There are more out there and will be even more as windfarms are built in the Flyover Zone.
Google is your friend, look for "HVDC";)

Speaking of hydro and wind, BPA is in midst of political mud puddle right now since the hydroelectric power can produce more than we can use so they say right now.

Maybe they can just cut the power rate in half for a while, encourage people to air condition to 72 degrees around the clock, leave their computers on 24/7, and encourage the use of high wattage incandescent light bulbs :)
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I don't know if you guys realize the Pacific coast intertie operates at 500k. Wow!
I was told by a DWP utility engineer that in the early days when maintenence would wash down the insulators at the towers if the water truck let the stream follow the tower to the ground they would get quite a fireworks show.
In order to cobat this a special truck was designed that pulsed the water instead of a steady stream.

just a little tidbit,

So, why doesn't that happen when it rains?
 

Besoeker

Senior Member
Location
UK
Born in the USA. So there. (My apologies to the Bruce Man.)

I am also a 'European breed' born in the USA. I'm Irish.

Our city throws a big Irish festival every year. There's Irish music, Irish food, Irish beer, Irish dancing and people dress in Irish attire. I got some free tickets to go one year.

Now I know why my family left Ireland.
It always surprises me how many Americans claim to be Irish or of Irish descent. I looked into that a little while ago, maybe around the time of St Patrick's day celebrations. Many more Americans make the claim than the entire population of Ireland.

Many Brits might find that a bit odd. The Irish tend to be the butt of jokes of the Scotsman, Englishman, and an Irishman type. I think it's along similar lines to the jibes about the Polish in the US. I have heard that the Swedes joke about the Norwegians in the same way. Stereotyping isn't something I buy into - but it happens.
 

mivey

Senior Member
Indeed. It also rains in the lakes and rivers.
Around here too.

At any rate, the powerline washers don't wash in a solid stream of water. There are water droplets mixed with air that create resistance. They also use water of varying types depending on the voltage level.

Any arcing that a DPW worker saw was probably due to contamination on the insulators in combination with the water. It is possible to get a flashover and to draw arcs but that would never be from the insulator to the ground as the distance is just too far to create a solid stream of water.

These washing tools have monitors that measure the resistance of the water and there are minimum distances, nozzle sizes, and water resistivity that they follow for difference voltages and washing techniques..
 

mivey

Senior Member
Didn't myth busters bust the myth about urinating on third rail causing electrocution?
Yes. The water formed droplets and so they did not have a solid stream.

And, uh.....just how did they prove whatever they proved?
Collected urine, mounted a bladder on a fake person, hooked up the meters, energized the substitute rail, then opened a valve to simulate the flow. I guarantee you would get shocked if you got close enough. The next time you are out hunting and find a suitable fence, try your luck.
 
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Besoeker

Senior Member
Location
UK
110611-0847 EDT

Following is a good article that in part provides a partial answer to my original post. It does not provide a cost per KWH, but provides break-even information between AC and DC transmission as a function power and line length.

The kWh loss is a power and line length. And time of course.
Here's an article suggesting 3% per 1000 km.

http://www.sindark.com/2008/01/07/hvdc-transmission-for-renewable-energy/

This the same loss as I gave in post #2 but from a different source.
Take, for example, the India - Talcher, Orissa transmission system. It's 1450 km long and rated at 2000MW. At 3% losses, total loss at full rating is thus 87MW.
This works out at about 97kW per mile for a 2000MW system running at 2000MW.

That any help?
 

Electric-Light

Senior Member
The kWh loss is a power and line length. And time of course.
Here's an article suggesting 3% per 1000 km.

http://www.sindark.com/2008/01/07/hvdc-transmission-for-renewable-energy/

This the same loss as I gave in post #2 but from a different source.
Take, for example, the India - Talcher, Orissa transmission system. It's 1450 km long and rated at 2000MW. At 3% losses, total loss at full rating is thus 87MW.
This works out at about 97kW per mile for a 2000MW system running at 2000MW.

That any help?

That looks pretty similar to the pacific intertie system, which is 1MV +/-500kV also. The Oregon side station dumped ASEA(now ABB) mercury valves which used hundreds of kilos of mercury. I think they're using ABB solid state system now.
 

BJ Conner

Senior Member
Location
97006
Hydrogen next?

Hydrogen next?

The figures here are just for purposes of amusement. A more detailed analysis would require more accurate information

The Pacific Intertie is 846 miles long. Assume it looses 100 KW/mile.
100 KW/mile x 842 miles =84.6 Megawatts
84.6 megawatts x 24 hrs = 2,030.4 MHs/day.
At $50/MW Hr that is $ 101,520/day or $37,054,800 /year.

The next step when your bring power from say the wind belts of the western Dakotas to civilization is to conver the power to hydrogen and put in a pipeline.
Pipelines are the most efficient means to transport energy.
Lots of problems with this most solvable and there are people working on them.
 

Besoeker

Senior Member
Location
UK
That looks pretty similar to the pacific intertie system, which is 1MV +/-500kV also. The Oregon side station dumped ASEA(now ABB) mercury valves which used hundreds of kilos of mercury. I think they're using ABB solid state system now.

The old mercury arc rectifier....or, as my late, great friend Tommy used to call them, mercury archaic rectifiers.

Yes, solid state. I have only seen one mercury arc rectifier in operation and that was over 30 years ago. Just before we installed a thyristor replacement.

Many HVDC transmission systems are thyristor (SCR) based these days and IGBTs are being increasingly used.
 

Electric-Light

Senior Member
The old mercury arc rectifier....or, as my late, great friend Tommy used to call them, mercury archaic rectifiers.

Yes, solid state. I have only seen one mercury arc rectifier in operation and that was over 30 years ago. Just before we installed a thyristor replacement.

Many HVDC transmission systems are thyristor (SCR) based these days and IGBTs are being increasingly used.

I got to tour that place when mercury arc rectifiers were still in use. It was pretty cool. I love facility tours :) At the time, some were already solid state and i was explained they have redundancy built in, so failure of some hockey puck power semiconductor parts won't down the system. Because of the high voltage and noise involved, the triggering isn't done electrically, but optically.

How do solid state systems compare to mercury arc valves in term of efficiency?
 

Besoeker

Senior Member
Location
UK
I got to tour that place when mercury arc rectifiers were still in use. It was pretty cool. I love facility tours :) At the time, some were already solid state and i was explained they have redundancy built in, so failure of some hockey puck power semiconductor parts won't down the system. Because of the high voltage and noise involved, the triggering isn't done electrically, but optically.
A link here:
http://www.ewh.ieee.org/r8/germany/ias-pels/m_berlin/siemens/lips_high_power_direct_light_triggered_thyristor_valve_techn.pdf

How do solid state systems compare to mercury arc valves in term of efficiency?
TBH, I don't know. I would expect a thyristor (SCR) to have a forward voltage of around 2V in normal operation. That I can calculate that fairly accurately from the application and the published datasheets.
I have a vague recollection that the forward voltage on a mercury arc rectifier is some tens of volts and, on that basis, their losses would be about an order of magnitude greater than more modern solid state systems.
 
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