DC transmission cost

[gar]

110613-2116 EDT

One reference I found indicated the anode cathode arc drop for a thyratron was about 15 to 20 V. I did not look at any old data sheets. The thyratron is more limited in cathode current than a mercury-pool or Ignitron is. Some Ignitrons have a PIV capability of 20,000 V and the possibility of 1000 to 10,000 amperes.

An SCR with a lower PIV rating is going to beat the mercury devices in efficiency and ease of control.

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[gar]

110613-2138 EDT

B J Conner:

Your suggestion of hydrogen transport thru pipe lines is interesting. Do you have specific information on the energy input to pumps relative to the amount of energy transported by hydrogen thru a 1000 mile pipe?

Even if this is vastly less than the the efficiency of electric current thru 1000 miles of copper wire it is not the whole transport cost. The generation of hydrogen from electrical energy is very inefficient. On the order of:

From http://en.wikipedia.org/wiki/Fuel_cell under "In Practice"

Fuel cells cannot store energy like a battery, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power, they are combined with electrolyzers and storage systems to form an energy storage system. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency) is between 30 and 50%, depending on conditions.[38] While a much cheaper lead-acid battery might return about 90%, the electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore better suited for long-term storage.

However, if energy storage is part of what is required, then hydrogen may be useful. But keep in mind that pumped storage is about 80% efficient for input to output.

The inefficiencies of solid-state voltage converters is much less than than electric to hydrogen to electric energy conversion.

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[Electric-Light]

I read somewhere that some of the largest single gas "customers" are the utility's own pipeline compressor stations which are self-powered using the natural gas in the pipeline using natural gas engine(s).

 

[Electric-Light]

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


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.

it looks like they're stacked in series. 2v EACH right? Do you connect as many mercury arc valves in series as you do SCRs per string?

 

[Besoeker]

I read somewhere that some of the largest single gas "customers" are the utility's own pipeline compressor stations which are self-powered using the natural gas in the pipeline using natural gas engine(s).

Could be so. We have produced a few variable speed drives for them in the several MW range. The run as duty/standby with gas compressors as the main drive.

 

[Besoeker]

it looks like they're stacked in series. 2v EACH right? Do you connect as many mercury arc valves in series as you do SCRs per string?

The 2V is the forward voltage when conducting. The blocking voltage of modern SCRs is up to several kV. The highest I've used is 6.5kV but I think they are available up to at least 8kV.

I don't how mercury arc rectifiers are connected in series. The only configuration I've seen was hexaphase with a common cathode.

 

[boxs21]

the pump storage is largest in eroupe.:happyno::happysad:

 

[Electric-Light]

The Pacific intertie is +/- 500kV. That IEEE article even shows diagram with multiple optically triggered hockey pucks in series. There are probably more in stack than needed and bypassed so that failed puck can be bypassed.

I expect the entire stack to have a drop far far far more than 2v.

 

[Besoeker]

The Pacific intertie is +/- 500kV. That IEEE article even shows diagram with multiple optically triggered hockey pucks in series. There are probably more in stack than needed and bypassed so that failed puck can be bypassed.

I expect the entire stack to have a drop far far far more than 2v.

I would expect a thyristor (SCR) to have a forward voltage of around 2V in normal operation.
So yes, of course, a limb of a system with many in series would have multiple times that on HVDC conversion/inversion circuits.

But the multiples of 2V need to be seen in the context of the DC transmission voltage. At around 5kV, we used four devices in series per limb and, for each three-phase rectifier, you have two limbs in series at any one point in the cycle. So, about 16V drop in 5kV. That's the major source of losses. Snubbers and suppression circuits add considerably to that. I don't know how those are implemented on HVDC systems.

A quick back of the envelope calc....
Suppose you have a 500kV DC rectifier system
Conventional practice is that the rated blocking voltage for the devices used is about three times the AC supply voltage which is usually lower than DC voltage. But ignoring that, go for three times the DC. So 1,500,000 V blocking voltage would be required. At 8,000V each, that would require a total of about 190 devices per limb. Or 380 in series.
So 760 Volts drop.
Sounds huge to us mere mortals.
But in the context of 500,000V.......

Add 50% redundancy and you get 1,140 V drop.

But is the 2V per device valid? Probably so.
Infineon, for example, have an 8kV device where the on-state characteristic is 2V at 3,000A.

 

[Electric-Light]

So, overall power dissipation in valve halls in SCRs vs mercury arc ?

 

[gar]

110616-1705 EDT

I found one reference relative to Ignitrons that per tube were capable 20,000 or near there for working voltage, and thousands of amperes. These would have voltage drops of 15 to 20 V, maybe more at very high currents. Thyratrons are in the same voltage drop range if using mercury. If a gas type maybe 100 V.

If an SCR can work at 5000 V and a 2 V drop it is a clear winner on voltage drop and power loss.

But other factors are important. How do you trigger an Ignitron? Not easily. An SCR is easy to trigger even at a large elevated voltage. What are suitable actual working voltages for an SCR, Ignitron, or Thyratron in a high reliability application? I do not know, but probably lower than the 20,000 or 5000 I mentioned above.

Besoeker's comments for SCR working voltage are probably in the correct range.

.

 

[Besoeker]

Besoeker's comments for SCR working voltage are probably in the correct range.

Thank you kindly.
Power electronics is my niche.

 

[Open Neutral]

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.

I'm laughing my head off on this. I've worked in the petroleum products pipeline business, and it's a major PITA to build and maintain such vs say a 345KV line.

And piping hydrogen around boggles my mind. One of the major issues with the Apollo 2nd & 3rd stages was their J2 engines burned hydrogen, not kerosene. McDonnell Douglas went though absolute hell for years trying to keep keep the fuel system intact; hydrogen leaks though anything.

I can not see how you could build a 500-100 mile cryogenic line for such.

 

[tallgirl]

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.

Because the English were fond of oppressing the heck out of the Irish and many Irish men and women left for the States in the 19th and 20th centuries.

 

[Besoeker]

Because the English were fond of oppressing the heck out of the Irish

Funny lot, the English. Glad I'm not one of them....

and many Irish men and women left for the States in the 19th and 20th centuries.

According to Wikipedia, over 36 million Americans claim Irish ancestry. The entire population of Ireland is less than 5 million.
Don't these figures strike you as a bit odd?

 

[BJ Conner]

Yep there are problems

Yep there are problems

I'm laughing my head off on this. I've worked in the petroleum products pipeline business, and it's a major PITA to build and maintain such vs say a 345KV line.

And piping hydrogen around boggles my mind. One of the major issues with the Apollo 2nd & 3rd stages was their J2 engines burned hydrogen, not kerosene. McDonnell Douglas went though absolute hell for years trying to keep keep the fuel system intact; hydrogen leaks though anything.

I can not see how you could build a 500-100 mile cryogenic line for such.

IF you wanted to take enought power out of the mid west topower the east coast it would be no problem. A swath of 500 KV transmission lines about 3 or 4 miles wide would work. If we're going to limit our future by the technology of the past, let's go back to the 19 th century. Things were much better then (or were they?)
Hydrogen make sense because fuel cells exist that can be placed in distribution substations. The 12 KV ( or 4.16 or 34 etc) distributions systems would not need to be changed.

 

[K8MHZ]

Funny lot, the English. Glad I'm not one of them....


According to Wikipedia, over 36 million Americans claim Irish ancestry. The entire population of Ireland is less than 5 million.
Don't these figures strike you as a bit odd?

Not really. Let's do the math. One family leaves Ireland (-6) and comes to America (+6) and over generations can add hundreds to the American side of the equation (+100(s).

Look at how many people can claim Spanish ancestry vs. the entire population of Spain.

 

[K8MHZ]

hydrogen leaks though anything.

Even metal.

 

[Besoeker]

Not really. Let's do the math. One family leaves Ireland (-6) and comes to America (+6) and over generations can add hundreds to the American side of the equation (+100(s).

OK.
Let's look at the maths.
The population decrease in Ireland owing to famine and emigration in the mid 1800s is estimated at about 2,000,000. But suppose none died of starvation* and all 2 million emigrated to America. And that none died during the crossing**.
So around 1850, you get an influx of Irish people.
At current the current population growth rate, that would result in the 2 million increasing to about 9.8 million.
Yes, I accept that the birth rate was probably higher then. But life expectancy was shorter. China, as I'm sure you know, has a one child per couple rule. You'd think that would result in a population decline. But it is still increasing. People are living longer. Birth rate alone is not a sufficient indicator of population growth rate.

*Some did die of starvation.
**Many did not survive the passage. The ships were dubbed by some as "coffin ships".