4 Wire Wye Vs 4 Wire Delta - New Construction

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mbrooke said:
...Biggest drive behind DC will be renewable energy.
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Following is unsubstantiated personal opinion or possibly marginally substantiated by anecdotal account. Recommend: Strongly consider deleting before reading.

I'm not there yet either. As far as I can tell the only thing that makes any renewable cost effective is the government subsidy. There are only small, specialized markets where any renewable is cost effective as a stand alone. Renewable is not going to drive widespread DC distribution any further than the homeowners' property lines. And the subsidy will only drive it that far.

As for me and renewable: I'm working with my BIL in TX to milk the snot out of the Fed and TX subsidies, and guarenteed purchase by utility of excess power. Looking at both solar and wind. Got nothing to do with green. Has all to do with taking max advantage of the law. If Americans want to pass laws handing out money, I feel obligated as an American citizen to take as much as I legally can.

just an opinion of the worm
 
iceworm said:
Absolutely imagineable. I'm a little bit familiar with Rockwell's IGBT frontends on their MV drives. For 500A, six hockey puck sized semiconductors stacked up to make 6600V on each bridge leg. Add a water/glycol cooling system with an outside radiator, to keep them alive anytime the current is going through them. Two 3' x 3' x 6' cabinets for a 500A CB. hummmm......Concept is great, but consider a 1200A SF6 MV CB ~ 3' x 3' x 3'.

That is why I'm asking: Is anyone making DC CBs using different technology than that available in the 1880?

ice
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This:


http://new.abb.com/about/events/cigre2014/hvdc-breaker


http://new.abb.com/docs/default-source/default-document-library/hybrid-hvdc-breaker---an-innovation-breakthrough-for-reliable-hvdc-gridsnov2012finmc20121210_clean.pdf?sfvrsn=2
 
iceworm said:
Following is unsubstantiated personal opinion or possibly marginally substantiated by anecdotal account. Recommend: Strongly consider deleting before reading.

I'm not there yet either. As far as I can tell the only thing that makes any renewable cost effective is the government subsidy. There are only small, specialized markets where any renewable is cost effective as a stand alone. Renewable is not going to drive widespread DC distribution any further than the homeowners' property lines. And the subsidy will only drive it that far.

As for me and renewable: I'm working with my BIL in TX to milk the snot out of the Fed and TX subsidies, and guarenteed purchase by utility of excess power. Looking at both solar and wind. Got nothing to do with green. Has all to do with taking max advantage of the law. If Americans want to pass laws handing out money, I feel obligated as an American citizen to take as much as I legally can.

just an opinion of the worm
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Its growing none the less. But three major problems (among others) occur. Wind, solar ect in bulk tend to be generated far away and spread apart from major load centers. The lengths required make AC lines to lossy and in some cases physically impractical such as an AC line from Nevada to New York State or an underground cable spanning states. The reactive AC losses (charging currents) exceed the amount of power to be transmitted. In fact its said an AC line from California to Maine would just radiate off into space. The only solution is DC which has no running losses other then I2R and some cornoa. Skin effect, inductance, capacitance, ect are not a DC concern.

Second interconnecting grids is a double edge sword. While power resources increase, reliability and stability actually becomes a challenge. In a DC system linking to or more AC systems, the AC pockets can each have their own frequency. Events like voltage collapse are far less likely to spread and DC converters provide superior load flow control. DC does not care about phase angle, frequency, rotor angle stability, oscillation, reactive resources, and other requirements only a concern in DC. You have to keep in mind that while induction is preferred for transformers and motors, they are unwelcome on transmission lines. We just put up with them because DC is not yet entirely practical at present day.


Third is the fact a home with solar panels can either generate power or consume it, something unheard of on a mass scale. For one typical protective relaying (recloser, fuse) can not comprehend that requiring the re-thinking of protective relaying. Advanced relaying is possible with AC, but Ive heard its easier for DC.




ggunn said:
DC transformers?
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This post:

http://forums.mikeholt.com/showthread.php?t=173330&page=5&p=1693738#post1693738
 
Not particularly pertinent, just a knowledge issue:

Length of AC transmission lines:
As I recall from a 400 level transmission class, mid 80's, AC lines loose stability around 600 miles. The example we studied was James Bay Hydro connection to US grid to feed NYC. There is a back-to back DC link at the Canada-US border. Solves the stability problem of interconnecting two AC grids.

ice
 
mbrooke said:
...Third is the fact a home with solar panels can either generate power or consume it, something unheard of on a mass scale. For one typical protective relaying (recloser, fuse) can not comprehend that requiring the re-thinking of protective relaying. Advanced relaying is possible with AC, but Ive heard its easier for DC.
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This completely loses me. Where are you going with this?


ice
 
mbrooke said:
This post:

http://forums.mikeholt.com/showthread.php?t=173330&page=5&p=1693738#post1693738
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That's DC to DC conversion, not a DC transformer. There is AC and a transformer at the heart of it.

Unless someone comes up with a way to use all the existing infrastructure and convert all the generation and consumption hardware to DC, I don't see a conversion to DC anytime real soon. And it sounds expensive; who's going to pay for it? We can't even seem to justify the expense of keeping our roadways in usable condition despite the fact that bridges are literally collapsing.
 
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I absolutely agree the industry is advancing - New concepts, developing new sources, yes technology advances. And yes, we have advanced beyond the 1880s mag circuit/puffer CBs. And yes we have advanced beyond the mercury pool inverters of the 1930s.

However, ABB's "New" HVDC CB is still in R&D. Maybe they will eventually get to where one can be installed to tap an HVDC line at every hamlet the transmission passes - nowhere near there yet.

As for the renewables: Compare all the residential renewable sources, $/KW, with one mediocre fossil fuel plant. Nope, no money there.

As long as I am dreaming, the renewables need a breakthrough in energy storage - say a new battery with 10x - 100x energy density (hey, I'm dreaming - remember). That will do a lot to making the renewables cost effective. But I still don't see the distribution to end users being DC.

For general energy production, my crystal ball (and it is really cloudy) is saying 'fusion, and maybe even cold fusion'. Maybe by then there will be a workable DC CB allowing small taps on an HVDC transmission line, going to a local AC substation. 50 years ago this was science fiction. Today - its R&D, and 50 years from now - ?? Don't know.

Nothing against anything you are saying. These are just my flights of fantasy.

ice
 
ggunn said:
... I don't see a conversion to DC anytime real soon. And it sounds expensive; who's going to pay for it? ...
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I'm agreeing with you. Hopefully it will be the users/consumers. Which means it must be cost effective. Hopefully the world does not float with funny money (say government subsidies - for example)

ice
 
iceworm said:
I'm agreeing with you. Hopefully it will be the users/consumers. Which means it must be cost effective. Hopefully the world does not float with funny money (say government subsidies - for example)
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Personally, I see nothing wrong with well thought out and judiciously applied government subsidies which are paid for with existing revenue rather than borrowing more from China.
 
ggunn said:
That's DC to DC conversion, not a DC transformer. There is AC and a transformer at the heart of it.

Unless someone comes up with a way to use all the existing infrastructure and convert all the generation and consumption hardware to DC, I don't see a conversion to DC anytime real soon. And it sounds expensive; who's going to pay for it? We can't even seem to justify the expense of keeping our roadways in usable condition despite the fact that bridges are literally collapsing.
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In theory its not if we just call out the inductive part, however I can see these coming in single prepackaged units after refinement. Technically there is no such thing as an electronic transformer either, but that name is applied frequently:

http://www.st.com/web/en/resource/technical/document/application_note/CD00003902.pdf



Equipment will have to be replaced over time, as well as gradual but major changes to the transmission system even if we keep AC. Our Current grid is not only dated and under capacity but also not fully ready for large scale renewables.

Conversion will start from the top down by the looks of it. It will first take place as major Ultra high voltage links between generation and load pockets (as we see today), then moving to regional 500 and 345kv bulk transmission systems, down to local 138 and 115kv systems. It will proably stay like that for a bit until local 5-35kv class distribution lines go DC with the final process being utilization which imo will long have become at least partial DC in some places. The push for DC in utilization will only come from solar panels where maximum efficiency is obtained by bypassing inverters. Imagine feeding a 120 volt DC solar system into an ultra capacitor or super battery then being able to deliver that right to a receptacle, lighting circuit or directly out to the grid via simple protective device (separates system on loss of POCO) rather then energy wasting inverters.


In short, the power grid of tomorrow will allow all customers in all locations to add or deduct as much power as they like from the grid with minimal losses and exceptional reliability.
 
mbrooke said:
In short, the power grid of tomorrow will allow all customers in all locations to add or deduct as much power as they like from the grid with minimal losses and exceptional reliability.
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Sounds great but I don't see it happening any time soon. The current economic/political climate heavily favors the application of bandaids on the cheap and kicking the systemic challenges down the road to be Somebody Else's Problem.
 
mbrooke said:
... Third is the fact a home with solar panels can either generate power or consume it, something unheard of on a mass scale. For one typical protective relaying (recloser, fuse) can not comprehend that requiring the re-thinking of protective relaying. Advanced relaying is possible with AC, but Ive heard its easier for DC. ...
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iceworm said:
This completely loses me. Where are you going with this?
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mbrooke said:
You loose selective coordination under large co-generation customers.
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Nothing I know of or have heard of. Got some references? Generally speaking - degree of coordination is just a matter of money.

Following is not my area of expertise. Just guessing based on my understanding of the physics:
Not sure why DC would be easier (to coordinate)
For AC we have PTs and CTs

For DC, one would use Hall effect sensors and resistive voltage dividers. I don't know what is available for DC relays. I don't get beyond DC rated fuses and DC rated molded case CB's. Still, once one gets past the relay input A-D converters, the internals are just a digital PLC. Probably not much difference there.

Although there is one - Reverse power. That's a bit tricky (but certainly well understood by relay mfgs) for AC, and should be simpler DC - one has only to look at the voltage polarity and current direction.

Not seeing the issues - especially if the customers are "large". That means they have plenty of money to spend. As mentioned - that fixes most coordination issues.

ice
 
ggunn said:
Personally, I see nothing wrong with well thought out and judiciously applied government subsidies which are paid for with existing revenue rather than borrowing more from China.
Click to expand...

I don't mind government funded R&D that becomes public knowledge. Can't say the same for production subsidies. Skews the economics to where we get wind farms where the $/kw are a complete joke. And the joke is on us that pay the taxes.

I have a terrifying picture of a bureaucratic committee judiciously applying their well thought out strategy. (shudder) Quoting Ronald Reagan:
The most terrifying words in the English language are: I'm from the government and I'm here to help.

Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.​

ice
 
iceworm said:
Nothing I know of or have heard of. Got some references? Generally speaking - degree of coordination is just a matter of money.

Following is not my area of expertise. Just guessing based on my understanding of the physics:
Not sure why DC would be easier (to coordinate)
For AC we have PTs and CTs

For DC, one would use Hall effect sensors and resistive voltage dividers. I don't know what is available for DC relays. I don't get beyond DC rated fuses and DC rated molded case CB's. Still, once one gets past the relay input A-D converters, the internals are just a digital PLC. Probably not much difference there.

Although there is one - Reverse power. That's a bit tricky (but certainly well understood by relay mfgs) for AC, and should be simpler DC - one has only to look at the voltage polarity and current direction.

Not seeing the issues - especially if the customers are "large". That means they have plenty of money to spend. As mentioned - that fixes most coordination issues.

ice
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Mo references right now, sorry :( I can start a thread in another forum with guys that can explain it better then me but I know a large cogeneration edition requires relaying changes.
 
mbrooke said:
... Conversion will start from the top down by the looks of it. It will first take place as major Ultra high voltage links between generation and load pockets (as we see today), then moving to regional 500 and 345kv bulk transmission systems, down to local 138 and 115kv systems. It will proably stay like that for a bit until local 5-35kv class distribution lines go DC with the final process being utilization which imo will long have become at least partial DC in some places. The push for DC in utilization will only come from solar panels where maximum efficiency is obtained by bypassing inverters. Imagine feeding a 120 volt DC solar system into an ultra capacitor or super battery then being able to deliver that right to a receptacle, lighting circuit or directly out to the grid via simple protective device (separates system on loss of POCO) rather then energy wasting inverters.

In short, the power grid of tomorrow will allow all customers in all locations to add or deduct as much power as they like from the grid with minimal losses and exceptional reliability.
Click to expand...

Sounds great. What kind of time frame do you have in mind? I'm thinking a 100+years?

How about this:
15 years: Room temp superconductors in transmission use
25 years: Fusion plants on line
50 years: Cold fusion plants on line
100 years: Distribution is by beamed power

Yep, we will have to scrap all the distribution lines. Think of all the massive copper we can recycle

ice
 
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