Electric grid, Generation and Infrastructure

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Lately I have been posting about the electric industry that does not really fit in the other threads. I will try this thread and see if there is any interest.


The WECC electric grid was messed up around 7:30 pm pst. On one node the real time power price was -$70 while a few miles away it was over $250 on another node in California. I have not seen negative prices very often but it seems very weird to pay $70 a megawatt to use power. Obviously it does not stay that way for very long.

The prices are different now but the impact this heatwave is having on the western US electric grid is obvious. The site shows among other things prices for three markets the real time the day ahead and a recently formed fifteen minute ahead market. Many of the nodes are not yet functioning in some or all of the markets. All of the nodes have joined the trading market but may not start trading for as long as two years away. This is one reason why prices in some regions still seem pretty independent of each other. There may be other reasons as well including insufficient capacity to move the power.
http://www.caiso.com/TodaysOutlook/Pages/prices.html

[nanning]

You made a separte thread for specifically the electric industry of the U.S.A.? (trying to stay out of the USA centric bubbles)
No global info?

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I made one for the electric industry full stop.
I frequently only post on the US not because I dislike the rest of the world or do not think it is important but because it interests me and there is more than enough content talking about the stuff local to me. I generally find the details on the local scale more interesting than the broad strokes. Someone who is interested could post similar things about Europe the same sorts of things are available there. They are probably available for many other countries as well I just have not looked. I invested a considerable amount of time learning how the US grid works. I spent hours and hours reading about it before I started posting anything. It took me while to find good sites with up to date information. If I wanted to do the same for other countries I would have to invest just as much time for each region to see how those places work and where to find that information. Up to this point I have been posting this stuff either in the renewable or coal thread mostly. At the moment I have gotten little response to this topic good bad or indifferent. That is fine I am mostly doing this for myself anyway. If someone responds to my stuff or posts similar stuff about other countries I may start learning about them and how they do things. So far the only response I have gotten other than yours was acknowledging my comments. Again that is fine I am interested in these things. In many of the threads some people only post about what is happening in a particular region. In most threads others post about the same topic in other regions. I doubt many others on this forum are all that interested in this topic as it is far from the main topic of Arctic sea ice.
I am in no way trying to exclude you or others from the conversation. I would prefer it if you join the conversation as I am not very interesting. If other people are only interested enough to read what I write and not interested enough to look for information and post themselves I do not know how to fix that.
I do care what is happening outside the US but the further away it is the less interest I have. I notice some posters primarily post about the UK. For a while there I believe you and Kassy? were posting about New Zealand? I assume that is your home country though I might be confusing who and where. While I have lived in different US states I have only ever visited another country once. I took a day trip to Canada. I don't know that much about other countries and if I do make any other international trips it will probably be either to Canada or Mexico. I would love to travel elsewhere but that is highly unlikely to happen. I write mostly about what I know (the US) and read about other places.
... so Yes Nanning I generally do not provide global info.

[kassy]

There are enough grid issues to keep us going for a while. In the Netherlands (So NL not NZ  ) the grid connections to places where a lot of solar will be build need to be updated...currently stuck in who pays land. And there are quirky EU things which i will add if they hit the news again.

[oren]

In Israel it's much the same, the southern desert can be filled to the brim with solar plants, there are many initiatives thanks to the low latitude and low cloudiness and very cheap land, but the interconnects to the northern population centers are the bottleneck. I participated once in some "hackathon" with the electricity authority, making some calculations of capacity and intermittence and so on, using their production scenario. According to them, new transmission is very difficult due to the permitting process (and environmental issues of damaging natural beauty etc.), this can take many years, current capacity already full during daytime, some new interconnects are already in the pipeline but it's very slow. One solution they considered was large batteries (probably 4 hours worth for each plant) that can store the energy during the day and transmit it at night when the interconnects have capacity available. Transmission can be staggered as the night is ~12 hours.
If not for the interconnect problem, Israel could and would boost its solar capacity much faster. Wind is much less relevant here, as the country is small with extreme population density, much area reserved as flight airspace, and location is smack in the middle of major bird migrations Europe-Africa.

[KiwiGriff]

In NZ there are grid issues as well
Its a long way from our hydro resource at the bottom of the south  island to the major center of Auckland .

 There is a large hydro plant in  Fiordland called Manapouri that presently supplies an Aluminum smelter in bluff.  Manapouri represents about 15% of the total electricity generated In NZ 
https://en.wikipedia.org/wiki/Manapouri_Power_Station
The company that owns the smelter has a long history of threatening to close the smelter unless they get large discounts for the electricity they use.
https://www.reuters.com/article/rio-tinto-newzealand-aluminium-smelter-idUSL4N2JO3RX
 If they do close the smelter it would free up a large amount of renewable capacity at a very cheap price. It  would cost about one billion NZ to upgrade the south island Grid and the Cook straight HVDC lines to get this energy to the north of the North Island. 
 The uncertainty over the future of Manapouri effects the willingness of Generators to build new renewable  capacity here.  This uncertainty means we are presently stuck burning imported indonesian coal for about 15% of our electricity supply.



 

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There are enough grid issues to keep us going for a while. In the Netherlands (So NL not NZ  ) the grid connections to places where a lot of solar will be build need to be updated...currently stuck in who pays land. And there are quirky EU things which i will add if they hit the news again.

Sorry sometimes I don't recall details as well as I should that is why I put question marks after those statements.

[oren]

It's even more confusing since Zealand is part of NL...

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Interesting. It seems they only way for the problem to get solved is to close the aluminum plant but that would cause other problems and they would have to build the transmission first.

[KiwiGriff]

It does not help when NZ is often missing from maps.

Grid connection be it across america or trans europe is an interesting question.
The Capacity factors for renewable energy make it cheaper to build a solar farm in spain or a wind turbine in the north sea. In both cases the cost of energy is  lower than the cost running an existing fossil fuel plant .
Grid connection across states or countries has become a major issue now renewables are the cheapest form of generation.   

[KiwiGriff]

Of course it is far more complex than my short post encompassed.

But jobsThe smelter drives a large part of the economy of the far south.
The smelters  output is both from 100% renewable energy and among the purest aluminum produced n the world. 
https://en.wikipedia.org/wiki/Tiwai_Point_Aluminium_Smelter
If the aluminum sold into the world markets  from Tiwai_Point is not produced from NZ's 100% renewable resources there  is a good chance it will be replaced from a less low carbon source.

The smalter is paying around 3.5 cents a kilowatt hour for electricity. Spread over the entire NZ grid that would reduce the cost of electricity by about 5 %.
Destroy the jobs of a few thousands in a remote region ? Or make the entire country that much more competitive  ?
Hard political choices.

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I haven't heard of anybody suggesting it anywhere but I wonder if upgrading from AC lines to UHVDC lines would help. The oscillating nature of AC power causes more stress on the insulator material than DC does. The insulator limits how high the voltage can be. Increasing the voltage lowers the amount of current needed to transmit a fixed amount of power. Temperature, humidity and current control how much heating occurs in the cable. The heating is energy lost in transmission and if it gets too high it causes powerlines to droop and potentially fail. Lidar power line monitors can provide real time feedback on how the powerlines are doing and allow operators to push powerlines beyond more conservative non-monitored limits.
If the voltage gets too high it will push the insulator off of the conductor.
The standard ac powerline used is rated at 500 KVA that is 500000 VA or 0.5 gw or 500 mw though for some reason 500 KVA is the preferred industry term. As I understand it the voltage used on 500 KVA line is 500,000 volts. That would indicate the current is less than 1 amp under normal conditions. That means the standard three conductors on AC powerlines provide 1.5 gw of power.  The voltage on some DC lines can reach 750000 volts. This may be the same cable or a special cable I am not sure. I know DC voltage rating are different than AC voltage ratings for the same cable. Equipment at each connection for DC is more expensive than AC which is why DC is more likely to be used to transmit longer distances while AC is used when the line will be tapped more along the way.  Two 750 KV DC lines carry the same amount of power as three 500 KVA AC lines. I do not know if it would make any financial sense at all to convert one to the other but I wonder given how hard it is to get the approvals for running new lines if it would be worth it to do this.

[sidd]

Re: KVA

In AC xmission, this refers to amps and volts, not watts, to calculate wattage you also need phase lag or lead between current and voltage. For example 500KVA at zero lag would be half a megawatt, derating as phase angle phi increases with a cos(phi) in there.

DC is a whole different can of worms ... undersea, for example, DC is preferable because the salt water surrounding gives more phase lag in AC. But as always, your mileage may vary.

sidd

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Re: KVA

In AC xmission, this refers to amps and volts, not watts, to calculate wattage you also need phase lag or lead between current and voltage. For example 500KVA at zero lag would be half a megawatt, derating as phase angle phi increases with a cos(phi) in there.

DC is a whole different can of worms ... undersea, for example, DC is preferable because the salt water surrounding gives more phase lag in AC. But as always, your mileage may vary.

sidd

Thanks for that I  have wondered why they used volt amps when that is watts.

[Jim Hunt]

Since you're referring to my specialist subject, I'll refer you to this recent heated debate about the current condition of the electricity distribution grid in the UK:

https://V2G.co.uk/2021/05/electric-vehicles-as-energy-smart-appliances/

Suppose a phase is about to overload – it will blow a substation fuse, sending many houses into darkness. This needs to be found in real-time.

How is this detected? IS this detectable? How? I can’t see a mechanism for that; certainly there is no real-time data for load control for our very weak LV systems… what data there is gets scattered to 101 retail suppliers. Who take no action thus BANG!

[NeilT]

I believe the North Sea interconnect between Norway and the UK just completed.

[kassy]

Since we have enough real issues with upgrading the grids i suggest to stick to those and not some tech fantasies in this thread.

[kassy]

I removed the off topic discussion.

[gerontocrat]

I removed the off topic discussion.

Boo hoo (crocodile tears).
My Pearls of Wisdom unceremoniously thrown into the dustbin of cyberspace.

Perhaps the ASIF needs a "dustbin thread" where moderators can hurl unwanted off-topic posts where ASIF vultures like myself can rummage through the rubbish.

Meanwhile...
Is it a multitude of smallish local projects like this one that if co-ordinated might take us a lot closer to zero emission electricity?

https://www.scotsman.com/news/environment/glasgow-energy-projects-worth-ps13m-will-power-cop26-climate-summit-and-help-blue-lights-go-green-3275437
Glasgow energy projects worth £13m will power COP26 climate summit and help blue lights go green

The United Nations climate summit, electric police cars and eco-friendly buses are all set to benefit from £13 million of green energy projects in Glasgow.

The energy projects will see £6m invested in the creation of new electrical circuits to provide extra capacity needed to supply the internationally important climate talks, which are expected to bring thousands of attendees from across the world to Glasgow in November.

When the conference is over, a substation will be built to house this new equipment and create additional electrical capacity for the city centre, helping to facilitate future green developments and connection of low-carbon technologies.

A further £6m will see a new substation built near First Bus’s Caledonia depot in the south side of the city. The facility will be critical in realising the public transport operator’s plan to introduce electric buses and set up the necessary charging infrastructure.

Upgrades worth £1m will also be carried out at 16 other substations in and around the city to support decarbonisation of the 3,500 marked and unmarked vehicles in Police Scotland’s fleet.

The project will contribute to the establishment of a ‘green corridor’ of electric vehicle charging points along key routes which will be primarily used by police to escort delegates and heads of state to the COP26 meeting.

[vox_mundi]

[Sigmetnow]

I removed the off topic discussion.

I think it’s a great topic.  I’ve started a thread for it over in The Rest.

https://forum.arctic-sea-ice.net/index.php/topic,3542.msg313178.html#msg313178

Feel free to stop over, folks, repost good stuff, and discuss further.

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It is sad to see how coal is doing this year.

[jai mitchell]

In the U.S. this is a primary issue.  However it is also a primary issue in every country so I think this is a great conversation to have.

In America, the western and south western states have excellent solar resources.  In New Mexico, recent solar farms are able to bid at prices far below OPERATING COSTS of existing fossil fuel power plants.

This means that it would be cheaper to import that electricity than it would be to maintain current fossil fuel infrastructure, which is not only providing more expensive energy but also is killing us.

However, if we import that cheap solar energy, then the utility companies (and hedge funds - finance capital - and their politicians that they keep in their pockets) will be bankrupted.  So they prevent the building of HIGH VOLTAGE DIRECT CURRENT (HVDC) transmission lines.  Usually by blocking them from crossing at the state level.

This same dynamic is happening all over the world with tons of very low cost renewable energy resoruces, typically found in lower-income regions of the globe, deserts and such, and the total technical feasibility of building out and importing that energy.

So as it stands now, without the ability to bring in (or export!) the energy, regions are required to buy long-term power contracts from peak power suppliers (at exorbitant cost!) to make sure that they have the power supplies they need during peak demand (heat wave) periods.

See the image below of California's power grid - as big as most other countries - the solar peak should look like a perfect bell that moves just above 12,500 MW of supply.  It is being curtailed with that broken curve being wasted energy, turned into heat, because they are opting to buy from fossil fuel imports at higher prices, for reliability.

The obvious solution is to take things over from a nationalization perspective.  To force open the markets by building out HVDC supply lines using the federally owned transportation corridors of federal rail and highway systems.

This would allow huge amounts of power to be provided across country at very very low prices, as well as allow for the time zone difference to allow solar to provide the evening power demand of the eastern regions, after the sun has gone down.

https://19fgew3zyb632ma8181lw82b-wpengine.netdna-ssl.com/wp-content/uploads/2020/09/NextGen-Highways-Sept-22nd.pdf

This is also analogous to every other country, both the challenges and the solutions (and benefits)!

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Jai I agree California and every where else need more grid infrastructure to make renewable energy work.
California though has a slightly different problem than other locations. If you look at their curtailment reports roughly 80% of renewable curtailment is because of local congestion. Most utilities do not allow local congestion to become much of an issue. California has a substantial NIMBY problem it is difficult to build anything there. Most US states want power produced in state to keep the jobs local but California is one of the few exceptions they fight any type of power plant. All of the surrounding states feed at least some power into California. Most of the imported power is hydropower from the Columbia river but it would be fossil fuel power if that was not available. I have included a real time price map of California electrical nodes. Dark green the power producer gets paid about $55/mwh. Light green the power producer gets paid about $45/mwh. The blue ones they lose a few cents for every mwh they produce. The black ones they pay about $150/mwh for the privilege of producing power.  The difference in prices is a congestion charge or how much the power producer pays to use power lines. All the other regions in the western US power prices are the same within a dollar or two for each hour all day. In California most days some large disparities between adjacent nodes occur during much of the daytime. Some of this may be because of wildfire risk and disconnecting some areas but much of this is due to local congestion.


I have included a graph of how much renewable energy is wasted every month. That is a lot of wasted energy.
The last graph is year to date curtailment by hour. All of the economic local is because some other generator(primarily natural gas) paid a congestion charge in excess of the value of power provided. The energy curtailed for economic system occurs when the region has too much power. This can happen when all the power needed is provided by renewable sources or when other generators refuse to shut down.
I have noticed that plant operators in pacwest (mostly Oregon and Utah) have learned to operate their plants in hot standby mode. To protect the steam turbine from thermal stress a cold start takes about 5 hours to 8 hours. That is why traditionally steam turbines only start when they know they can run for at least a couple of days.  Someone realized that it does not take that much fuel to keep the plant at temperature when not generating power. This is called hot standby mode. While some fuel is wasted it uses much less fuel than running all day. Most of the thermal plants in the US could be operated in this way to better accommodate solar and wind but they are not. This is primarily a training issue. Engineers need to determine what settings are appropriate for hot standby mode and teach operators as it has not been done before at most plants. If California operators learned to run their cogeneration natural gas plants in hot standby mode more of them could turn off during the day and save money in the process. Paying to produce power must really reduce profitability.

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California grid continues to fall short. The black spot is $-476.22 per megawatt hour is next to a maroon spot at $716.16 per megawatt hour. In general the orange spots are over $100 per megawatt hour. Republicans blame it on renewable energy Democrats blame it on climate change. Until those in charge acknowledge the real problem is NIMBYism no significant progress can be made. This is why I hate politics.


P.S. California is approximately 9 gw short of generators (of any type though I know they should be renewable) and massively short on the grid infrastructure to move what power is available around.

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Much of California just shot up to over $600 per mwh. Most likely a thermal plant tripped and went offline. And now some shot up to over $1000 per mwh

[sidd]

Re: dollars and units

thos prices are for MWH (MegaWatt Hour) , not MW

sidd

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Re: dollars and units

thos prices are for MWH (MegaWatt Hour) , not MW

sidd

oops did it again

[Iain]

And there is a heatwave on it's way, temps expected to exceed 100F.

This helps make the case for local production and storage - at the domestic level or local substation, so to reduce reliance on the grid or local network

I can see aircon competing with other new load additions - car charging, cooking.

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Ideally the power price should not vary much across the entire western US. Maybe vary by as much as $10 per mwh. Most of the regional grids seem to mostly accomplish this within their region. This map represents near peak demand on the yearly and daily cycle so I expect it to not quite be ideal. The cost of power certainly should not span several hundreds and sometimes a thousand or more dollars on anything like a regular basis. Most of these warm days near late afternoon congestion charges add at least a hundred dollars and often several hundred dollars to power costs. This grid desperately needs improvements.
While I certainly understand the impulse to want to have all generation local beyond some point the more local it is the more overbuilt the system has to be to be reliable. If everyone has there own solar and batteries for all of there own power needs that is extremely wasteful. On the other extreme building all generation assets in one location requires a massively overbuilt grid. The most cost efficient and least resource use is somewhere in-between.

[SteveMDFP]

Ideally the power price should not vary much across the entire western US. Maybe vary by as much as $10 per mwh. Most of the regional grids seem to mostly accomplish this within their region. This map represents near peak demand on the yearly and daily cycle so I expect it to not quite be ideal. The cost of power certainly should not span several hundreds and sometimes a thousand or more dollars on anything like a regular basis. Most of these warm days near late afternoon congestion charges add at least a hundred dollars and often several hundred dollars to power costs. This grid desperately needs improvements. ...

I do wonder if Musk's Boring Co could play a role here.  Nobody wants high-tension power lines overhead.  But perhaps underground tunnels wouldn't engender such resistance.  His tunnels are small-ish in diameter, but should be quite roomy for power lines. Maybe conductive walls to shield out any EM radiation.   Add some fiber-optic cables if needed, too. 

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Here are the daily generation numbers. The dips generally line up to weekends. the total uses the scale on the right everything else uses the scale on the left. I am not sure if there is any benefit to looking at the data this way. Please indicate if you think this presentation has value.

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Ideally the power price should not vary much across the entire western US. Maybe vary by as much as $10 per mwh. Most of the regional grids seem to mostly accomplish this within their region. This map represents near peak demand on the yearly and daily cycle so I expect it to not quite be ideal. The cost of power certainly should not span several hundreds and sometimes a thousand or more dollars on anything like a regular basis. Most of these warm days near late afternoon congestion charges add at least a hundred dollars and often several hundred dollars to power costs. This grid desperately needs improvements. ...

I do wonder if Musk's Boring Co could play a role here.  Nobody wants high-tension power lines overhead.  But perhaps underground tunnels wouldn't engender such resistance.  His tunnels are small-ish in diameter, but should be quite roomy for power lines. Maybe conductive walls to shield out any EM radiation.   Add some fiber-optic cables if needed, too. 

That is an interesting thought. I don't know anything about cost or any other requirements but that would solve the I don't want to have powerlines ruin my view issue.

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I just noticed that congestion price across the western US is at least $94 per mwh.

[Tor Bejnar]

The local electric utility last year replaced the underground cable in our neighborhood.  35 years ago they dug trenches.  This time they drilled 'horizontally' (we have some hills) from pit to pit with a 3" bore (7.5cm) or somelthing, about 50 meters per pit I'd guess.  Lots cheaper than boring a tunnel!

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I dont know if that would be deep enough. However tall those high voltage lines are they would need to be buried at least that deep I think.

[Sigmetnow]

'Extreme fire behavior': 2 firefighters killed as Western wildfires intensify during heat wave
July 10, 2021

[Two] firefighters were killed in a plane crash while conducting aerial reconnaissance over the Cedar Basin Fire near the Prescott National Forest, the Bureau of Land Management said in a statement.
…
Meanwhile, the Bootleg Fire in southern Oregon doubled in size Saturday to nearly 77,000 acres in the Fremont-Winema National Forest, interrupting three electrical lines that transmit power from Oregon to California, energy officials said. As a result, California lost thousands of megawatts of imported power and struggled to maintain operating reserves as temperatures soared into triple digits in parts of the state.

California Gov. Gavin Newsom signed an executive order Saturday to free up additional energy capacity for the power grid during the heat wave and growing fire threat. The order allows ships berthed at California ports to use auxiliary engines rather than shore power to relieve pressure on the electricity system.
…

https://www.nbcnews.com/news/us-news/serious-situation-western-heat-wave-wildfires-threaten-california-power-grid-n1273635

[SteveMDFP]

I dont know if that would be deep enough. However tall those high voltage lines are they would need to be buried at least that deep I think.

Well, the bores can be quite deep.  But I think the rock and soil around the tunnels will tend to attenuate EM radiation more effectively than air.  Perhaps especially if there's moisture in the ground.

I would think the limiting factor to power transmission would be keeping the 3 wires (with 3-phase transmission) at some significant distance from each other, and also some distance from the wall of the tunnel. 

[Bruce Steele]

Calif. grid seems to be of interest. Check out this site !  Shows real time renewable deliveries by the hour. Also show demand forecasts and tracks hour by hour how the day proceeds.

https://www.caiso.com/TodaysOutlook/Pages/index.html

[sidd]

Re: buried power lines

HVDC offers advantages here. 3 phase AC limitations, requires 3 lines and usually ground line, and cable reactances are an issue as is spacing between lines. DC needs 2 conductors, and line reactance is much less of an issue.

Depth does not need to be anywhere near tower heights, below frost line will suffice.

sidd

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Grounding is done locally where the power is used generally at the meter and the pole. Metal towers are grounded as well but a forth conductor is not used to move bulk power. DC would still have the advantage having only two conductors.
Grounding conductors are there to carry current back to the breakers under fault conditions. During normal operations they do nothing.


I have my doubts that burying (whatever the method) a half million volt dc line at two meters would be considered safe. I don't know what depths are required it might only need to be half the depth with DC but it will be significantly deeper than your neighborhood 18 KV lines.

[sidd]

We got a buried 33KV 3 phase line with ground running to a pad mounted tranformer delivering (also buried) 3phase 408V at an industrial site. Six feet deep, the electric company wanted four but we were doing the trenching ourselves, and we went down further. Total 33KV run is about a half mile to the transformer.

Usually we woulda put in poles, but getting a utility crane, auger, poles and such into the locations was a total bitch and we couldnt have turned the combine around in the field after the poles went in. So they totally went for it when we told them we would do the dig to their requirements or better. The utility techs tell me thats about as deep as they go in PA. They dont like buried cables for two reasons, finding faults is harder, and replacement is a lot harder. But they werent the kinda techs that do the half million volt xmission over a thousand miles either.

sidd

[sidd]

I should mention that dairy farmers really hate the electric delivered with ground return, it was too easy to wind up electrocuting your cows ... I knew a couple dairy farmers round harrisburg who got bit by that one. Didnt lose any head, luckily. These days, they put in ground current detectors and giant copper ground spikes in at  the facilities, but they still dont like it.

sidd

[sidd]

I should also mention, that ground return current is zero only when the current load on all three phases adds vectorwise to zero in direction and magnitude. This is not always the case and must be accounted for in design.

Delivering single phase with one wire no ground is automatically unbalanced,(still exists in the USA) and is a dangerous game, since all load current must return thru ground ... leading to the cow electrocution cases i spoke of.

You can try split phase rather than three (180 degree lag instead of 120); that wants a neutral conductor (which, to keep things comlicated, is different from ground but usually tied into ground at some point ...)

In my experience, i always prefer star 3 phase as opposed to delta for those reasons, i have an explicit return rather than one implied thru ground.

sidd

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When I look at the large electrical towers running from the local power plant I see three hot lines. The local power poles near my house are also three lines but I know that is two hots and a neutral (return line not ground). That is what I based my comments on. I have been shocked in older house without a dedicated ground as well so no need to involve defenseless cows.  If it needs a ground line than so be it I leave that up to the engineers. If the cows are getting shocked than there is a problem with the electrical that should be fixed.


As I understand it amperage is important to EMF as well as voltage. The amount of energy to power one location is far less than running enough power for a small city. I also understand that standards may very. The national electrical code or NEC (US) is usually adopted by most US jurisdictions but not always. I am familiar with 2012 NEC code but I do not know what has changed since then.


Extended exposure to high EMF fields has been linked to cancer. These fields dissipate very quickly with distance. I recall something like dividing by the cube of distance. Mostly with normal levels of power used around the house it is not a problem. I read somewhere that electric blankets can be a problem because they are so close to the body for 8 hours a day. A brief exposure is not a problem either statistically.

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I understand how an per mwh charge goes from positive to negative but I do not understand why a congestion charge would go from positive to negative. I am confused. Anyone know what I am missing?

[SteveMDFP]

Re: buried power lines

HVDC offers advantages here. 3 phase AC limitations, requires 3 lines and usually ground line, and cable reactances are an issue as is spacing between lines. DC needs 2 conductors, and line reactance is much less of an issue.

Depth does not need to be anywhere near tower heights, below frost line will suffice.

sidd

Thanks sidd!!  i was hoping you'd chime in on this.

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As with many things there may be a difference between legal requirements and a good idea. National electrical code requirements are deeper than 4 feet. If your local jurisdiction chooses to ignore that code that is just vested interests having an influence not that it is safe. At high field strength and extended exposure electromagnetic fields are dangerous. Thankfully those fields disapate quickly with distance. Dirt does provide better shielding than air but not as much as you would think. Most of the energy in AC power travels outside of the conductor. The better shielding dirt provides the more resistance to transmission it provides. Digging deep is expensive so it may not be required that does not mean they shouldn't.
DC power floes inside the conductor. For burial DC power is definately better the issue here is distances. When I look at the map of California the nodes are right on top of each other distances vary but most nodes are less than 50 km apart.


According to this source cost break even point is about 800 km for overhead lines and 50km for submarine lines. There are assumptions in those numbers that can change but they do not list a burial number. It may be shorter for burial but I really do not know.
https://electrical-engineering-portal.com/analysing-the-costs-of-high-voltage-direct-current-hvdc-transmission
400 miles breakeven ac vs dc
https://ddears.com/2018/06/12/ac-and-dc-transmission-lines/
"The cost of putting DC transmission underground will be about the same as putting AC transmission underground, with costs in urban areas higher than in rural areas." I am sure that is based on conventional digging.
[/size][/color]
[/size]Everything I can see suggest much of what is wrong with the California grid needs would be cheaper to fix with AC than DC though tunneling might be helpful where opposition to unsightly infrastructure occurs.[/color]


[/size]I am not really sure about this source but...[/color]
[/size]https://ddears.com/2018/06/12/ac-and-dc-transmission-lines/[/color]
[/size][/color]
[/size]"Roughly speaking, it costs three to ten times as much to build a new transmission line underground as overhead.
[/size][/color]Converting an existing single, three-phase AC overhead transmission line to an underground line costs:[/font][/size][/color]From $1.1 million to $6 million in a rural areaFrom $0.5 million to $12 million in urban areas"[/font]
[/color][/size][/color]
The source confirms that the same amount of power can be transported in 2 dc cables as 3 ac cables of the same size. They also imply that three cables are used for bulk AC power delivery not four. The ground is placed near places of consumption not near generation. The power pole where power enters the property is grounded as is the main panel as well as some sub panels.


Conversion of AC to DC and back again causes high losses but line losses are about 30% lower with DC compared to AC.


[/size]https://www.google.com/search?q=boring+tunnel+cost+per+mile&oq=boring+tunnel+cost+per+mile&aqs=chrome..69i57j0i390l3.11426j0j7&sourceid=chrome&ie=UTF-8boring tunnel 10 million per mile.

A Boring tunnel would put costs at the upper extreme per mile.

[Sigmetnow]

Tesla launches its own virtual power plant with Powerwalls to help California’s grid

Tesla is launching its own virtual power plant with the Powerwall in California in order to help the grid, which is expected to be under pressure this year.

A virtual power plant consists of distributed energy storage systems, like Tesla Powerwalls, used in concert to provide grid services and avoid the use of polluting and expensive peaker power plants.

Tesla launched such an initiative in Australia in partnership with the local government in an attempt to reduce electricity rates.
In the US, several companies, like Swell, have used Tesla Powerwall battery packs to build their own virtual power plants and offer grid services to electric utilities.

Now, Tesla is launching its own virtual power plant in California to help the state’s grid:
“The California grid operator forecasts a continued need for Californians to support the grid through 2021. Help create the largest distributed battery system in the world and avoid dependence on the least efficient fossil fuel power plants. Opt-in to the Tesla Virtual Power Plant (VPP), and Tesla will dispatch your Powerwall when the grid needs support while continuing to maintain your energy security.”

California’s grid is expected to have an exceptionally difficult few months, with record high temperature increasing energy demand on the grid and a significant drought affecting hydropower plants, like the Hoover Dam….

Tesla plans to enable homeowners in California who currently have Powerwalls to opt into the virtual power plant program and allow some capacity of their energy storage to provide power to the grid.

The company lists some of the benefits of joining the Tesla virtual power plant (beta):

• Stabilize California’s Grid: The extra capacity your Powerwall provides could help avoid or reduce blackouts in a severe emergency. This way, Powerwall can keep the lights on for both you and your community.

• Clean the Grid: Tesla will dispatch your Powerwall when the grid is in critical need of additional power. That is when the least efficient generators would typically come online.

• Unite as a Tesla Community: Team up with other Powerwall owners who are accelerating the world’s transition to sustainable energy and help form the largest distributed battery in the world — potentially over 50,000 Powerwalls. As part of the VPP, your Powerwall will have an outsized positive impact on the grid over traditional demand response programs.

• Keep Your Energy Security: Powerwall will discharge during VPP events but won’t discharge below your backup reserve. Adjust your backup reserve to control your contribution while maintaining backup energy for outages.

• Export Credits During Peak Periods: You don’t need to change your home energy usage behavior to participate. Additionally, if you’re part of a net energy metering (NEM) program, you may earn net metering credit for your energy sent to the grid during events.

Tesla plans to open up enrollment into the VPP through its mobile app starting on July 22. We will be on the lookout for all the details on eligibility.

https://electrek.co/2021/07/16/tesla-launches-virtual-power-plant-powerwalls-help-california-grid/

[sidd]

More detail on undergound xmission than most people want:

https://ccaps.umn.edu/documents/cpe-conferences/mipsycon-papers/2011/undergroudpowercableconsiderationsalternativestooverhead.pdf

As i suspected, EM field exposure is lower for buried AC cable even at modest 1m depth if  one is more than 10 ft sideways away from ground level projection of overhead or buried line, fig 5. DC  is a similar calculation, but not done in this paper.

Shielded cables have, of course, zero EM outside ...

sidd