Connect 120 volt circuits to get 240 volts

Networks are usually run with the N-1 rule, so assuming the UK average consumption is 25 GW, 4 % of it would be one nuclear power plant according to the spinning reserve principle

Then you start to drop loads.

Those are long term issue, not short term issues.

The UK network is quite small, but sufficiently large to avoid crashing it with a single failure.

Really ? ?

One criterion for selecting a hydropower plant for starting a black net is that there are _always_ water available to boot the net.

But it /isn't/ 25GW - unfortunately it is /much/ tighter than that.

The current demand is 34.39GW (Frequency 49.937Hz), At 5:30 tonight it was 40GW. On the 14th it looks like[1] it hit 45GW Plus we have abnormally warm weather at the moment.

[1] can't be bothered to download the database

Indeed.

"Notices of insufficiency" were issued a few months ago, i.e. telling businesses to be prepared to be cut off.

Er, if all the holes line up, it is an issue until another plant comes onstream. The current outages mentioned above will hopefully cease by end of March and end of April.

Three and four *months* isn't "short term" if there is insufficient generating capacity. I lived through that in the early 70s, and it wasn't fun.

Then it was politically motivated strikes. Now it is "free market economics", without effective sanctions. Both are equally bad. Bloody maoist libertarian claptrap; they ought to be taken out and shot.

t 240 volts at a home or business that doesn't have 240 volt outlets is to pick off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

ot

from the circuit. This also causes K3 to drop out no matter what since the re is no closed circuit for the current.

The load will be disconnected by K3. K3 drops out because K2 is now in the path of a 120 volt supply. K2 drops out because K3 is now in the path wit h a higher resistance than K2 has.

Not sure what you are describing here. JP2 neutral is only connected to K2 coil. Any path to this neutral will go through multiple coils and so drop out. Drop out voltages are part of a relay spec. It doesn't need to be r andom.

Again, not sure what you are trying to say about "proving" it won't not fai l? Are you talking about a load that returns power into the circuit? Like batteries?

Rick C.

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You didn't account for the impedance of the load itself.

Due to the nature of connecting 2 circuits together, it now has safety implications (a bit like a generator transfer switch) so you need to prove it's as failsafe as possible.

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That is a "forward" design, which assumes that, read left to right, it works. There doesn't seem to be much consideration for the many ways that it might not work.

I see that a lot, lack of consideration of failure modes and unintended states.

But I don't see why all that stuff is needed at all.

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anning-strategies/

Not much of a report.

"Analysts now forecast that EV energy use could rise from a few terawatt-ho urs (TWh) a year in 2017 to at least 118 TWh and as high as 733 TWh by 2030 ."

A 6 to 1 range doesn't pin much down. How much of the potential 733 TWh ca n be accommodated by the current generation capability if the increase were scheduled optimally? Not everyone has to charge during the day and those who do mostly charge in the middle. Cars are driven rather than charged du ring peak electrical usage hours. Most charging will happen at night and c an be scheduled.

ctric-utility-grids/

Again, poor reporting...

"An example is Colorado, where the number of electric vehicles has jumped b y 150% since 2011"

Duh! Where haven't EV usage jumped significantly from 2011 when most EVs w ere not much more than golf carts.

"In other words, introducing an electric vehicle to a neighborhood is rough ly the same as adding another house."

Total BS. Adding more homes means the power demand at any given time will multiply. Adding a new type of load to homes means the power demand vs. ti me will change. Not at all the same thing, especially when EV charging can be scheduled.

mode,

Which is Bill's thing. I don't think it will catch on because it wears the batteries... and that there is no real need for it. Any batteries the pow er company needs should be controlled by the power company.

Rick C.

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Yes, really. There is ~zero non-pumped hydro power in the UK, so it has to be pumped storage.

The other main reason is peak transient demand; they come fully onstream in, IIRC, 30s.

Nothing surprising there.

Ought to be.

But we are currently too close to the cliff, due to dimwitted politicians thinking free market economics will prevent that kind of things.

The free market demonstrably operates to maximise shareholder value by minimising investment and overcapacity.

Bloody maoist libertarian claptrap.

rge number of EVs.

t only on low power.

Who says EVs don't need block heaters? That battery needs heat to work eff ectively. That's one issue that can't be scheduled away, the morning pre-h eat of the battery. An hour at 6 kW or so at about the same time the heat pump thermostats are all rising a couple of degrees.

??? Where did you get this idea?

Rick C.

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That's a spec and part of the relay data sheet. Pick one that works according to the needs of the circuit.

Rick C.

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the path of a 120 volt supply. K2 drops out because K3 is now in the path with a higher resistance than K2 has.

fail? Are you talking about a load that returns power into the circuit? Like batteries?

So you are saying that by not disconnecting both legs when one circuit brea ker goes down there is a path through the load that can keep all relays in an active state? Except that K3 will drop out. Even if there is a sneak p ath, the load does not feed K3 240 volts. The load robs current from K3. The K2 coil in series with K3 combined with the half voltage would be suffi cient for a properly specified relay to drop out disconnecting the load and removing the sneak path you are describing.

Even so, if this were to happen, the harm is in feeding a low voltage to th e load. This is not a personal safety hazard. Since it won't happen anywa y, not to worry.

Rick C.

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So this is the storage battery for starting the UK power grid? Interesting.

Rick C.

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It doesn't matter if that 4 % is calculated from 25 or 50 GW as long as it is greater than the output from the largest power plant. Since the UK doesn't have any significant hydroelectric plants, the largest plants are nuclear about 1 GW (1000 MW). Thus this amount of spinning reserve satisfies the N-1 criterion.

Depending of power company and customer. Some real big customer may agree to cut their load a few hours a year (and lay off their workers) in order to get electricity cheaper most of the time during the year.

Power companies will cry loudly if they have to run expensive gas turbines for months instead of a few hours each year :-).

On 30/12/2018 21:28,

Yes.

Maybe.

As I said before: several problems:

1) It may not drop out in a specified and reliable time;

2) It will not (for a standard relay) provide suitable isolation for safety purposes (3mm contact gap in the EU, I would be surprised if the US did not have a similar line of specifications)

3) Will it drop out at all for every possible impedance of load (including all combinations of capacitative, inductive and resistive loads)?

The problem is if all relays remain powered for even a short length of time by parasitic currents, you are now backfeeding one house circuit into another that was presumed isolated due to its breaker tripping.

This could pose a hazard for anyone who comes into contact with that circuit. It would breach British regulations on those grounds. Regs or no regs, it's a bad failure case.

Which almost certainly does not need 240V to hold it in.

Here's a 10A 240V Omron relay:

"Must Operate" coil voltage is 80% of 240V = 192V

"Must Release" (min) is 30% of 240V = 72V.

That's awfully close to 60V if the remaining 120V circuit is split 2 ways and what's the tolerance on your supply? +/-10% on line voltage?

Plus this was the first relay I found - there may be others with lower Must Release voltages.

I'm going to stop now - it's a horrible design, and unless it's stamped "fit for purpose and independently tested" I wouldn't touch it.

Energising a dead circuit from another source is most certainly a safety hazard.

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The battery doesn't generate any huge amount of heat, so it can be isolated and warm it with a quite low power to keep it in optimal charging condition.

There is a charging station about 1 km from where I live and I have frequently used the bus line in the afternoon returning from the round trip towards the charging station. The bus accelerates quite strongly at the end o the leg, so a lot of power must still be available. Admittedly the total route is less than 10 km long, but this the second or third winter.

Plucking figures out of thin air and basing arguments on them does matter.

Of course; shrug.

Doesn't change the fundamentals one whit.

I don't care about that.

I do care if there are insufficient gas turbines or gas for them to do that.

Remember the lesson of the Ford Pinto. Ford decided it was better for their bottom line to allow drivers to fry to death than it was for them to correct their gross design defect.

Electricity companies can (and do) go bust and walk away from their obligations, leaving the consumer to foot the bill.

Yes, the structure of the UK energy industry sucks. It was designed on the assumption that "market forces" are the best way of solving problems. That's Maoist libertarian nonsense, of course. It may solve /some/ problems, but it exacerbates others since the risk/reward tradeoff is skewed.

no-one in the UK uses block heaters, so no such energy is available.

12k miles/yr is typical total mileage. Taxis more like 50k a year.

I doubt it. Even if possible, such a battery would be monstrously expensive as well as heavy.

NT