New Zealand Power (from Don't Vote Labour)

[davereid]

Thanks for answering my question.

Just to expand on it abit as a hypothetical situation...Imagine we build a 360Mw nuke and all the other stations are scaled back to bring it back to 50Hz....then at 5am one morning when the nuke is still putting out 360Mw and nothing else is operating demand is only at 200Mw. The nuke cant be scaled back so continues to put out 360Mw which ups the frequency to (say) 70Hz at which point something explodes(power plant im thinking not, substation? individual houses?). Am I on the right track?

Not really. Nukes are not special. They are just good old-fashioned steam plants which rely on a lump of decaying ore for heat. So if there is insufficient demand for the electricity, you have waste heat. The electricity network doesn't care, its just that the reactor does. You just have to find somewhere to get rid of 360Mw of heat generation, less 200 Mw of electricity. You could dump the excess power in the waikato river. Or in the sea. Nuclear power is just a heat engine... How hot would you like to be ?

[Jantar]

Not quite. The turbines have under/over frequency protection which would trip the generator and scram the reactor.

[davereid]

Not quite. The turbines have under/over frequency protection which would trip the generator and scram the reactor.

Of course. The entire network has that ! Not just nuclear reactors !

Its actually a network problem, not a reactor problem.

We like to control TWO things... voltage AND frequency.

You can't go scramming a nuke, just because NZ steel blows a fuse.

And you can;t leave it running either, unless you want pre-fryed trout.

[sAsLEX]

Of course. The entire network has that ! Not just nuclear reactors !

Its actually a network problem, not a reactor problem.

We like to control TWO things... voltage AND frequency.

You can't go scramming a nuke, just because NZ steel blows a fuse.

And you can;t leave it running either, unless you want pre-fryed trout.

Pretty sure Jantar and even K14 should have a pretty good grip on the situation huh Jantar?

[davereid]

Pretty sure Jantar and even K14 should have a pretty good grip on the situation huh Jantar?

Its an engineering issue, not an energy trading issue.

With due respect to K14 and Jantar who ABSOLUTELY know what they are talking about, the entire picture is a bit bigger...

Its like this..

In the dark old days when it was discovered that swinging a wire in a magnetic field produced electricity, two schools of thought developed. Mr. Westinghouse & Mr. Edison picked a fight.

School "A" said - Use DC electricity. Low losses, only have to worry about resistance, pick me.

School "B" said - use AC - fuck the losses due to AC (reactive losses), electricity will be cheap. We will cope with the reactive power loss, because AC lets us use transformers to adjust voltage. We will lose heaps, but fuck, we just use a transformer to fix it later.

School "B" won the day, but with a catch.

If you design a transformer, you have to know what frequency it will work at. As it relies on inductance and reluctance to control its current consumption. ie, if you stuff 0hz into a 50 hz transformer, it wont transform anything, its just a resistor, and will get hot and blow up.

So..

We now need to control frequency as well as volage. Cos if there is to much demand, and frequency gets low, the transformers and network components get very unhappy. Same the other way. Transformers don't like going over frequency, nor do transmisson lines, and the rest of the network.

[Ixion]

,,

You can't go scramming a nuke, just because NZ steel blows a fuse.

And you can;t leave it running either, unless you want pre-fryed trout.

Why not ? You do realise the negative effects that this sort of irresponsible attitude has on popcorn sales, don't you.

[sAsLEX]

Its an engineering issue, not an energy trading issue.

With due respect to K14 and Jantar who ABSOLUTELY know what they are talking about, the entire picture is a bit bigger...

Well I hope your degree in physics is coping with this K14.........

[davereid]

Its actually why the Cook Strait cable is DC. Losses on 50hz AC systems are quite high. So when the Cook Strait cable was designed, it was decided to convert the power to DC at source, and then build a special power line all the way to Fighting Bay, just for the cable. Its "shipped" across Cook Straight as DC, then re-converted back to AC at Haywards. Maybe "School A" won a good percentage of NZs power network !

[sAsLEX]

Its actually why the Cook Strait cable is DC. Losses on 50hz AC systems are quite high. So when the Cook Strait cable was designed, it was decided to convert the power to DC at source, and then build a special power line all the way to Fighting Bay, just for the cable. Its "shipped" across Cook Straight as DC, then re-converted back to AC at Haywards. Maybe "School A" won a good percentage of NZs power network !

But how big is the DC switching gear?

Imagine that in every house? And which voltage would you pick for households? I mean AC can be easily converted around....

[davereid]

But how big is the DC switching gear?

Imagine that in every house? And which voltage would you pick for households? I mean AC can be easily converted around....

When the DC link was put in, conversion of DC to AC was tricky stuff. Red Hot Mercury Arc valves that scared the be-jusus out of young engineers like me ! And plenty of ka-pow f-ups to remind you the wires were made of metal and you were made of a much softer material !

Can't remember the capacity. 500,000 volts and 250Mw maybe.. (The clouds of time...)

But now, with solid state electronics, cheap inverters etc... what would we pick ?

Well, I guess, high voltage DC distribution. A 500,000 volt AC could deal with about 700,000 DC volts with a bit of luck. No reactive losses.

In your house ? Shit low voltage ie 50v would virtually eliminate electrocution deaths, although still plenty of respect for the wires. But that big heater in the lounge would need lots of Amps, and a big extension cord !

[sAsLEX]

In your house ? Shit low voltage ie 50v would virtually eliminate electrocution deaths, although still plenty of respect for the wires. But that big heater in the lounge would need lots of Amps, and a big extension cord !

Why volts dont kill!


I have had plenty of ten thousand volts hits before!

[Jantar]

Can't remember the capacity. 500,000 volts and 250Mw maybe.. (The clouds of time...)

Very close. The original HVDC was 250kv per pole with neutral earth return giving 500 kv between poles. and 300 MW per pole giving a total of 600 MW.

Maybe you have got a slightly incorrect view of what K14 and I do. Yes, we are Traders, but Dispatch/Traders, not financial traders. That means we come from a science/engineering background rather than an economics background. when it comes to turbine/generator and protection performance I believe we do have a good idea of what is involved.

[k14]

When the DC link was put in, conversion of DC to AC was tricky stuff. Red Hot Mercury Arc valves that scared the be-jusus out of young engineers like me ! And plenty of ka-pow f-ups to remind you the wires were made of metal and you were made of a much softer material !

Can't remember the capacity. 500,000 volts and 250Mw maybe.. (The clouds of time...)

But now, with solid state electronics, cheap inverters etc... what would we pick ?

Well, I guess, high voltage DC distribution. A 500,000 volt AC could deal with about 700,000 DC volts with a bit of luck. No reactive losses.

In your house ? Shit low voltage ie 50v would virtually eliminate electrocution deaths, although still plenty of respect for the wires. But that big heater in the lounge would need lots of Amps, and a big extension cord !

Yeah good old Pole 1 was taken permanently out of service in sept last year. Too many arc backs (I don't really know they work, just what i've been told) and since its so old they are running out of spares.

Now the HVDC is limited to just 700MW north and 500MW (iirc) south. Although those numbers are just that, it will never see over 500MW north and probably not more than 250ish south. So the days of the mercury arc valves are gone.

There are plenty of installations of HVDC lines thoroughout the world. The line to Tasmania was commissioned in 2001 or so and I was reading a quite interesting article in a magazine a few months ago about a new one connecting a few countries up in western africa. The main reason that you can't use HVAC underwater is the capacative effect, the losses are big enough when you have dry air surrounding the conductor but water just increase that by an order of magnitude or so.