China: Boldly Going Where No Grid Has Gone Before

[dlgoff]

Ummm... I've operated mere megawatt turbine generators, and tripped them off line, under full load.
It wasn't pretty.
But that isn't the problem I'm seeing.
I'm looking at, um, a lot of inertia, 3 orders of magnitude greater, with nowhere for it to go.
And that scares the bejezits out of me.

It's spread over a really big grid that's somewhat like a bunch of rubber bands. The dumped power isn't dissipated instantaneously.

 

[OmCheeto]

It's spread over a really big grid that's somewhat like a bunch of rubber bands. The dumped power isn't dissipated instantaneously.

But that seems counter to what anorlunda posted in his OP; "In July, CSG neutralized this threat by shutting off Yunnan’s AC links to the rest of its grid, turning the province into its own distinct synchronous zone."

But, as I've said, this is way too much information for me to process in just a few days, so, I'm going to take a nap.

 

[dlgoff]

But that seems counter to what anorlunda posted in his OP; "In July, CSG neutralized this threat by shutting off Yunnan’s AC links to the rest of its grid, turning the province into its own distinct synchronous zone."

Pretty sure those (disconnections) didn't occur all at once.

 

[anorlunda]

Ummm... I've operated mere megawatt turbine generators, and tripped them off line, under full load.
It wasn't pretty.
But that isn't the problem I'm seeing.
I'm looking at, um, a lot of inertia, 3 orders of magnitude greater, with nowhere for it to go.
And that scares the bejezits out of me.

You are quite right to be scared. I'll explain, but first let's simplify. Take the grid out of the picture. Imagine the circuit breaker closest so the generator at a hydro plant tripping. That is the worst case scenario from the generator's point of view.

There can be a huge amount of kinetic energy in the water traveling through the pipes (penstocks) leading to the turbine. Instantly, we give a trip signal the gates that close off that pipe right in front of the turbine. We can't close them instantaneously, or the force of the water would wreck them and wash the gates and turbines and generators and the whole power plant down the river. While they are closing gradually, the excess energy goes into accelerating the turbine and generator. 200% even 250% peak speed can be expected, so that is one of the limiting design criteria for the turbine generator. Remember, the breaker is open so the electrical behavior is out of the picture.

But there is still an enormous amount of K.E. in the water. As you say, it has to go somewhere. The somewhere is an engineered solution built into many hydro plants called a surge tank. The water surges up into the tank, converting K.E. to P.E. I heard that in some cases the water overflows the tank and creates a geyser shooting up into the sky. I would love it if some PF member could find a video of such a geyser.

Next step of complexity, imagine that a different breaker very remote from the generator trips leaving the generator with no load, but also with 1000 km of transmission line open-circuit on the far end attached. We call it radial load rejection, and it is very very stressful on the plant both electrically and mechanically.

p.s. You are touching on my favorite subject. I used to teach a course to utilities in the USA and abroad called "Generation Dynamics and Control" To me, that is a very fun subject. It incorporates the dynamics of every type of generation, and the grid, and how to orchestrate and control it both locally and system-wide.

 

[jim hardy]

I'm looking at, um, a lot of inertia, 3 orders of magnitude greater, with nowhere for it to go.
And that scares the bejezits out of me.

well it's not as if all the generators had to suddenly stop rotating when the breakers open. They just have to reduce their input power to zero before it accelerates them to dangerous speed. They can idle at synchronous speed if prime mover is available or coast down...
Our overspeed trips were 111% , indeed i saw one of our turbines at 3900 PM a minute into a regional blackout.
Our turbine inlet valves close imperceptibly fast so the energy available to accelerate turbine is only whatever steam is already in the turbine. To prevent acceleration we keep the generator breakers closed for ten seconds after a turbine trip. Should an electrical fault trip the generator from a high power level, an extra set of valves halfway along the multistage turbine snap closed to bottle up its high pressure half, that trapped steam gets released gradually so as to not overspeed kindly Mr Turbine.

Steam that's already en route to the turbine from the reactor gets bypassed to the condenser , dumping copious heat there. That's how the thermal inertia of the reactor system gets dissipated. Reactor system cools something like thirty degrees between full power and zero power.

That's a steam plant response. I defer to folks who've been around hydro for that scenario.
Windmills can feather and brake. But individually they're exceedingly tiny amounts of power . Our feedwater pumps were five megawatts apiece, about same as biggest wind turbine extant.

old jim

 

[mheslep]

That negative pricing, may be their own fault...

Negative pricing is caused by the wind subsidy of $23. No subsidy, no negative price.

 

[Windadct]

Found this List of Siemens projects - seemed to relate. Sorry - kind of a large PDF.

However on the issues of Subsidies - it REALLY is not black and white, examples,

The entire US telecom system was built on subsidies as a part of national defense, the mid-city "Bell Buildings" were heavily fortified (as in nuclear strike level) and the battery capacity was larger than probably needed. This infrastructure in turn made the USA a leader in many productivity, and technology fields. Would have never developed the way it did without federal money.
In the US home ownership is subsidized through the Fed loaning the banks money - to encourage home ownership.
The Coal industry HAS been heavily subsidized in environmental clean up, medicare cost to workers, as well as federal subsidy on rail infrastructure. Also - don't forget that the whole utility industry was built during regulation when every power plant was essentially guaranteed to make money through price controls. The coal industry has been on the ropes basically since the market de-regulated, Solar may finally kill coal, but it was already pretty sick.
The whole tech industry has benefited through government spending for space and defense - including the commercial development of solar technology.

All of these encourage behavior that will not occur through pure free market models - yes it is easy to look at a single policy and call foul, but it is a tool to promote change.

2c

 

[houlahound]

this recent event was manipulated by some politicians something of evidence of the failure of renewables.

investigations showed no link between wind and the black-outs. apparently storms can't tell the source when they are knocking out transmission lines and infrastructure.

the prices coal utilities charged to top up power appears to me to be to be opportunism and exploitation.

https://en.wikipedia.org/wiki/2016_South_Australian_blackout

 

[mheslep]

The entire US telecom system was built on subsidies as a part of national defense,...

I don't know the funding history of the original copper and microwave land line system, but the defense department did not pay for the cellular a network in place today, which was funded by commercial debt and user fees. So too the fiber optic network replacement of the copper and microwave landlines, though the FCC offers some subsidies to accelerate more "broadband" access.

but it is a tool to promote change.

Perhaps, and perhaps it is a tool to promote cronyism.

 

[OmCheeto]

Found this List of Siemens projects - seemed to relate. Sorry - kind of a large PDF.

Ah! Hahahahahaha!

But, as I've said, this is way too much information for me to process in just a few days...

I'm glad I'm not the only one:

Sorry. I just thought it was funny.

Siemens crew making pdf:

Person #1; "Where is 'The Dalles'?'
Person #2; "Nobody even knows where Oregon is. Just pick a spot."
Person #1; "Ok"​

However on the issues of Subsidies - it REALLY is not black and white, examples,...

It really is, quite complicated.

 

[mfb]

Even the Siemens picture shows that the terminal is at a river...

 

[OmCheeto]

Even the Siemens picture shows that the terminal is at a river...

There is a river where they put 'The Dalles".
Perhaps it was one of my cousins, playing a joke.
The Siemens picture looks quite similar to an aerial view of the Rogue Brewery.

 

[Guy Madison]

Here is an interesting item I would like to share. It seems that China has drastically pushed the boundaries of power transmission grid operations. They boldly go where no man has gone before.

How and why?

• The combination of geography and demographics leads them to place large generation resources very far away from the loads where consumers live.
• Excessively long transmission lines make HVDC attractive as a competition for AC.
• Excessive number of HVDC lines brings new operational challenges and opportunities, which they seem to be managing just fine.

They are doing things that old timers like me never imagined. Specifically, they challenged the catechism that increased interconnectivity of the AC grid is more reliable; a principle we used for more than 100 years. Hats off to them.

I think they are just spreading the pollution around, the further it is from your major cities it is the more it becomes someone else's problem. China builds all kinds of crazy infrastructure projects to keep the populous employed, it's been a big part of the economy there for years. Unfortunately most public work projects suffer from really shady construction practices which tends to shorten their lifespan so they get to build them all over again.

 

[mheslep]

I think they are just spreading the pollution around...

Not so much. Check the IEEE reference supplied by the OP.

...It operates more than 20 HVDC lines that deliver hydro, coal, and wind power from the nation’s interior to its eastern megacities. In southern China, five HVDC lines carry about 26 gigawatts of hydropower from mountainous Yunnan province to the coastal factories of Guangdong, ...

Also, the pollution harm from coal is not linear. That is, the collective harm from particulates and smog is not as great as when it's concentrated, say, near a city. So it may be true that the same amount of particulates are 'spread' around, but the harm is not the same.

 

[Guy Madison]

Not so much. Check the IEEE reference supplied by the OP.
Also, the pollution harm from coal is not linear. That is, the collective harm from particulates and smog is not as great as when it's concentrated, say, near a city. So it may be true that the same amount of particulates are 'spread' around, but the harm is not the same.

Sure.. but when it's away from a major city.. pollution becomes someone else's problem. Major coal plants even in the US are located away from major cities for the same reason, and it's so much much easier to offload coal trains in sparsely populated areas. Think of all the coal plants that line the interstate 90 corridor from Montana to Chicago.

 

[mheslep]

Sure.. but when it's away from a major city.. pollution becomes someone else's problem. Major coal plants even in the US are located away from major cities for the same reason, and it's so much much easier to offload coal trains in sparsely populated areas. Think of all the coal plants that line the interstate 90 corridor from Montana to Chicago.

I think you missed my point about concentration. Locating a coal plant in rural area is someone else's problem, but it's *less* of a harmful problem even on the individual basis, given the next plant is, say, 250 miles away instead of 10 miles away, possibly nobody lives within a couple miles of the plant in a rural area (unlike urban coal plants), the rural stack is, say, 100M tall instead of 40M in an urban area, etc.

 

[Guy Madison]

I think you missed my point about concentration. Locating a coal plant in rural area is someone else's problem, but it's *less* of a harmful problem even on the individual basis, given the next plant is, say, 250 miles away instead of 10 miles away, possibly nobody lives within a couple miles of the plant in a rural area (unlike urban coal plants), the rural stack is, say, 100M tall instead of 40M in an urban area, etc.

Maybe you missed my point, but that's exactly what I am saying. You put a coal plant away from cities. I am not anti-coal or all that, my dad made a lot of money building specialized stainless steel components for coal fired plants in the midwest.

If we are looking for polluters the media should publish more on bovine emissions.