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I've heard the layman's description of electrical grid response time before - it usually contains the word "instant" or "real-time". But I'm interested in the actual response times of the various types of power generation.

My limited ability to research has led me to articles on the three major "layers" of power generation: base load generation, load following generation, and peaking generation. I understand the high level difference between the three generation types, and roughly the kinds of plants that fulfill them. It seems that fuels like nuclear or coal serve the base load because they have slow response times. And on the other end of the spectrum, fuels like natural gas serve the peak load because the generation systems can be set up for fast response times.

That high level information has been easy to find, but I'm having trouble finding actual numbers. These are the only numbers I have so far:

But I feel like "start up time" is very different from response time, and I can't find any data on that. But maybe I'm working with bad assumptions - do these plants actually need to respond to instantaneous changes in load after they've started up?

If yes, which plants handle that kind of response, and how fast do they react?


Electrical engineering and power systems are quite far from my day job, so I'm not very good at constructing queries to answer my questions. Apologies if this has a trivial answer sitting somewhere else.

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  • \$\begingroup\$ This article does not exactly answer your question. But it is somewhat relevant and interesting. greenmatters.com/news/2017/12/22/Y0HJx/… \$\endgroup\$ – mkeith Nov 17 '18 at 18:39
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    \$\begingroup\$ This is impressive as well, 0 to 1320MW in 12 seconds : electricmountain.co.uk/Dinorwig-Power-Station \$\endgroup\$ – Solar Mike Nov 17 '18 at 18:44
  • \$\begingroup\$ A mere 2 cubic miles of pumped storage, the water pumped up 1,000 feet, will store enough energy to supply all of USA with 1,000 watts per citizen for 24 hours. Or is that 3 cubic miles? I forget. \$\endgroup\$ – analogsystemsrf Nov 18 '18 at 4:43
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The "fast" response you're thinking of is called frequency response. The grid consists mostly of generators and motors which "electrically" rotate in sync with the grid (the physical rotation being different by the slip). When the load on the grid exceeds the supply, they slow down and frequency decreases (slightly). When the power input to the generator is increased, or the power output of the load decreased, they will attempt to speed up the frequency will increase (slightly). The excitation current of the generator also affects this.

So the inertia of the grid provides the fastest response, where any sudden increase in load or decrease in generation is matched by a decrease in frequency. Then fast-responding plants will increase throttle/power input to the grid and frequency will stabilize. With thermal power plants opening the throttle like this does not change the thermal output of the plant, so if sustained would cause a decrease of pressure at the turbine inlet and loss of power.

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    \$\begingroup\$ "So the inertia of the grid..." Note that this is real true mechanical rotating inertia, not an analogy or metaphor. \$\endgroup\$ – TimWescott Nov 17 '18 at 18:29
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    \$\begingroup\$ @TimWescott Until very recently yes, but with the advent of demand response and grid battery storage there is also "virtual" inertia in the system. \$\endgroup\$ – τεκ Nov 17 '18 at 18:34
  • \$\begingroup\$ That's extremely helpful. So to put it in terms of your diagram, A to C is handled by grid inertia, C to B is handled by the fastest acting peak load plants like hydro batteries, and from D onwards is handled by the slower acting peak load plants like gas turbines? \$\endgroup\$ – kdbanman Nov 17 '18 at 19:20
  • \$\begingroup\$ @kdbanman Almost. C to B and D onwards are not necessarily different plants, but can be different methods of control at the same plant. For example a steam turbine might have throttle control for C-B (causing boiler pressure to begin to decrease), but increase boiler pressure for D onwards. \$\endgroup\$ – τεκ Nov 17 '18 at 20:21
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    \$\begingroup\$ @kdbanman Don't know unfortunately. It's from this pdf \$\endgroup\$ – τεκ Nov 18 '18 at 0:54

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