Its like having a BIG OIL PUMP and having 100 people using oil all at the same time.. You PRESSURE varies slightly if the pump is not putting out enough flow.

TODAY, they have a VERY GOOD idea of how much POWER will be needed at 10 am TOMORROW, etc.

Thanks for a descriptive reply btw.

Every unit in the country is computer controlled to follow the load.. The "operator" is basically MONITORING the operation, not in DIRECT control of the unit... There are circuit breakers on the transformers at the sub stations and across the country that can "TRIP OPEN" in less than a second if something "MAJOR" happens.

FREEDGUY wrote: ...what happens in a storm outage situation where 10's of thousands of users  are  "OFF " during "non curve" times ??

Consequence of storm outage (or any outage event) is unrelated to how the system responds to demand change.

The short answer is, that when there's ANY large-scale astable action (a storm takes out a generating facility, a transmission line or substation goes down, etc), there's a chain of events that occurs that impacts basically everything across the system.  IF the components WITHIN the system are working properly, AND there's enough generating faciilities that can be properly managed, the system will 1) isolate failed segments and 2) restabilize itself around the remaining generation, transmission, and load.

In order to understand how the system responds, one has to understand how the components (both generator, and load, and the grid) operate.  I'll do my best to make it simple, but it ain't:

An AC generator running, develops two power characteristics... one is VOLTAGE, the second, FREQUENCY.  There are two devices which are necessary to CONTROL those characteristics... Voltage is controlled by a REGULATOR (which varies field current, which modulates field voltage via closed-loop feedback), Frequency is controlled by a GOVERNOR, which modulates throttle (regardless of wether it's an internal combustion engine, a combined-cycle diesel/turbine, a fossil-steam turbine, or a nuclear-steam turbine, or a hydroelectric turbine) to maintain a proper output frequency.

When a generator has no load, the only energy that is used, is what is requred to keep the generator spinning at governed speed, keep the field excited to reach regulated voltage, and operate the prime mover's housekeeping (like... cooling, lubrication, etc).  That means, a minimum amount of input energy (fuel) is required just-to-run, and once that point is met, adding an electrical load will cause input energy consumption to increase, hopefully in direct proportion to output demand, but things are never perfectly efficient.

Imagine you have one large electric motor, and one large generator powering it.  Ignoring all the startup issues, once running, the two will remain basically engaged such that the electric motor, with no load, will present basically no load (aside from friction and cooling, right) to the generator.  Add a load to the motor, and the generator will 'feel' it.  When a load is engaged, the voltage sags, and the generator engine becomes loaded, and slows, so the governor starts adding throttle to maintain proper speed.  The REGULATOR brings up field current to maintain voltage.  As RPM comes up, voltage rises TOO (voltage is a function of magnetic field intensity AND rotor speed through the field, so voltage rises as frequency increases, or as engineers say, V/Hz relationship).  Rising voltage makes the REGULATOR back off on field current, which reduces the prime mover's torque load, causing frequency to rise higher, until governor cuts off input energy, which causes RPM to start falling, which causes voltage to fall which causes regulator to raise field current...

See this viscious circle?  This is the realm of GOVERNANCE... trying to maintain a stable system, amidst inherently unstable circumstances.  [this is why there's a difference between tractor governors, and combine governors, and generator governors]

Let's say that motor, is actually 10,000 electric motors, all on the same trio of wires, and instead of one generator, there's 10 much larger generators, all on the same trio of wires.  That's the equivalent of 1000 motors per generator, right?

Now we get to the part of how to understand how AC generators can 'share' a same 'line'...

When you have several loads, and several generators, the generators HAVE to be SYNCHRONIZED.  It's like having a row of five-six engines, all in a line, with a clutch on the back of the first engine, driving the front of the second, which drives a clutch to the third, then fourth...  They ALL have to be synchronized, and they do this using those three WIRES.

In a bunch of clutched engines, if you apply a load at ANY point, it will have an immediate load on the crankshafts of ALL engines, but if NO engines respond with more throttle, the crankshaft speed will fall.  If SOME respond, the speed may not fall as fast, and if all respond, it may come back up, and overshoot the 'governed speed'.

in an AC grid, you have a BUNCH of generating plants, all coupled together, and as loads come on, they ALL 'feel' the load, but like the long line of engines example, the only ones that respond, are the ones that ADD more throttle.

Let's say, in that long line of say, 10 engines, you got 1 huge, and 9 tiny ones.  They're all hooked together, pulling a load.  The huge one is the ONLY one with a governor, and it is running at some particular speed.  The load is about 85% of what that generator can pull, while the rest is being pulled by all the tiny ones.  You have all the tiny ones' throttles pinned wide open.  They will NOT overspeed, because doing so means they're trying to spin the crank against the load FASTER than the big huge generator wants to spin.  When that happens, the really big generator's throttle closes, which causes THAT engine to reduce it's throttle.  The added load starts bogging down the smaller generators (after all, they're tiny), and the big generator's governor brings it back up to speed.

In the utility grid, you have several hundred large powerplants, and several thousand smaller plants.  Any plant that connects to the grid, synchronizes itself to the grid's waveform, and once engaged, attempts to increase voltage, and frequency of the grid.  in doing so, larger generating plants start reducing throttle, which causes more load to come to the 'new' plant.  Eventually, the new plant finds itself running at full-wide-open.

Engineers refer to this as 'infinite load' circumstance... effectively, the input power of a prime mover is at it's limit... like, you're climbing a mountain in a diesel truck... you eventually find a gear that will maintain a constant climb, while your foot throttle is totally planted to the floor.  The load (the grade) now determines how fast you'll go, because you simply have no more crankshaft power available.

Small generating plants that want to fire up and connect to the grid, and 'sell' their power, must synchronize, then connect in, and once in, add throttle, to try to 'push' the line frequency, and line voltage higher.  They'll advance the throttle either to some proportion of capacity to which they want to sell to the grid (basically, taking it from someone else's load).

The 'gotcha' is that this system works well if, and only if, there is:

1) plenty of plants that can run econcomically at PARTIAL loading

2) power sources on the line which are stable... not susceptible to being started or shut down without plenty of forewarning.

3) plenty of plants which can start rapidly, and 'pick up' lots of load when a station or line segment has been knocked out.

This is where most people are mislead:

When you have unstable power SOURCES, those power sources' lack of stability, cause a cascading domino-effect that destabilizes the grid. 

A wind turbine, for instance, is an 'unstable' source... it depends on wind, which might blow constantly for days, or even weeks, until a storm front finally arrives, and as winds go from a reasonable speed, up to an extremely dangerous speed, the wind turbine must 'shed' itself and shut down... feather it's blades, turn sideways to the wind, so that it doesn't self-destruct.  When this happens, it usually isn't just one turbine, it's literally HUNDREDS... and it all will happen over the course of say... five to ten seconds.

When that happens, power flowing in one direction on grid interconnections suddenly reverses direction, desabilizing the grid.  Small generating plants must respond rapidly in order to pick up the dropped load.

(this is where I explain the 'gotcha'...)

Every power plant has a 'minimum' input, just to EXIST.  A fossil steam plant (i.e., Coal) needs property, and a security guard, a bunch of insurance, property taxes, groundskeeping and environmental compliance, just to BE THERE.  A Nuclear plant requires even MORE, because it's a nuclear site...  It takes so much more, that the ONLY way to operate a nuclear plant, is to have it running at 100% load ALL THE TIME.  NOBODY will run one at partial, because the cost to run it at partial load, vs. full, is basically the same.  Nobody will EVER operate a nuclear-steam generating plant at partial, they also would not just 'shut it down' when there' was plenty of 'other' power competetors out there... it would, at that point, be a clear and total loss in terms of economic performance.

A fossil-steam plant, however, will consume less fuel at a partial, than full setting... and when shut down completely, will require very little (security, taxes, and insurance, and a little maintenance to maintain readiness), and when demand requires, they can be fired up in anticipation, or respond FAIRLY quickly to help 'pick up' a dropped load.

Unfortunately, they won't be immediate... so we will have to keep SOME of them ready, and running at a low loadpoint, so that they're ready for high demand circumstances.  "SOME" meaning... enough to pick up a considerable load... Like... about 200% of whatever the 'volatile' source is capable of (a 1 megawatt loss will need at least 2 megawatts of backup ready to 'pick up' for the sudden loss [*because a high-magnitude loss results in unstability that requires considerably more input capacity, just to stabilize*])...

The alternative, is to try to replace all the fossil-steam with solar and wind turbines... solar that generates full capacity, even in overcast skies and the dark of night... and wind turbines that generate full power, even when there's no wind, partial wind, or extremely excess wind...But there's no such thing as solar that generates in the dark, or wind that generates during doldrums, or stays operational and safe in a 120mph+ storm, and doesn't fall flat-on-it's face after the storm passes.

So with all this in mind, the circumstance that we will see in the future, is that when a storm or disaster causes some load destabilization event to occur, grid segments will go down, substations in the segments that TRY to recover will fry, 'reliable' generating systems will become 'islanded', and large quantities of people totally unrelated to an affected area, will be without power. 

Quality will plummet, cost will skyrocket, and we'll all be blissfully happy with the result... Or we'll be frozen or cooked to death... starving, without water... 'enjoying a primitive lifestyle', but that's what we call it 'progress'.

From Fulton MO we fed substations at Portage Des Sioux MO, Labadie MO, into REA subs as Thomas Hill, several in between stations as New Florence, Franks, Loose Creek and others to extend out like a spider web grid.  Callaway Generation Station made 345kv at 4000 amps to feed all those, as transformed into stepped down voltages of 34kv or 7200v amps went up as to available loading.  We could see the blips as Stations along lines all the way to our Sister plant at Wolf Creek Burlington KS would step ON or OFF the grid as to trips, maintenance outages, load demand adds or subtractions in all the readings where the generator was Auto Controlled as to load rates.  Steam rate would either increase or decrease to maintain generator speed and capacity factor.

Is almost Comical in that the Grid Load monitors could see when power thieves would set up a transformer CLOSE IN to transmission lines even as was not actually Hard Connected.  The Field Flux off the lines was so intense a Transformer of adequate size could actually function just being in Close(Like within 30 feet) proximity of those power lines, but the line amps would decrease ever so slightly indicative of a growing line fault where those transformers were attempted to be used.  Basically Tesla's theory put into hard function, electricity delivered thru open air without wires.  Yet the thieves were always caught.

Tbone95 wrote: I have a 320 Hp car. If I back out of the garage at 3 mph, requing, say, 4 hp, where does the unused 316 horsepower go?

If you're doin' it right, and enjoying the hot rod lifestyle, the other 316 are being disspiated as noise, heat, and shredded tires all over the garage floor! ;-)

(If you're my wife, the other 316 are being dissipated into the garage door which wasn't fully 'up' yet...

I realized I left out one ghastly important note, and in the interest of being thorough:

Line FREQUENCY is a regulated thing... in a given day, our AC line frequency is supposed to yield a SPECIFIC number of cycles IN ONE DAY, and they count them from a particular time.  It's been a LONG time since I worked in that industry, but I THINK it might've been midnight MOUNTAIN time (Boulder, Colorado being NIST's 'home').

When a small gen couples to the line, it is synchronized, and once connected, the governor and voltage regulator are essentially disabled... the throttle is opened up to full snot... and the plant engineer observes the prime mover's load, and the current limitations of the generator and his switchgear.

What the small plant is doing, is simple:  It is attempting to 'take over' an infinite (with respect to it's capacity) load... by trying to PUSH the frequency faster, and push the voltage higher... as it does, more current flows into the grid.  The grid's CURRENT flow starts to migrate towards the newly-connected generator, however, the load being proportionally infinite with respect to the generator's output capacity, the line frequency will not change appreciably, nor will the voltage rise considerably... and the little generator will work-it's-heart-out pushing in whatever it can, just like a hundred other small plants.

Until some executively-engineered uncontrollable supply is added, which destabilizes the grid and starts killing off the system's reliability... and more executive-engineering removes all the small and reliable 'throttleable' systems that keep the grid stable.

The answer he SHOULD be able to understand... is that there IS NO unused electricity. 

The load that all generators carry, goes either into a consumer load, or is lost in transmission... that loss being leakage to ground, heating of transmission componentry and wire (I2R losses) or heat and noise of reactive (L/C/R) losses.

In this respect, electricity is no more, and no less efficient than any other power source.  It is just very big, and very heavy.

When New Nuclear plants are Hot Tested they do not install Fuel Assemblies, they run the reactor coolant pumps and develop enough Raw Flow heat to deliver some 30-50 mw electric, with fuel that ramps to over 1200mw.

Well Stevie , you'd be 105% WRONG !! Kamps post made perfect sense!! Why couldn't YOU make a reply like his ?? Oh, wait, he's not in your TTPP club 

This IS the best BS reply I've seen on here this year  !!

I wasn't thinking so much as "GW's" but pure voltage coming down the line at any given time, I know the difference between amps and voltage btw 

T-Bone is damned by faint praise, by Mr Blobby, yet again!  If I were you, T-bone, I'd tweak his little pink tomato nose!

https://youtu.be/5ydgVZQctkk" rel="nofollow - https://youtu.be/5ydgVZQctkk

I am still trying to figure out where the 316HP goes, ya really got me. Suspect it's a trick question. Based on the current conversation, I will say "it goes out on the grid"?

I think more and more grid storage batteries are being installed. Horrendous infrastructure costs.

The grid is a fascinating thing. Consider we have thousands of roof top solar inverters

syncing up with the grid also. They just follow, they get no "vote" on what to do.

Even the green weenies are starting to think we need more nuclear power. Be more like France. Reliable baseline.

Kinda floating around in space till mama calls it home.

COMING MAMA... I'LL BRING THE BEER THIS TIME

DMiller wrote: A few older large base load stations have been converted to Grid Stabilizing Synchronous Capacitors,

They are the successor to Static VAR converters and Rotary VAR converters, and they operate on basically the same principle, with the two being combined into one unit.

They generally don't carry large systems  for very long... it's a function of how large the rotating mass is, and how heavily laden the system is.  Not a bad idea, but it's really just a 'hack' to try to fix what is actually a source reliability vs. load stability problem.

wellllll..

engine doesn't produce 350 HP at idle...

Perhaps one way to think about it is to use the  comparison of a water system to an electrical system in a low tech perspective.

In a water system the plumbing is always "pressurized", but water doesn't flow until a valve is open.  So, without a valve open, the water doesn't go anywhere, (not including any losses).  It's in the system waiting for a demand.

Similarly, in an electrical system the wires are always "energized", but the electricity doesn't flow until a demand is activated.  So, without a demand, the electricity doesn't go anywhere, (not including any losses).  It's in the system and waiting for a demand.