Is more rotating mass sufficient to avoid grid collapse ?The
UCTE/Entsoe Official report discussing about a grid split in Europe on
4th November 2006 that occured after local overload followed by desynchronisation, provides some interesting figures an hinsights.
To have a sketch of what happened that night, you may read the related
Wiki page (English translation of the French wiki page, which is more detailed than the native english version) [refresh the Wiki page if english translation refuses to show up].
Let's focus on the 'Western Zone' also called
'Area 1', colored in orange (refers to the map of Europe in the Wiki page).
After the grid split occured, 'Area 1' underwent a
production-consumption imbalance of 8.9 GW for 182.6 GW production.
Wind power is 3.5 % of the production, solar production is logically not mentionned because incident occured at 10 PM in November.
So likely more than 90% of the production is provided by heavy turbines (steam for nuclear, gas and coal, water in case of hydraulic plant) coupled to massive generators.
When the grid split occured, the supply-demand missing power (8.9 GW) represents 4.8 % of the production in 'Area 1'.
At first sight, I would say that a less than 5% production shortage is not a big deal and should be quite manageable.
Now let's have a look to the
grid frequency in 'Area 1'.
In fact, the situation is almost desperate and grid is close to collapse : the frequency loss rate is 120-150 mHz/s so
after 8 seconds, 1 Hz was lost !
Remember that UCTE/Entsoe recommends to keep the strongest power plants connected
down to 47.5 Hz.
This means that without forceful and immediate intervention, total blackout is just 12 seconds ahead the 49 Hz mark (= 20 seconds after the grid split incident).
Situation is actually aggravated by this harsh frequency drop : at 49 Hz, some production plants have already tripped which leads to an additional
production loss of 10.9 GW.
Massive
load sheeding of about 16.7 GW, depriving around 15 million(*) customers of power could stop the frequency drop (min value was 49 Hz) and this was completed by connecting to grid almost all tertiary reserve available :
A total of about 16 800 MW was started in the Western area while the tertiary reserve declared in this area was about 18 500 MW. That means that in the Western area, almost all available reserves were started.15 minutes after the grid split, frequency was back to 50 Hz in 'Area 1' and syncronization + reconnection to other areas of Europe was performed
in about 40 minutes.
Luckily, western european grid total collapse and blackout was avoided.
Compare the November 4th, 2006 incident to what happened in Spain this weekRemark: this is my own attempt to provide some insights on how Spain dealt with the grid collapse.
You may of course have a different point of view.
Furthermore, no official reason for the outage has yet been released.
Q1) Could Spain avoid partial blackout at 12h32 CET ?
No, Spain (and probably no other country in the world) has sufficient tertiary reserve to compensate a 60 % production loss. Load sheeding is the sole solution to avoid immediate collapse and total blackout.
Q2) Is 'rotating mass' the ultimate solution for all kind of grid issues ?
No. By looking at the figures above, more rotating mass/inertia just gives more time to activate countermeasures (load shedding, put reserve production on the grid). But we are still speaking about a timeframe of a couple of seconds. To maintain frequency at its' nominal value (50 Hz for Europe) production must equal consumption every single moment.
Q3) How can network instability be limited in an energy mix that tends to increasingly favor renewable energies ?
As johansen underscores (see last sentence of
Reply #194), I would say that the grid monitoring system must be able to control (**) and monitor in real time a large part of the decentralized renewable power generation. The basic operating rules implemented in most vanilla solar inverter(***), once duplicated millions of times, likely weaken the grid stability.
It is also likely that raising the interconnexion capacity between regions/countries (= densify the network) improves the grid stability, but this needs heavy investements and all of those are not economically profitable or even possible.
(*) this is the figure for whole Europe, not not only 'Area 1'
(**) control orders like 'force connection' (if the sun shines of course), 'force disconnection' and the ability to modulate the injected power or a solar equivalent of the '
droop speed control' would certainly help the grid supervision system to better master the grid frequency. Early signalling of clouds (or other situations that
suddenly hide the sun 
) would also have beneficial consequences.
(***) the (too) basic and autonomous operating rules are : connection-disconnexion if within-outside 50 Hz ± 0.5 Hz and stupidly always fuel the grid with the maximum amount of solar power available.
Home
Help
Search
Login
Register
