I hear this kind of misconception fairly often and so it is worth noting that you don't need 1400 MW of battery to protect from this event.
The initial 735 MW drop happened, as I read TFA, when a major generating source took itself offline as a result of the frequency disturbance. The later generator drops are cascades of the frequency disturbance earlier in time.
If a suitable battery had been present and reacting in milliseconds it could have stabilized the frequency enough, for just the very short period required, to avoid the whole generator trip in the first place. Thus you can use much smaller amounts of fast-response frequency support to avoid much bigger drops. This is how batteries can pay for themselves so quickly when placed in the right topologies w.r.t to the grid demand and generation resources.
So far the largest battery is 40 MW? So not really going to help more than 40 MW can, even if it comes online instantly, when 200 MW trips off.
It is basically a question of providing just enough frequency support, for long enough, for the remainder of the grid to respond to the frequency drop. In other words, let the frequency sag a bit so generators respond but not so much that they disconnect.
I think there's also some control system error implied in the wind farm's drop as I read the article. That perhaps shouldn't have happened at all and was an un-analyzed state that will be corrected.
>I hear this kind of misconception fairly often and so it is worth noting that you don't need 1400 MW of battery to protect from this event.
I would be interested in any papers or literature that have led you to this conclusion.
as soon as (generation - load) <> 0 the frequency is going to change. If you lose 200MW of generation and have 100MW of batteries that are configured with 0 or very small amount of droop they see some small change in frequency and crank out 100MW to try and stop it from falling further. Then they are maxed out, there is still 100MW of imbalance for conventional generation with governors to take up, which they will as the frequency falls as if the trip had only been 100MW in the first place. How is this not a 1:1 relationship, 100 MW of batteries displace 100MW of lost generation?
For this event in the UK in particular it appears the issue is that the large windfarm, and 500MW of small embedded or distributed generation are en masse improperly configured or by nature are not able to ride through any small transient wobble in frequency. TFA didn't show us what voltage these plants saw.
Although a 200MW steam turbine also tripped due to the same lightning/transmission line trip event, so clearly it was subjected to something that exceeded instantaneous thresholds and had to trip immediately. And then that steam turbine tripping caused the gas turbines at the same plant to trip which indicates there are some design or operational issues at that plant.
Also is 20s reclose time for a transmission line standard? I've only configured distribution line reclosers but it was more on the order of 1s for the first reclose and maybe 7s for the second?
Also battery reacting instantaneously to correct or mitigate a grid issue might avoid some other generator to go offline or allow to go offline for a must shorter amount of time avoiding some of the cascading effects.
It seems to me that the value of grid batteries is not just the nameplate capacity compared to other generation technologies, it is a class on its own.
May be once batteries are incorporated in the grid at some scale software triggers commanding other generators capacity disconnect/reconnect will have to be updated "let the grid batteries do their job first and then act".