Came across this interesting analysis of the blackout. I don't recall having seen any discussion of the event in here so far ...
... Little Barford power station tripping at 16:52 when its declared maximum output ... dropped from 664MW to 0MW. ... Almost instantaneously, the Hornsea One wind farm (units 2 and 3) tripped, dropping its output from 756MW to 0MW, increasing the severity of the event.
So a loss of near 1½GW - not an insignificant loss of supply. From other news reports, it seems there was a lightning strike that caused Little Barford to trip - but it also triggered systems at Hornsea One which caused that to trip.
There then follows quite an interesting discussion of what happened next. The level of renewables (and interconnects) get a mention, specifically regarding their asynchronous nature. Big synchronous machines have a fair bit of mass spinning round and this helps support the grid over transients - but the level of that has been falling. It does say that the amount they had at the time "should" have been sufficient according to National Grid's previous statements.
A significant secondary effect is fingered as making the problem worse - significant amounts of embedded generation tripping as the frequency dropped quickly.
One other factor that may have added to the problem and explain the secondary drop in frequency is small embedded generators also tripping because of the sudden initial drop-in frequency. These changes have been an ongoing issue for several years with Ofgem continuing its work to make embedded generation more resilient to changing frequency events with a modification[1] being approved at the start of August. This will make embedded generation units below 5MW more resilient to Rate of Change of Frequency (RoCoF) events in the future.
I know we've had one or two discussions in here about how inverters detect loss of grid. It would appear that many of them interpreted the rapid drop in frequency as loss of grid and tripped out. It seems that this has been the subject of some work already and they are already widening the tolerances. That's fine for new kit, but I can't help thinking that few installations will get software upgrades - and given that FITs have beens scrapped for new solar PV, I think that future installs (with the relaxed tolerances) will take some time to become dominant.
The farcical situations with the trains gets a mention.
Questions also need to be asked of the non-energy sector as to why, for example, railways, took several hours to restore power ...
It seems a serious design issue if trains need an engineer to switch them back on. You'd think that power disconnections would be fairly common - eg pulling into sidings and dropping the collector pantograph/lifting the pickup shoes to disconnect from the supply while parked. I've been on a train where they were having problems, and the supervisor told us they were going to "switch it off and on again" so we didn't panic when the lights went off - obviously some trains had a different design brief
... Little Barford power station tripping at 16:52 when its declared maximum output ... dropped from 664MW to 0MW. ... Almost instantaneously, the Hornsea One wind farm (units 2 and 3) tripped, dropping its output from 756MW to 0MW, increasing the severity of the event.
So a loss of near 1½GW - not an insignificant loss of supply. From other news reports, it seems there was a lightning strike that caused Little Barford to trip - but it also triggered systems at Hornsea One which caused that to trip.
There then follows quite an interesting discussion of what happened next. The level of renewables (and interconnects) get a mention, specifically regarding their asynchronous nature. Big synchronous machines have a fair bit of mass spinning round and this helps support the grid over transients - but the level of that has been falling. It does say that the amount they had at the time "should" have been sufficient according to National Grid's previous statements.
A significant secondary effect is fingered as making the problem worse - significant amounts of embedded generation tripping as the frequency dropped quickly.
One other factor that may have added to the problem and explain the secondary drop in frequency is small embedded generators also tripping because of the sudden initial drop-in frequency. These changes have been an ongoing issue for several years with Ofgem continuing its work to make embedded generation more resilient to changing frequency events with a modification[1] being approved at the start of August. This will make embedded generation units below 5MW more resilient to Rate of Change of Frequency (RoCoF) events in the future.
I know we've had one or two discussions in here about how inverters detect loss of grid. It would appear that many of them interpreted the rapid drop in frequency as loss of grid and tripped out. It seems that this has been the subject of some work already and they are already widening the tolerances. That's fine for new kit, but I can't help thinking that few installations will get software upgrades - and given that FITs have beens scrapped for new solar PV, I think that future installs (with the relaxed tolerances) will take some time to become dominant.
The farcical situations with the trains gets a mention.
Questions also need to be asked of the non-energy sector as to why, for example, railways, took several hours to restore power ...
It seems a serious design issue if trains need an engineer to switch them back on. You'd think that power disconnections would be fairly common - eg pulling into sidings and dropping the collector pantograph/lifting the pickup shoes to disconnect from the supply while parked. I've been on a train where they were having problems, and the supervisor told us they were going to "switch it off and on again" so we didn't panic when the lights went off - obviously some trains had a different design brief
