Thanks for that info pauluk.
Was your area affected too ?
We have similar problems here soon in NZ. Hydrolevels low, profits up and not enough thermal capacity at the moment.
I will post when D day arrives in about 3 to 4 weeks.
Regards, Raymond
We weren't affected where I am, although it seems that some towns in Suffolk (next county to the south) were blacked out, and there were also failures in mid-Lincolnshire (next county north/northwest).
Reading from various sources, it seems that what happened is that the Longannet power station (about 2400MW capacity) up in Fife, Scotland, had an unexpected shutdown, and this was followed within 2 minutes by another unexpected shutdown of Sizewell B nuclear in Suffolk (about 1200MW).
The resulting loss of capacity brought in automatic load shedding to stabilize the network. Somebody on the IEE forum noted from UPS logs and the National Grid's realtime network page that the grid frequency had dropped right down to 48Hz.
The under frequency relays at least worked OK.
In NZ they are set to 47.8 Hertz for selected feeders and 47.5 Hertz for all feeders in substations of the local POCO Auckland distribution network, to avoid a complete blackout.
We tested all our UF relays about 2 months ago in preparation for an interesting wintertime with low hydro levels.