At about 03-00 today I had another power cut, this happens fairly regularly and is not normally worthy of much comment.
However I noted that after the supply was restored, that the UPS was still making unhappy sounds due to "mains out of tolerance"
I then observed the "dynamic demand" website, upon which there is a real time display of UK grid frequency. This looked very unstable with the frequency "bouncing around" a great deal.
There was nothing remarkable about the actual frequency attained, it remained generally within the usual operating limits of 49.8 cycles to 50.2 cycles.
What was however most exceptional was the speed of the frequency variations, less than a second for a 0.3 cycle change, and the number of these sudden frequency changes, at least a dozen such rapid changes in a minute.
I then observed the national grid website "frequency for the last 30 minutes" chart. This showed nothing unusual, but I suspect that the chart has insufficient resolution to display frequent and very brief events.
