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Grid problem ?

broadgage
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.
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    Hi Dave, I'm not saying anything about how they measure it, just that we do not know quite what they do, and I must admit I find the idea that the whole grid is speeding up and down at some hundreds of milli-Hz per second is surprising, given that even a small diesel rig is normally more stable than this, and I am concerned that some of the reported jitter may be an artifact of their method. It is obvious from their website that their freq measurement is home made,

    Here at Dynamic Demand, we built (at very little cost) a device that continuously monitors the frequency on the electricity grid and updates this website with real-time data.





    My caution is that there are subtleties to doing this sort of thing that some of us may well be  aware of, including AM to PM conversion due to zero crossing offsets, proper suppression of noise by choice of tracking loop filter etc, that they may or may not be correctly taking into consideration.

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    Hi Dave, I'm not saying anything about how they measure it, just that we do not know quite what they do, and I must admit I find the idea that the whole grid is speeding up and down at some hundreds of milli-Hz per second is surprising, given that even a small diesel rig is normally more stable than this, and I am concerned that some of the reported jitter may be an artifact of their method. It is obvious from their website that their freq measurement is home made,

    Here at Dynamic Demand, we built (at very little cost) a device that continuously monitors the frequency on the electricity grid and updates this website with real-time data.





    My caution is that there are subtleties to doing this sort of thing that some of us may well be  aware of, including AM to PM conversion due to zero crossing offsets, proper suppression of noise by choice of tracking loop filter etc, that they may or may not be correctly taking into consideration.

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