I suspect that the frequency display on the dynamic demand site is not working correctly.
For some weeks it has been displaying a generally lower frequency than that displayed from other sources.
The DD meter is much quicker acting than most other sources, it is virtually real time rather than being smoothed or averaged over seconds or tens of seconds. Therefore on ANY ONE occasion, the DD meter might well be accurately displaying information that is not shown elsewhere.
However, the frequency shown on Dynamic demand is too much lower, too often, and for too long to be compatible with actuality.
Extreme load, sudden and unexpected increases in load, or sudden losses of generating/import capacity can all cause a drop in frequency. Such situations are usually handled fairly quickly with the frequency recovering in minutes, or very exceptionally in a few hours.
The national grid aim to keep the frequency within normal operational limits of 49.8 cycles up to 50.2 cycles, brief excursions beyond these limits occur fairly regularly.
The legal limits are rather wider at from 49.5 cycles up to 50.5 cycles, averaged over some short time. Excursions outside these legal limits are rare.
Any severe drop in frequency triggers automatic starting of OCGT plant and calls for extra output from other plant. If that does not relieve matters, then areas are automatically blacked out, a rare event that last occurred in August 2019, and previously about ten years before that.
I suspect that the frequency display on the dynamic demand site is not working correctly.
For some weeks it has been displaying a generally lower frequency than that displayed from other sources.
The DD meter is much quicker acting than most other sources, it is virtually real time rather than being smoothed or averaged over seconds or tens of seconds. Therefore on ANY ONE occasion, the DD meter might well be accurately displaying information that is not shown elsewhere.
However, the frequency shown on Dynamic demand is too much lower, too often, and for too long to be compatible with actuality.
Extreme load, sudden and unexpected increases in load, or sudden losses of generating/import capacity can all cause a drop in frequency. Such situations are usually handled fairly quickly with the frequency recovering in minutes, or very exceptionally in a few hours.
The national grid aim to keep the frequency within normal operational limits of 49.8 cycles up to 50.2 cycles, brief excursions beyond these limits occur fairly regularly.
The legal limits are rather wider at from 49.5 cycles up to 50.5 cycles, averaged over some short time. Excursions outside these legal limits are rare.
Any severe drop in frequency triggers automatic starting of OCGT plant and calls for extra output from other plant. If that does not relieve matters, then areas are automatically blacked out, a rare event that last occurred in August 2019, and previously about ten years before that.
