Watching The National Grid for Geeks

So this is what the country’s power usage looked like over the past 7 days:


…and this is what it looked like for the past 24 hours:



…and this is what the deviations from the 50Hz median frequency looked like:

Screen Shot 2013-01-15 at 08.28.36


…all of which are available from the National Grid Realtime website; of the latter they write:

The normal system frequency is 50Hz. As electricity cannot be stored, the instantaneous generation must match the demand being taken from the system. If the instantaneous demand is higher than the generation, the system frequency will fall. Conversely, if the instantaneous generation is higher than the demand, the frequency will rise. System frequency will therefore vary around the 50 Hz target and National Grid has statutory obligations to maintain the frequency within +/- 0.5Hz around this level. However, National Grid normally operates within more stringent ‘operational limits’ which are set at +/- 0.2Hz.

Some digging around on Google suggests that the frequency shift is even more tightly controlled than that, and that ‘large’ (presumably > 0.2Hz) deviations are used to indicate peak/offpeak power availability to industry – but I can’t find anywhere confirming that yet.

Time to check wikipedia.


One thought on “Watching The National Grid for Geeks

  1. Andrew Gabriel

    Deviations in frequency represent the difference between power input to the grid, and demand. Generators (which are all in sync across the UK) start speeding up (frequency rises) if there is insufficient demand to match the power input, and conversely start slowing if the demand exceeds the power input. The power input is adjusted to meet the expected demand and the frequency should remain constant. Deviations are due to slight mismatches in the planning and reality, and unplanned events (such as a generator unexpectedly dropping off-line, and replacement input power having to be brought online to replace the missing input power).

    Some devices can monitor for low frequency, and reduce demand to help when the grid has higher demand than power input. Something like a freezer can in theory delay starting up the compressor for a while, without much impact on overall operation, until either the mains frequency rises to nearer normal, or the freezer really starts getting too warm.


Leave a Reply