Comment by olddustytrail

> it's about maintaining the 50hz frequency to a 0.002% accuracy (yes really)

That doesn't sound right to me. In the UK the legal requirement is to be within 1% so between 49.5 to 50.5 Hz.

In operation they aim for tighter than that at +/- 0.2 Hz, so 49.8 to 50.2 Hz, or 0.4%.

I can believe that other countries might have tighter limits but not that much!