4 ms·

I was thinking the exact same thing. I've always assumed that AC frequency wasn't exactly 50Hz and was allowed to fluctuate slightly.

• adamtulinius 9y ago
  It's supposed to average 50Hz over time, so using it for clocks make perfect sense.
• wilz 9y ago
  That assumption is right. But until now it was always compensated, so that in the mean it would be ~50hz. This correction mechanism apparently isn't enough anymore for the current fluctuations in europe.
  • TomMarius 9y ago
    Not mean, average. That's a very important distinction because if it was mean, then it might never correct, but it does.
• moccachino 9y ago
  It can be allowed to fluctuate, but still regulated to keep pretty much exactly 50Hz mean value over time.