My friend Pete reminds me that Spain, like the rest of Europe is on nominal 230v not 240v as I stated in a previous post. With an allowable variation of 10% either way that means that the supply voltage could be anything from 207 to 253 volts so when the voltage dropped to about 208 the other day triggering the alarm on my UPS, it was still within permissible limits.
Even still, if you look at that graph you can see how the voltage dropped by 20volts in the half hour period between 5:45 and 6:15pm.
Yesterday we had a series of very short power cuts one after the other which put our digibox into a funk. Probably because it had stopped, and restarted so many times within a few minutes it didn’t know where it was so I had to restart it properly to bring it back to life.