We have touched this subject before, but as the threads are so long I've started a new.

The European voltage is often referred to as 230 +/10%. Simple enough, right? Wrong. In reality there is a European standard, EN 50160 for how the voltage is to be measured.

The requirements is +/-10% for at least 95% of the time. The remaining 5% of the time, it's +10/-15%. (253-195.5V)

Wait, it gets worse. You can't just take the instant readings, as dips and surges sends the voltage outside the interval. As these doesn't harm the appliances an average over time is taken. This would have been fine, had it not been for the fact that the standard calls for a 10 minute average. A miswiring can send 400V to the users, but as long as the problem is fixed within a minute or so the voltage is still within specifications.

Would you be surprised to know that it is the utilities who are behind this standard? [Linked Image]

We should also not forget that there is a voltage drop in the installation (3-5%). Hence, in a worst case situation the voltage at the outlet can be 230V - 20% = 184V...