We regularly have brief power cuts which trigger my uninterrupted power supply into action. The UPS either keeps my computer and monitor working until power is restored or it shuts the computer down properly if the delay is beyond the capacity of the battery.
This morning however my UPS kicked into action three times within a few minutes. When I investigated, it seems we hadn’t suffered a power cut, this time the voltage had dropped so low that the UPS changed to battery backup to prevent any problems. Looking at the graph, the voltage had dropped from its nominal 235 to below 220.
Remember that when we came back from England, the voltage had been peeking at 250 volts, a level at which certain circuit boards can fry. Now it is running at 235 volts and dipping down to 220 volts. Maybe it was a coincidence that many of the residents got up just at that point and put the kettle on for a morning cuppa, no lo se!