There are devices that detect when your PV panels are exporting power to the grid - so that you can divert it to heat water or a thermal store, for example.
These rely on a sensor that clips around one of the conductors at the grid connection.
Can anybody explain to me, in simple terms, how this is achieved with AC? I can understand measuring the magnitude, but not the direction.
I'm sure it's obvious, but I may have dissolved the necessary part of my brain over the years.