I a have a house with 3x20A grid connection. With the usual big loads like washing machines, kitchen. For each socket in the house (many...) I want to determine the phase a wall socket is connected to in a digital way using a microcontroller telling me what phase it is on relative to another device connected to another socket (with known phase number). The result on a display could be e.g. ‘same phase’ or ‘other phase’ or even ‘lagging phase’.
I know how I would do this in an ‘analog’ way: measure current of the three grid connection phases using CT’s and switch on a significant load on the target socket and see which one responds.
But as a thought experiment I wanted to explore if there is something you can measure on the device, receive something TCP/UDP from the reference device with known phase and determine wheter it is the same phase or not. My engineering mind tells me it cannot be done since I cannot think further than a zero crossing detector with 100 crossings/s at 50Hz comparing which are only shifted >60 or <-60 degrees at 50Hz compared to the other phases, resulting in 20/6ms time difference. I then believe that is too short to receive a TCP (or UDP) reference signal to compare it to.
This is in my head as impossible for quite some time now. Just want to explore with you if you have ideas.