But thinking that, would it be feasible to put individual CTs over each wire (one on each phase of the generation and the consumption) and run the CT secondaries through something like a current relay, to measure the "net" of the CT secondaries??
I think that would work.
1) Wire the same ratio CTs from the same phase in opposing series so that the output equals Generation minus Consumption.
2) Swap the polarity of the Red leg from the Black leg so that the outputs from each leg are now in phase with each other.
3) Run a single wire from each of the leg CT secondaries thru the Current monitoring relay. That is a total of two wires thru the current monitoring relay sensor coil.
4) Summation of (Generation - Load)red phase + (Generation - Load)black phase. When the result is greater than zero, then the property is producing a net excess of current.
ASSUMPTIONS1) You don't need to know actual KW values. You just want to know when the property is exporting excess energy.
2) The current monitoring relay IS polarity sensitive AND it can tolerate prolonged "reverse" currents.
3) Reverse current is defined as the current it will see when consumption is greater than generation.