The Western Power (WA) Rules
This is how Western Power officially describes how their meter works...
"The 3 phase meter measures the combined consumption and
generation across all three phases continuously - it does not distinguish
between phases and then takes the net after a set period (of 10 minutes).
If there is excess generation on one phase, and a load on another phase,
then the excess generation will supply that load. If there is still more power
required, then the customer will receive electricity from the network and it
will be recorded in the meter as purchased/imported electricity. But if
there is still excess generation after supplying all of the household load,
it will be sent out onto the network and recorded as sent out (or exported
onto the network), which is where the customer receives REBS and/or FiT
(or neither if they aren't eligible)."