geoffreycoan Physically there is always going to be one CT clamp installed just ahead of the other on the meter tail. Whether you could do something more clever with boards and sub-boards and clamps in different positions across the boards, I don’t know.
Yes, but if they're on the same cable (topologically), they're measuring the same current.
Perhaps I can illustrate with my EVSE wiring: before and after
The GE is off to the lower left, and the house load (red/black tails) is off to the top-left. Smartmeter is at the top, with isolator to the right of it. Mini CU for the Zappi is on the bottom-right. The CT on the cable going into the meter is for the Zappi. The one after the isolator switch is for the GE. Even though they were on physically different cables, in the before picture, all the load went through both cables, and so both reported all activity. In particular, the GE was aware of the load the Zappi was drawing overnight, and wanted to discharge to cover it.
By adding a second splitted block, the GE clamp is now on the loop between between the two blocks. So GE now does not see any load from the Zappi.
With a similar sort of arrangement, one hybrid inverter would see everything to/from the grid, whereas the second would see only downstream of the first. Both see the house load.
To give a concrete example, consider cross-charging. In the case that both are measuring the actual grid connection, one starts charging and the other discharges to cover it. One that's charging sees that there is no grid activity, and believes it's doing the correct thing in consuming unused export. The one that's discharging sees that what it's generating is not going to the grid, and so believes it is covering house load, and is happy. This is a stable state.
For the explicit separation case: lets call the "primary" inverter the one that's measuring the real grid connection, and the "secondary" one the downstream one. Suppose secondary started cross-charging from the first. The primary believes it is covering house load, and so is happy to continue. But the secondary perceives that it is drawing from "grid", and so stops.
Or if you were to force-discharge from the primary, the secondary wouldn't see it, and so has no reason to consume it, and it would go to the grid as (presuambly) intended. You do of course have the problem that if the secondary force-discharges, the primary will consume it unless told not to.
If the secondary is spills excess solar that wouldn't fit in its battery, the primary will consume it. But unfortunately, it wouldn't work the other way round, since the secondary would not see power spilled by the primary. Would probably need some sort of invervention to manage that case.
