Export limiting

[russellc]

I need an explanation of the export limiting CT sensing and the interface meter to the inverter. The after net metering CT sees power going to the utility or power incoming, both are just amps to it without polarity like a DC system, so how does the 'export limiting' inverter know how to limit to the grid if programmed to 'zero export' mode. Yes, I understand that when the inverter is running at full output load and more is needed the utility power has open access to feed additional power into the customer ........ As an after not relevant to this subject comment having operated large MW generating systems CT's are never left in open circuit condition. They must be shorted or on large loads they will saturate and cook and be ruined!

 

[SeaGal]

The after net metering CT sees power going to the utility or power incoming, both are just amps to it without polarity like a DC system, so how does the 'export limiting' inverter know how to limit to the grid if programmed to 'zero export' mode

The inverter measures the power flowing to or from the grid and adjusts its output power to get the reading from the CT clamp to zero. In other words it attempts to power the house load exactly, so no import or export is needed to or from the grid.

The CT in itself can only report amps, being AC - as you noted. But the amps are measured in conjunction with the instantaneous voltage (measure by the power meter or within the inverter itself) so direction can be deduced.

With a combination of measuring the amps and the volts the power (real and apparent) can be deduced.