What is the correct way for a 3 Phase Watt-Hour meter to measure total import/export watt-hours?
I ask because I have seen this done in 2 different ways both in 'approved' meters:
Red Phase - importing 1kW
White Phase - importing 2kW
Blue Phase - exporting 1.5kW
Assume this is constant for 1 hour.
What should the Watt-Hour register record?
Option A - Add up phases before adding to totaliser:
1 + 2 - 1.5 = 1.5 kWh Imported
Option B - Add import to import, export to export:
1 + 2 = 3 kWh Imported AND 1.5kW Exported
I have seen meters and solar-loggers use option A and more recently meters doing option B.
What is 'right'? I can't seem to find where this calculation is specified in IEC 62053 - but I don't have $1000 to spend getting each part of it, which may or may not have the calculation specified.