Simple Arduino Home Energy Meter
Three-phase is simply three single phases, so not really more difficult. You need three of this instructables' devices to read your 3 three phase lines. You also need to scale your CTs(turns ratio), resistors(impedance value) and the code for 400vac. You could possibly combine the power readings onto a fourth LCD displaying an overall power usage and phase angles of the three phases (and the code to do it). All that said you very much need to know what type of 3ph you have, Delta or Wye, for proper grounding of the Arduino circuit(s). I recommend Noobs stick with single-phase until mastering it before attempting three-phase metering projects...remember safety first always and have an assistant standing by to kill the main breaker! Hope this helps.
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