You only need one CT. The current out of the meter is the same as the current going into the meter (where would any difference current go?).In energy meter there are 2 CT's are used.
One for recording current through incoming phase and other through outgoing phase .When the load is ON on outgoing side the current flowing through both CT's is compared by electronic circuit. An watt-meter is calibrated as per standards which measures wattage proportional to current.
by Jake Hertz
by Duane Benson
by Jake Hertz
by Duane Benson