Measure 208v single phase with Current Transformer
If you are sure there is not a ground fault (i. e. current flowing through the ground wire), then all current flowing through one leg must also flow through the other. Therefore, it is sufficient to measure only one leg.

If you are not sure about ground current and don't have a GFCI on the circuit, you would need an additional current transformer, either on the ground wire or the other leg.