unbalance voltage measurement using arduino

Dear all,

I am trying to to measure un balance voltage in 3 phase ckt. The main problem is that the system is 3-phase unbalanced type. As we are not connecting neutral to the ground, there is some potential voltage at neutral which depends on the voltage of R, Y and B. So the Voltage of R phase with reference to Neutral will change if there is voltage in Y phase or B phase.

I have studied some model ,where they using schematic as below.

Can someone guide me in this circuit. where they separating ground potetial in absence of neutral.

Cadstar - Voltmeter.pdf (63.3 KB)

I'd guess that you can create a synthetic neutral (Gnd) by connecting it to the phases using 3 resistors (star topology).