In the balanced three phase power measurement using two wattmeter method, each wattmeter reads 20 kW when the pf is unity. What does each wattmeter reads when the pf falls to (i) 0.6 lag and (ii) 0.573 lag. The total three-phase power remains unchanged.

According to Blondel's theorem, the total power is measured with one less number of wattmeters than the number of wires present in the system. So, a single-phase and two-wire system will require one wattmeter and a single-phase and the three-wire system …