Measurement of reactive power using a 90/spl deg/ reference and a wattmeter

A reference standard for VARs is described which uses a calibrated wattmeter with applied voltage displaced by 90/spl deg/ from that of the VARmeter under test. Precise quadrature between the two voltages is monitored using a variation of the NML zero power-factor reference described previously. The uncertainty in VAR measurement is significantly better than that achieved by calculating from watts and apparent power.