A new current-comparator-based high-voltage low-power-factor wattmeter

Abstract

A current-comparator technique is applied to power measurements for obtaining a highly accurate high-voltage low-power-factor wattmeter. The instrument has two time-division-multiplier-type wattmeters. One wattmeter, in conjunction with a digital signal processing block, is used to provide automatic balancing of the quadrature component of the load current in a current comparator against a quadrature current from a high-voltage quadrature current reference source. The other wattmeter is used to measure the residual loss component of the load current. This new current-comparator-based high-voltage low-power-factor wattmeter has an order of magnitude improvement in accuracy, and a lower power factor measuring range, than a previously developed instrument. It has an estimated uncertainty with respect to its readings of less than 0.02% at 0.1 power factor and higher, 0.2% at 0.01 power factor, 0.5% at 0.001 power factor, and 5% at 0.0001 power factor. In addition to power, the high-voltage low-power-factor wattmeter measures source voltage, current, power factor, and reactance of the load. © 1999 Canadian Crown Copyright.