IEEE C37.26 2014 Edition, August 21, 2014
Guide for Methods of Power-Factor Measurement for Low-Voltage (1000 V AC or lower) Inductive Test Circuits
This guide describes three methods used in the measurement of the power factor of inductive low-voltage (1000 V and lower) test circuits. These methods may be used at any frequency; however, the values in the tables are specifically for 60-Hz test circuits. These methods are as follows:
a) Ratio method
b) DC decrement method
c) Phase relationship method
Table 1 lists the preferred methods to be used for different levels of test currents and for different levels of power factor. While this guide is primarily intended for use on low-voltage test circuits, the methods discussed are also usable at higher voltages.
The purpose of this guide is to recommend methods of measuring the power factor for inductive test circuits, so that the preferred method giving the greatest accuracy is recommended for any particular circuit.