IEEE C37.26-2014 PDF

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. Revision Standard - Active. Methods for determining the value of the power factor for inductive low-voltage (1000 V ac and lower) test circuits are provided. These methods are used in determining the power factor during short-circuit current tests in high-power laboratories. It is preferred that these methods be used during short-circuit current testing. Alternatively, other methods (including use of computerized or digital techniques) may be used, but the method used shall have been validated as producing results equivalent to those obtained using the methods in this guide. The methods described are intended for use in low-voltage test circuits (under 1000 V ac) but may also be used for higher voltages.