Revision Standard - Active.
Definitions used for measurement of electric power quantities under sinusoidal, nonsinusoidal, balanced, or unbalanced conditions are provided in this standard. Mathematical formulas for measurements and the appropriate notations for expressing quantity values are given. Informative annexes discuss (A) the measurement observation period, (B) combining Fourier decomposition and phase-sequence components, (C) a systems approach to measurement, (D) filtering, (E) a Trust Metric and a No-trust Metric, (F) Source Apparent Power, and (G) omissions from the previous version of Std 1459. Expressions that were used in the past, as well as new expressions, are listed, as well as explanations of the features of the new definitions. An errata for this PDF is available at: https://standards.ieee.org/wp-content/uploads/2025/06/1459-2025_errata.pdf