Power measurements in distorted and unbalanced conditions-an overview of IEEE Trial-Use Standard 1459-2000

The definitions and formulas used today for common power system measures such as active, reactive, and apparent power have been in use since the 1940´s. When these definitions were developed, loads were dominated by motors, lighting and other linear loads. Simplifications in calculations could then be made by taking advantage of the assumption of relatively balanced and non-distorted voltages and currents. Times have changed. Power electronic devices such as computer power supplies, phase controlled rectifiers, static VAr systems, cycloconverters, and other nonlinear, harmonic producing loads dominate today´s loads. Also loads are more dense in commercial environments and due to the increased loads being added in an unplanned fashion in individual office environments, the assumptions regarding balanced loads are less valid than before. This paper summarizes how the new IEEE 1459 Trial-Use Standard addresses these issues with mathematically rigorous, yet useful and often intuitive definitions for power related quantities under sinusoidal, nonsinusoidal, balanced or unbalanced conditions.