Electric Power Quantities in the Presence of Harmonics - A Case Study

This paper analyzes electrical power quantities obtained by different power theories and measurement methods in the presence of harmonics. In this case, the power factor is significantly reduced, and the correct measurement of power and energy is challenging. International standards do not specify accuracy requirements for power and energy meters under non-sinusoidal conditions, and their accuracy is therefore questionable. On the other hand, penalization of low power factor operation and power factor correction are based on power and energy measurement. The guidelines for power measurement under non-sinusoidal conditions can be found in IEEE 1459 and are rarely used in practice. In this paper, a case study is carried out with measured data from an industrial plant where high harmonic distortions of current and voltage are present and active harmonic filters are installed. From the measured voltages and currents under sinusoidal and non-sinusoidal conditions, the electric power quantities are calculated according to IEEE 1459, the Budeanu theory, DIN40110, and two methods used by typical power meters: the quarter-cycle voltage delay method and the integral voltage phase shift method. The results have shown that typical power meters are subject to significant errors under industrial conditions. In addition, the electric power quantities determined by different power theories and standards can vary significantly under non-sinusoidal conditions.