A study on the feasibility and effectiveness of digital filter application for harmonic and interharmonic measurement in compliance with IEC 61000-4-7

Large scale monitoring of power quality in electrical power plants is nowadays a pressing need due to the liberalization of the electrical market in many countries and the deeper interconnections of electrical networks. Many instruments are today available on the market. Even if they provide good accuracy and measurement capability, they are generally developed for single point measurements. Their use in large scale monitoring leads to high costs. In this framework research activity, the authors aim at the realization of a measurement instrument for power quality monitoring in compliance with IEC 61000-4-30 and 61000-4-7 standards capable of granting good accuracy, satisfying repeatability, and cost effectiveness since the use in large scale monitoring is allowed. In this paper the attention is paid to the measurement algorithm to be adopted. The use of an alternative measurement approach with respect to the FFT one is proposed. Digital filters shaped on the harmonic group are thoroughly optimized for grouping measurements required by the IEC EN 61000-4-7 standard both in simulation and emulation environments. The obtained results confirm the advantages of the proposal.