Power quality monitoring in modern electric distribution systems

In electric power systems, there may be disturbances in the supply voltage and the load current drawn by a user. These disturbances happen when the frequency and amplitude are not equal to their corresponding nominal values, when there are non-sinusoidal waveforms, and when there is the presence of negative and zero-sequence components in three-phase systems. Power quality (PQ) is a generic expression used to characterize the disturbances. This paper offers an overview of the methods and instruments currently used in PQ measurements and some research activity to improve them.