IEEE Power Engineering Review

Models for power system components are important nor only for calculating power quality indexes but also for understanding the propagation characteristics of the disturbances. There are several types of power quality disturbances. The disturbances are typically classified according to their duration and frequency content. The voltage sags, for example, cause reduction on RMS, values for a few cycles. The harmonics, on the other hand, result in sustained waveform distortions. Accordingly, the responses of power system components and their associated models can be quite different for different disturbance types. In this article, we concentrate on the three most common disturbances: harmonics, transients and sags/swell, with the harmonics as the main focus . The modeling subject can also be divided according to the types of power system components. The most common components encountered for power quality analysis are overhead lines, underground cables, transformers, rotating machines, power electronic devices, aggregate loads, and external systems. Models related to these components include: harmonic analysis, which is mainly based on frequency domain; transient analysis, which is mainly based on time domain; and sag/swell analysis, which is mainly based on phasors (frequency-domain at 60/50 Hz). Each of these models is discussed in this article.