**2.9. Power system harmonics**

Most of today's power system waves are distorted. By definition, "any periodically distorted waveform can be represented as a sum of pure sine waves in which the frequency of each sinusoid is an integer multiple of the fundamental frequency of the distorted wave. This multiple is called the harmonic of the fundamental." The sum of sinusoids is referred to as a "Fourier series."

In the last years, all have focused on power system harmonic distortion, because it has adverse impacts on both the utility and consumers, alike. Sometimes, when the terminology of power


**Table 1.** Electrical interruptions categorized based on their durations.

quality arises, some people routinely predict that the issue is related to power system harmonic distortion. In the past, the terms of power quality and power system harmonics have been incorrectly interchanged.
