ABSTRACT
This chapter discusses that harmonic waveform distortion is just one of many different disturbances that perturb the operation of electrical systems. Different nonlinear loads produce different but identifiable harmonic spectra. Utilities and users of electric power have to become familiar with the signatures of different waveform distortions produced by specific harmonic sources. Weak sources will be associated with significant harmonic distortion that can in turn affect large numbers of users served from the same feeder that provides power to the harmonic-producing customer. From the perspective of the customer, power quality means receiving a clean sinusoidal voltage waveform with rms variations and total harmonic distortion within thresholds dictated by a number of industrial standards. Even harmonics may arise if thyristor triggering angles are slightly different on every half cycle. In electric power distribution networks, harmonics due to transformer magnetizing current reach their maximum value early before dawn when the system is lightly loaded and voltage level is high.
