A history of harmonics in power systems

Waveforms of potential (voltage) and current in electric power systems are seldom the idealized functions on which engineering work is based. Harmonic analysis can be used to resolve complex time-based waveforms into spectral components. History teaches us that as new problems with harmonics arise, new instruments to measure the phenomenon will be offered and tighter limits on allowable deviations will probably be pushed. The old problems return to take on new forms.