Harmonic distortion and voltage spike calculations

Harmonic currents and voltages calculations in power system have traditionally been carried out either using `hand´ calculations or using computer program which have been developed from fundamental frequency load flow program. The common features of these two methods is that they are both frequency domain calculations and also rely heavily on assumed data from manufacturers about the harmonics generated by their products. In the case of electric drives this information is often in the form of a look-up table. Here, the author discusses the limitation of such methods. He suggests that for many systems a time domain approach to harmonic distortion calculations is needed and that a fuller representation is often needed especially for low voltage system where the concept of an infinite busbar or a fixed harmonic load are no longer valid. The approach described is based on experience gained on offshore oil platform electrical system and ship electrical systems