Propagation of Supraharmonics in the Low Voltage Grid

The frequency range above 2 kHz has in the past been considered as “high frequency” for the power quality community whereas frequencies below 150 kHz have been considered as “low frequency” for those working with EMC issues. The term “supraharmonics” has been proposed for any distortion in this frequency range and the term is getting more and more used.

An increasing amount of equipment emits non-negligible levels of supraharmonics in the grid. Also voltage distortion in this frequency range has shown to be nonnegligible at certain locations.

The distinction between primary and secondary emission is very important for studies on supraharmonics. A consistent set of definitions for primary and secondary emission has been developed as part of this project. A third phenomenon, interaction, is introduced in which the non-linear properties of two or more devices impact harmonic or supraharmonic voltages and currents.

Measurements performed have shown that supraharmonics can have a serious impact on the light intensity of LED lamps. This is a new phenomenon and may be an as yet unknown source of light flicker.

The reduction of emission in the lower-frequency ranges (harmonics) appears to result in an increase in supraharmonic emission by equipment. Setting more strict requirements on harmonic emission may have the unintended consequence of an increase in supraharmonic levels.

Both measurements and simulations have shown that resonances play an important role in the spread of supraharmonic distortion through the low-voltage network.