Interharmonics

BSRIA Power quality guide (AG 2/2000) was written by C C Pearson and V Uthayanan and published by BSRIA in July 2000. It states:

Waveform distortion is defined as a steady state deviation from an ideal sine wave of power frequency, principally characterised by the spectral content of the deviation.

There are five primary types of waveform distortion:

• dc offset
• harmonics
• interharmonics
• notching
• noise

Voltages or currents having frequency components that are not integer multiples of the frequency at which the supply system is designed to operate (e.g. 50 Hz or 60 Hz) are called interharmonics. They can appear as discrete frequencies or as a wide-band spectrum.

Interharmonics can be found in networks of all voltage classes. The main sources of interharmonic waveform distortion are static frequency converters, cyclo-converters, induction motors and arcing devices. Power line carrier signals can also be considered as interharmonics.

The effects of interharmonics are not well known. They have been shown to affect power line carrier signalling, and induce visual flicker in display devices such as CRTs. They also have the same effects as harmonics of similar magnitude, the only difference being that their frequency is not in the harmonic series.

--BSRIA

[edit] Related articles on Designing Buildings

• Alternating current and direct current
• Ampere.
• BSRIA articles on Designing Buildings.
• BSRIA definitions.
• BSRIA.
• DC offset.
• Harmonics.
• Power.
• Triplen harmonics
• Voltage.
• Watt.