Harmonics

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

Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate (termed the fundamental frequency; usually 50 Hz or 60 Hz). Distorted waveforms can be decomposed into a sum of the fundamental frequency and the harmonics. Harmonic distortion originates in the nonlinear characteristics of devices and loads on the power system.

Harmonic distortion levels are described by the complete harmonic spectrum with magnitudes and phase angles of each individual harmonic component. It is also common to use a single quantity, the total harmonic distortion (THD), as a measure of the effective value of harmonic distortion.

--BSRIA

[edit] Related articles on Designing Buildings

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