Waveform distortion noise

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

Noise is unwanted electrical or electromagnetic energy that can degrade the quality of signals and data. Noise occurs in digital and analogue systems, and can affect files and communications of all types, including text, programs, images, audio, and telemetry. Digital clocks can sometimes run extremely fast.

In a hard-wired circuit such as a telephone-line, external noise is picked up from electrical transformers, control circuits, arcing equipment, loads with solid-state rectifiers, and switching power supplies, from the atmosphere, and even from outer space. Noise problems are often exacerbated by improper earthing that fails to conduct noise away from the power system. Normally this noise is of little or no consequence. However, during severe thunderstorms, or in locations where many electrical appliances are in use, external noise can affect communications. In data communications it slows down the data transfer rate, because the system must adjust its speed to match conditions on the line. In a voice telephone conversation, noise rarely sounds like anything other than a faint hissing or rushing.

--BSRIA

[edit] Related articles on Designing Buildings

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