THD (total harmonic distortion)
The overall indicator of the harmonic pollution of an electrical signal.
Definition
THD (Total Harmonic Distortion) is an indicator that quantifies the distortion of an electrical signal relative to a perfect sine wave. It is expressed as a percentage: the ratio between the RMS value of all the harmonics and that of the fundamental.
A high THD reveals a strong presence of harmonics, generally generated by non-linear loads (drives, switch-mode power supplies, LEDs). These harmonics needlessly heat transformers, overload neutral conductors and can disturb sensitive equipment.
Controlling THD is a power-quality issue; it governs the choice and sizing of transformers in a polluted environment.
The ABL tip
If your installation includes a lot of power electronics, measure the THD: a high rate calls for a reinforced transformer (see the K-factor). ABL Transfo advises you on the oversizing suited to your load profile.
