Total Harmonic Distortion

Total Harmonic Distortion (THD) is a specification to quantify the magnitude of the components caused by non-linear distortion of an electrical signal. It therefore indicates the ratio of the rms value of all harmonics to the rms value of the fundamental. The THD value is used in low, medium and high voltage systems. Usually, THDi is used for the distortion of the current and THDu for the distortion of the voltage.