A common concern in lighting is to keep THD (total harmonic distortion) at a lower level. The power supplies are nonlinear loads and therefore disturb the sinwave by introducing harmonics. These harmonics can cause interference in the operation of other electronic systems. Therefore, it is
important to measure the total effect of these harmonics. Total harmonic distortion gives us information about the harmonic content in signal with fundamental component. Higher THD means larger distortions on the input network or lower power quality.