True Power Factor :
In a harmonic rich network, the over all power factor of the electrical network not only depends on the displacement power factor but it also depends on the harmonic distortion in the electrical network. The true power factor is a product of displacement and distortion power factor.
The true power factor is calculated using the following formula.
True power factor = Displacement power factor * Distortion Power factor
= CosФ * 1/ (√ 1 +THD^2)
The true power factor gets deteriorate with increase in harmonic distortion. The below given table shows how the over all power factor(True power factor) is low even if the displacement power factor is 0.9.