## 11/01/2020

### Effect of Harmonics on Power Factor

Effect of harmonics on Power Factor
• It is defined as the ratio of cosine of voltage vector and current vector.
OR
Power Factor = kW / kVA
Displacement Factor ( Displacement Power Factor )
• It is defined as the Cosine of angle between voltage vector and current vector at the fundamental frequency.
Displacement Factor = P / V1I1
Distortion Factor ( Distortion Power Factor )
• The power factor in which effect of harmonic of the system is considered is called as distortion power factor
• It is ratio of fundamental RMS current to the RMS current of the total current.
Distortion Factor = I1 / I
= 1 / √ ( 1 + THD2 )
Where I1 = Fundamental current
• Higher the value of total harmonic distortion, lower the distortion power factor
True Power Factor
• It is defined as the ratio of average power to the apparent power.
True power factor = P / VRMSIRMS
= Displacement Factor × Distortion Factor
Capacitor banks
• The improvement of the power factor is done by capacitor bank and in this case improvement done in the displacement power factor.
• The voltage and current waveform are at the fundamental frequency or say at 50 Hz.

Effect of harmonics on Power Factor
I = I1 √ ( 1 + THD2 )
• The kVA demands increases due to increase in RMS current but the kW output of the system does not change.
kVA = kW / Power Factor
• The power factor has to decrease if the kVA demand increases with kW remain unchanged.
• This power factor decrease due to presence of harmonics.
• The true power factor remain low in spite of displacement power factor increases due to poor distortion power factor
True power factor = Displacement Power Factor × Distortion Factor
Capacitor bank and Distortion power factor
• The capacitor bank do not significantly improve distortion power factor.
• It can lead to harmonic resonance and harmonic amplification when harmonic present in the system.
• The harmonic amplification is avoided by using detuned reactors.
How to increase true power factor?
• The true power factor is increased only if both displacement power factor and distortion power factor increases.
• The capacitor bank improves displacement power factor.
• The active harmonic filter must be used to improve distortion power factor in a system which consists of rich harmonics.
• The combination of capacitor and active harmonic filter is good combination for power factor improvement.
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