Understanding Harmonics in Electrical Power

[Abdul Wali]

Hi, please help me with the following questions !
can we say that harmonics are because of Reactive Power (i know that one way of controlling harmonics is filtering) ? IF YES, can we control Reactive power by increasing Power Factor ? IF YES it means Harmonics can be controlled by increasing Power Factor ? Does Harmonics occurs by supplying a pure DC current to non linear load ?

 

[anorlunda]

See
https://www.physicsforums.com/insights/ac-power-analysis-part-1-basics/
https://www.physicsforums.com/insights/ac-power-analysis-part-2-network-analysis/

But the short answer is that VARs and power factor have nothing to do with harmonics. You seem to be confusing two concepts.

 

[jim hardy]

anorlunda is right.

Harmonics in electrical power discussion come about when something departs from a sine wave.
Read up on Fourier Analysis
any continuous repetitive waveform can be expressed as a sum of sinewaves of different frequencies
that of the basic wave that's repeating itself
plus all its harmonics, each multiplied by a proportioning coefficient and shifted in phase

The electric company goes to a lot of trouble to keep the sinewave pure
but harmonics creep in.

Start with this wiki article
https://en.wikipedia.org/wiki/Harmonic_analysis
two images from it:
here's the waveform of a bass guitar string making a 55 hz A note

and a plot of its Fourier Analysis

each peak is a harmonic, observe 55hz(first) 110hz(second, and as expected pretty small) 165(third) 220(fourtg) and so on.

That's the simplest concept of harmonics. Deviation from a sinewave and "Dr Fourier's Painless Transform"..

There are small portable instruments that display the Fourier Analysis of a signal. They are really handy for maintaining rotating machinery because the harmonic content of a vibration signal tells you a lot about what's going on in the machine.

I hope that helps with the concept.