Harmonic analysis-frequency scan

[abrahamJP]

I am myself a newbee to Harmonic Analysis.So while after putting a simple ciruit in Cymharmo,I run impedance scan,it is showing parallel resonance for 5th harmonic.
(This software automatically calculates thevinins impedance and run impedance scan for from 60hz to 720hz).

My problem is that I dont have a 5th harmonic in load.But why software is calculating 5th harmonic and says parallel resonance exists.

please help

 

[Skogsgurra]

Resonance at a certain frequency in the transmission line and/or loads doesn't mean that you actually have a frequency component at that frequency. But, if you had, it would be amplified by the resonance.

Is this an actual installation? Or is it a tutorial example?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[lume7006]

Hello,

What your software is calculating is as you already mentioned a Thevenin equivalent of your electrical network at each of the frequencies (from 60 to 720 Hz, fundamental to 11th).
And no matter if you have loads drawing any specific harminc (5th, 7th and so on), the software gives you a "predective" answer.

One way to interpret the resonance at 5th harmonic could be:
Now, you know that if you feed any load that may draw 5th harmonic component as there is a resonance at that frequency, the electrical system (or more precisely, the switchgear where the resonance was determined) will experience problems, lets say, a high distortion in current and also in voltage.
This may cause some overheating of the conductors, transformers, etc. more losses, and so on.
Of course, this will depend on the level of harmonics, to verify it, I recommmend you to take a look at IEEE Std 519, which is the base for limits.
And also there are some tutorials at IEEE, some text books like Dr Arrilaga, Mr McGranagan.