I have power-recording data from 11 countries (USA-60Hz mains frequency / other nation 50Hz). These data were collected using a audio recorder (in a computer) connected directly to the power mains via a step-down transformer. So, the 50hz/60Hz electrical voltage sine wave is basically stored in the computer as a .wav file.
Now if I perform a Fast Fourier Transform on these data, a distinction arises between data collected from one generator (from a grid in a country) to another in the magnitudes of their harmonics. I am including the images after performing the FFT.
Grid C I can't post 3 images due to lower than 10 reps. Thus, Grid C has no image, but the description still holds.
Here, the main 50Hz component is prominent, but the odd multiple components also are present, but not with decreasing significance. The 3rd component has the most prominence than 1st, 5th or 7th.
My question is what makes this harmonic components arise in the first place (may be some aspect of the generator). What are they dependent upon or are they arbitary? So far, from the large amount of data in my possesion, It seems that this should be a pattern of the generators it self because data from the same grid showcases this trait consistently. Can a grid (including the generators and the load) suddenly stop producing harmonics or alter their magnitudes of different harmonics?
Moreover, I can see that in Grid A, which is from USA, the harmonics are nearly absent. Where as Grid B (Lebanon) and Grid C (Turkey) have significant harmonic components. Could this be because of the better Generator and load control mechanisms of the networks of USA in comparison to those of Lebanon and Turkey?
P.S. Any information about this would be great. It would also be great if you could point out some relevant literature.