IEEE 519-2014 Recommended current distortion limits

[Farid_Kadri]

Hi there,

In IEEE 519-2014, we can see in §5.2 the recommended current distortion limits for systems nominally rated 120 V through 69 kV which depends on short circuit ration (I_SC/I_L), these maximum harmonics current distortion are expressed in percent of IL.

For example, for 50 < I_SC/I_L < 100; 3 ≤ h <11 - HD = 10% and 11≤ h < 17 - HD = 4.5% …. (HD is Harmonic Distortion).

My question is the following: are these harmonic distortion limits found based on calculations (formula) or it’s just empiric values based on experience?