Current THD limits at the PCC
A change was made to the Current distortion limits table to document what has been practiced in the field for many years - limiting the assessment of harmonic currents up to a maximum of the 50th harmonic. This is accomplished by clearly stating in Table 2 of IEEE Std 519-2014; the maximum individual harmonic range is 35th < h < 50th .
Voltage THD limits at the PCC
Table 11-1, Voltage distortion limits, in the 1992 version was updated (Table 1 in the 2014 version) with the addition of a new voltage range and limits.
A new lower PCC voltage range of V < 1.0 kV was defined, with higher allowable harmonic voltage limits: Individual harmonic at 5% and Total harmonic distortion at 8%. These limits are higher than the next highest voltage range 1.0 kV < V < 69 kV.
High-frequency Current Allowance in Low Current Distortion Systems
IEEE 519-2014 provides for an allowance of higher high-order harmonic current limits at a PCC that has low lower-order harmonics. The allowance is applied to Table 2, Current distortion limits, if a prescribed minimum performance level is met. For example, if a power system with Isc/IL< 20 has 5th and 7th harmonic currents at< 1%, then all other harmonic limits in Table 2 may be exceeded up to a factor of 1.4 and still be in compliance.