3-36
Harmonic Options, continued
Harmonic
computation
The IEC 61000-4-7 and IEEE 519 Standards specify that the interharmonic bins
adjacent to the harmonic be included in the computation of that harmonic called
grouping, for example, if there was a 3rd harmonic (150 Hz) of 10%, and the value of
the 145 Hz bin was 1%, and the value of the 155 Hz bin was 2%, then the value
reported in the bin labelled “150 Hz” would also include contributions from the 145 Hz
and 155 Hz bins. This would give approximately 10.2%, not 10%.
The following graphs illustrate harmonic computation as per IEC 61000-4-7 Standard.
Harmonic Computation for 50 Hz
Harmonic Computation for 60 Hz
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
… 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 …
3rd harmonic
+
2 adjacent
interharmonics
4th harmonic
+
2 adjacent
interharmonics
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