9-3
IM WT3001E-51EN
IEC Harmonic Measurement (Option)
9
• Harmonic Subgroup
A harmonic and its two directly adjacent interharmonics are collectively called
harmonic subgroup. The computing method to combine the harmonic and its two
adjacent interharmonics is not simple addition, but the square root of the sum of the
square of each component.
Figure when the fundamental
signal is 50 Hz
Harmonic subgroup
• Harmonic Group
A harmonic and its adjacent interharmonics are collectively called harmonic subgroup.
The computing method to combine the components is the average of the sum of the
squares as with the harmonic subgroup. A half of the amplitude is included for the
interharmonic that is in the middle of two orders.
Figure when the fundamental
signal is 50 Hz
Harmonic group
Include a half of the amplitude
Figure when the fundamental
signal is 60 Hz
Harmonic group
• Grouping of Harmonics in IEC Harmonic Measurement
There are three types of grouping of harmonics in IEC harmonic measurement. The
method to calculate the amplitude of the rms value of the harmonics varies depending
on the grouping method.
• No Grouping (OFF)
Only the components of the integer multiples of the fundamental wave are
considered harmonics. Therefore, interharmonic components are not included.
• Grouping Type 1
The harmonic subgroup is considered a component of the corresponding order.
Therefore, harmonics take on a larger value when harmonic subgroups are
included in the input signal as compared to when grouping is turned OFF.
• Grouping Type 2
The harmonic group is considered a component of the corresponding order.
Therefore, harmonics take on a larger value when harmonic groups are included in
the input signal as compared to when grouping is turned OFF.
9.1 IEC Harmonic Measurement Function
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