CET iMeter 6, User Manual

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CET Electric Technology
60
4.3.2.2 Harmonics
The following table illustrates the Voltage and Current Harmonic measurements on the iMeter 6.
Phase A/AB Phase B/BC Phase C/CA
Harmonics-Voltage
THD THD THD
TOHD TOHD TOHD
TEHD TEHD TEHD
Crest-factor Crest-factor Crest-factor
2
nd
Harmonic 2
nd
Harmonic 2
nd
Harmonic
…
63
rd
Harmonic 63
rd
Harmonic 63
rd
Harmonic
Harmonics-Current
THD THD THD
TOHD TOHD TOHD
TEHD TEHD TEHD
TDD TDD TDD
TEDD TEDD TEDD
TODD TODD TODD
K-Factor K-Factor K-Factor
Crest-factor Crest-factor Crest-factor
2
nd
Harmonic 2
nd
Harmonic 2
nd
Harmonic
…
63
rd
Harmonic 63
rd
Harmonic 63
rd
Harmonic
I4 THD/TEHD/TOHD and 2
nd
to 63
rd
Harmonics
Table 4-7 Harmonics Measurements
4.3.2.3 TDD
Total Demand Distortion (TDD) is defined as the ratio of the RMS (Root Mean Square) of the Harmonic Current
to the RMS of the Rated or Maximum Fundamental Current Demand.
TDD of Current is calculated by the formula below:
where
I
L
= Maximum Fundamental Current Demand
h = Harmonic Order (1, 2, 3, 4, etc.)
I
h
= RMS Load Current at the n
th
Harmonic
4.3.2.4 K-Factor
K-Factor is defined as the weighted sum of the Harmonic Load Current according to their effects on transformer
heating, as derived from ANSI/IEEE C57.110. A K-Factor of 1.0 indicates a linear load (no harmonics). The higher
the K-Factor , the greater the harmonic heating effect.
K
max
max
h h
h
h h
h
2
1
2
1
) (
) (
h
h
I
h I
Factor


=
=
=
=
= −
where
I
h
= h
th
Harmonic Current in RMS
h
max
= Highest harmonic order
4.3.2.5 Crest Factor
Crest Factor is defined as the Peak to Average Ratio (PAR) , and its calculation is illustrated below:
x
x
rms
peak
C
=
where
|X|
peak
= Peak amplitude of the waveform
X
rms
= RMS value