MI 2893 / MI 2892 / MI 2885
Measurement methods
192
Total voltage harmonic distortion:
2
40
2
1
n
p
n
p
p
U
h
U
h
U
THD
, p: 1,2,3
(60)
Total current harmonic distortion:
2
40
2
1
n
p
n
p
Ip
h
I
h
I
THD
, p: 1,2,3
(61)
Spectral component between two harmonic subgroups are used for interharmonics assessment. Voltage
and current interharmonic subgroup of n-th order is calculated using RSS (root sum square) principle:
n
th
voltage interharmonic:
8
2
2
)
10
,(
k
k
n
C
n
p
U
ih
U
p: 1,2,3
(62)
n
th
current interharmonic:
8
2
2
)
10
,(
k
k
n
C
n
p
I
ih
I
p: 1,2,3
(63)
50
100
150
200
Uc,k
Uh
1
Uh
2
Uh
3
Uh
4
Freqency
Uih
1
Uih2
Uih3
Figure 157: Illustration of harmonics / interharmonics subgroup for 50 Hz supply
The K factor is a factor that is developed to indicate the amount of harmonics that the load
generates. The K rating is extremely useful when designing electric systems and sizing components. It is
calculated as:
K - factor:
50
1
2
50
1
2
)
(
n
n
p
n
n
p
p
h
I
n
h
I
K
, p: 1,2,3
(64)
5.1.9
Signalling
Standard compliance: IEC 61000-4-30 Class A (Section 5.10)
Signalling voltage is calculated on a FFT spectrum of a 10/12-cycle interval. Value of mains signalling
voltage is measured as:
RMS value of a single frequency bin if signalling frequency is equal to spectral bin frequency, or
