Siemens SICAM P 7KG7750, Manual, Page: 47 / 142

3
3.2 Formulas and Calculation of Derived Quantities
47
Power Meter SICAM P 7KG7750/55, Manual
E50417-B1076-C340-A6, Edition 09.2013
Note 3
Derivation of the formula:
Total distortion D according to IEC 61000-2-2:
Equation No. 7:
u
n
: U
n
/U
1
n Order of the harmonic
U
n
Voltage of the n-th harmonic
U
1
Voltage of the fundamental component
N 40, for SICAM P: 21
M
n
Harmonic (n-th order) of voltage or current
M
1
Fundamental component of voltage or current
It is possible to derive the result from the harmonic M
1
and the RMS value M
ges
of the distorted
measured quantity. With the root „H“ from equation 8:
Equation No. 8:
M
ges
: RMS value of the distorted measured quantity U or I
M
1
: RMS value of the fundamental component of the measured quantity
Inserting the values into the equation results in:
Equation 9:
Inserting 1/M1 into the root results in:
Equation 10:
∑ ∑
= =
= =
N
n
n
N
n
n
M
M
u D
2
2
1
2
2
1
2
1
2
M M H
ges
− =
2
1
2
1 1
1 1
M M
M
H
M
THD
ges
− = =
1
2
1
2
2
1
2
1
2
− =
−
=
M
M
M
M M
THD
ges ges