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Harmonic Calculations
These are done by 1024-point FFT (4 periods) without windowing (cf. IEC 1000-4-
7). From the real and imaginary parts, the levels Vharm and Aharm are calculated
(with respect to the RMS value of the fundamental) and the angles Vph and Aph
are calculated (phase shift with respect to the fundamental).
Vthd
The voltage harmonic level (Vharm) is multiplied by the current harmonic level
(Aharm) to calculate the apparent power harmonic level (VAharm). The power har-
monic angles are calculated from the difference between voltage harmonic angles
and the current harmonic angles.
Different Power Levels 1 Sec in Single-Phase Connection
Active power
Apparent power
Reactive power
Different Power Levels 1 Sec in Balanced Three-Phase Connection
Total Active power
Total Apparent power
Total Reactive power
U = voltage phase to phase between phase 1 to phase 2
A = phase 3
80
50
[ ]
∑
Vharm
n
=
2
=
[ ]
Vharm
1
NSS-1
1
∑
V
W
=
NSS
n
=
0
.
VA = Vrms Arms
NSS-1
1
.
∑
VAR =
NSS
n
=
or VAR = VA – W
2
3 -
W
=
3
×
NSS
3
=
⋅
U
VA
RM S
3
=
²
−
VAR
VA
or
VAR
=
3
×
50
∑
2
n
n
=
,
Athd
=
.
[ ]
[ ]
n
A
n
[
]
VF
n - NSC / 4
0
2
if computation method is with harmonics
NSS-1
∑
U
[
n
−
NSC
4 /
].
n
=
0
⋅
A
RM S
²
W
3
NSS-1
∑
UF
[
n
].
AF
NSS
n
=
0
Power Quality Analyzer Model 8230
[ ]
2
Aharm
n
2
[ ]
Aharm
1
.
[ ]
AF
n
A
[
n
]
if computation method
[
n
]
is without harmonics
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