Technical description
4 Measurement functions
4.8 Power calculations
VM50.EN004
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4.8.
Power calculations
NOTE! These calculations is available when voltage measurement mode is 1LL
(line-to-line voltage, see Figure 8.10.2-2) or 1LN (phase-to-neutral
voltage, see Figure 8.10.2-3).
The power calculations in the VAMP 52 are dependant on the
voltage measurement mode. The formulas used by the VAMP
52 for power calculations are found in this chapter
Line to line voltages measured (1LL mode)
As the device is measuring U
12
only, the U
23
voltage is
calculated by assuming that voltages are symmetrical.
12
23
2
120
1
U
a
U
a
3
23
1
12
*
*
L
L
I
U
I
U
S
where,
12
U
= Measured line voltage L1-L2 phasor, fundamental
frequency component.
1
*
L
I
= Complex conjugate of the measured phase L1
current phasor.
23
U
= Measured line voltage L2-L3 phasor, fundamental
frequency component
3
*
L
I
= Complex conjugate of the measured phase L3
current phasor.
S
P
S
imag
Q
S
real
P
cos
)
(
)
(
Phase to neutral voltages measured (1LN mode)
Active power calculation for one phase:
cos
1
1
1
L
L
L
I
U
P
Reactive power calculation for one phase:
sin
1
1
1
L
L
L
I
U
Q
where,
U
L1
= Measured L1 phase voltage
I
L1
= Measured
L1
current
= Angle between U
L1
and I
L1