KMB NOVAR 2600, Operating Manual

Page: 69 / 96

NOVAR 2600 Operating Manual
Measured phase voltages U
1
to U
3
correspond to the potential of terminals VOLTAGE / U1 to U3
towards the terminal VOLTAGE / N .
Three current signals - I
1
, I
2
, I
3
- are measured. Another current is calculated from samples of directly
measured ones as negative vector sum of all measured current vectors ( Kirchhoff rule ). The
calculated current is referenced as
I
PEN
. The I
PEN
value is available on a PC via communication with
ENVIS program only.
Measuring voltage inputs impedance is in range of units of MΩ. If no signal connected (for
example when protection fuse is blown), due to parasite impedance of power supply input a
parasite voltage of up to tens of volts can appear on the measuring voltage inputs. In such
case the instrument can show non-zero voltages !
5.3.1.3 Harmonics and THD Evaluation Method
Entire spectrum of harmonic components and THD is evaluated discontinuously - periodically every
second from 10 / 12 mains cycles long signal according to IEC 61000-4-7 ed.2 as harmonic sub-
groups (H
sg
).
Following quantities are evaluated :
Harmonic components of voltage and current up to 50 th order : Uih
1
, Iih
1
( i …. order of harmonic component )
Absolute angle of voltage harmonic component phasor :
φUih
1
Current harmonic component phasor angle relative to phasor Ufh
1
: φIih
1
Relative angle between correspondent voltage and current phasors : Δφi
1
Total harmonic distortion of voltage :
THD
U 1
=
1
U 1 h 1
√
∑
i = 2
40
Uih 1
2
∗ 100 %
Total harmonic distortion of current :
THD
I 1
=
1
I 1 h
1
√
∑
i = 2
40
Iih
1
2
∗
100 %
5.3.2 Power, Power Factor and Unbalance Evaluation
Method
Power and power factor values are calculated continuously from the sampled signals according to
formulas mentioned below. The formulas apply to basic type of connection – wye (star).
Active power :
P
1
=
∑
k
=
1
40
U
k ,1
∗ I
k ,1
∗ cosΔφ
k ,1
Reactive power :
Q
1
=
∑
k
=
1
40
U
k ,1
∗ I
k ,1
∗ sinΔφ
k ,1
where : k … harmonic order index, odd components only
U
k,1
, I
k,1
… the k th harmonic components of voltage and current ( of phase 1 )
Δφ
k,1
... angle between the k th harmonic components U
k,1
, I
k,1
( of phase 1 )
( these harmonic components of U and I are evaluated from each measurement cycle )
Apparent power :
S
1
=
U
1
∗
I
1
Power factor :
PF
1
=
|
P
1
|
S
1
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