Operation Manual

MI 2092 Power Harmonics Analyser Section II Internal operation
16
Section II Internal operation
1. Introduction
This section contains technical information on the internal operation of the Power
Harmonics Analyser, including descriptions of measuring methods and recording
principles.
2. Measurement methods
Measurement methods are based on the digital sampling of the input signals. Each
input (3 voltages and 3 currents) is sampled 128 times in each input cycle. Duration of
this input cycle depends on the frequency at the synchronization input (one of the 3
voltage inputs or a current input). At 50 Hz, the input cycle period is 20ms.
Basic measured values are calculated at the end of each sampling period and the
results are available on the display or are recorded.
FFT based results are only calculated on every 8
th
input cycle (every 160ms@50Hz).
The following equations are used for computing the given quantities.
Basic calculations
Parameter Equation for calculation Unit Formula N°
Phase voltage
U
u
x
x
i
i
=
=
å
1
128
2
1
128
V [1]
Phase current
Ii
xx
i
i
=
=
å
1
128
2
1
128
A [2]
Phase active power
Pui
xx
i
x
ii
=*
=
å
1
128
1
128
W [3]
Phase to phase voltage
()
U
u
u
xy
x
y
i
ii
=-
=
å
1
128
2
1
128
V [4]
Neutral conductor current
Iiii
iii
i
0123
2
1
128
1
128
=++
=
å
()
A [5]
Additional calculation (using basic values)
Phase apparent power
S
U
I
x
x
x
=
*
VA [6]
Phase reactive power
QSP
xxx
=-
22
var [7]
Phase power factor
PF
P
S
x
x
x
=
[8]