Operation Manual

MI 2092 Power Harmonics Analyser Section VI Theory of operation
47
Active power is divided in two quantities: Import (positive) and Export (negative).
Reactive power and power factor are divided in four quantities: positive inductive (+i),
positive capacitive (+c), negative inductive (-i) and negative capacitive (-c).
Neutral conductor current (I
0
) is ignored when measuring in 3 wire connection.
For power, voltage and current measurements, values are stored for each input cycle.
Harmonics and THD values are computed on samples of each 8
th
input cycle.
For calculation of Average Voltage, voltages less then 2 % of full scale (0.02 x U
n
) are
treated as voltage interruptions and are excluded from any calculations.
The stored maximum and minimum values are based on values calculated during each
input cycle, while average values (except for voltage, power & harmonics) are
calculated at the end of each IP and are based on the number of input cycles in the
period.
Average values for power, voltage and harmonic components ignore input cycles where
the voltage is lower then 0.02 x U
n
. Further, if a Power Break or a Power Up occurs
during an IP or the IP starts during a Power Break, the Instrument will start a new cycle
(see also Power Break recording below).
The following figures and table offer a detailed descriptions of the values used for
recording.
The meaning of abbreviations is described below.
Symbol definitions
General symbols Additional symbols
U
rms voltages
x
phase
I
rms currents
t
total
P
active power
i
inductive (with P, Q or PF symbol)
S
apparent power
c
capacitive (with P, Q or PF symbol)
Q
reactive power
+
positive (with P, Q or PF symbol)
I
0
rms neutral conductor current
-
negative (with P, Q or PF symbol)
PF
power factor
n
harmonic number (with H or h symbol)
Cosj
voltage - current phase angle
a
average (with any general symbol)
THD
total harmonic distortion
m
max. or min (with any general symbol)
H
individual harmonics (%)
na
not available
h
individual harmonic (V or A)
pn
N° of input cycles in integration period (IP)
IP
integration period
hpn
N° of input cycles for harmonics in IP (pn/8)
dPF
power factor of basic harmonic
ppn
N° of input cycles for powers
upn
N° of input cycles for voltages
PC
personal computer
cr
crest factor
pb
power break time inside IP