4 Design and measurement methods
31
Tab. 4. Event threshold types for individual parameters
Parameter
Interruption
Dip
Swell
Minimum
Maximum
U
RMS voltage
U
DC
DC voltage
f
Frequency
CF U
Voltage crest factor
u
2
Voltage negative sequence unbalance
P
st
Short-term flicker P
st
P
lt
Long-term flicker P
lt
I
RMS current
CF I
Current crest factor
i
2
Current negative sequence unbalance
P
Active power
Q
1
, Q
B
Reactive power
S
Apparent power
D, S
N
Distortion power
PF
Power factor
cos
Displacement power factor
tan
tan
E
P+
, E
P-
Active energy (consumed and supplied)
E
Q+
, E
Q-
Reactive energy (consumed and supplied)
E
S
Apparent energy
THD
F
U
Voltage THD
F
U
h2
..U
h40
Voltage harmonic amplitudes
(order n = 2…40)
THD
F
I
Current THD
F
I
h2
..I
h40
Current harmonic amplitudes
(order n = 2…40)
Some parameters can take positive and negative values. Examples are active power, reactive
power, power factor and DC voltage. As the event detection threshold can only be positive, in order
to ensure correct detection for above-mentioned parameters, the analyzer compares with the
threshold their absolute values.
Two parameter types: RMS voltage and RMS current can generate events for which the user
can also have the waveforms record.
The analyzer records the waveforms of active channels (voltage and current) at the event start
and end. In both cases, six periods are recorded: two before the start (end) of the event and four
after start (end) of the event. The waveforms are recorded in an 8-bit format with 10.24 kHz sampling
frequency.
The event information is recorded at its end. In some cases it may happen that event is active
when the recording is stopped (i.e. the voltage dip continues). Information about such event is also
recorded, but with the following changes:
Example
Event threshold for active power has been set at 10 kW. If the load has a
generator character, the active power with correct connection of clamps
will be a negative value. If the measured absolute value exceeds the
threshold, i.e. 10 kW (for example -11 kW) an event will be recorded
– ex-
ceeding of the maximum active power.
Summary of Contents for PQM-700
Page 85: ...85 Notes...
