MI 2792 PowerQ4 Plus
Theory and internal operation
111
U
Swell
– maximum swell magnitude voltage is the largest U
Rms(1/2)
value measured
on any channel during the swell.
The start time of a swell is time stamped with the time of the start of the U
Rms(1/2)
of the channel that initiated the event and the end time of the swell is time
stamped with the time of the end of the U
Rms(1/2)
that ended the event, as defined
by the threshold.
The duration of a voltage swell is the time difference between the beginning and
the end of the swell.
Voltage interrupt
Standard compliance: IEC 61000-4-30 Class A & S (Section 5.5)
Measuring method for voltage interruptions detection is same as for dips and swells,
and is described in previous sections.
The interrupt threshold is a percentage of nominal voltage defined in Voltage events
setup menu. The interrupt threshold can be set by the user according to the use.
Instrument permits interrupt evaluation:
On single-phase systems, a voltage interruption begins when the U
Rms(1/2)
voltage
falls below the voltage interruption threshold and ends when the U
Rms(1/2)
value is
equal to, or greater than, the voltage interruption threshold plus the hysteresis
(see Figure 5.8),
on polyphase systems two different evaluation techniques can be used for
evaluation simultaneously:
o
a voltage interruption begins when the U
Rms(1/2)
voltages of all channels fall
below the voltage interruption threshold and ends when the U
Rms(1/2)
voltage on any one channel is equal to, or greater than, the voltage
interruption threshold plus the hysteresis.
o
a voltage interrupt begins when the U
Rms(1/2)
voltage of one channel fall
below the interrupt threshold, and ends when the U
Rms(1/2)
voltage is equal
to or above the interrupt threshold plus the 2% of hysteresis voltage, on
the same phase.
A voltage interrupt is characterized by a pair of data: minimal interrupt voltage
magnitude, and duration:
U
Int
– minimum interrupt magnitude voltage is the lowers U
Rms(1/2)
value measured
on any channel during the interrupt.
The start time of a interrupt is time stamped with the time of the start of the
U
Rms(1/2)
of the channel that initiated the event, and the end time of the interrupt is
time stamped with the time of the end of the U
Rms(1/2)
that ended the event, as
defined by the threshold.
The duration of a voltage dip is the time difference between the start time and the
end time of the voltage dip.
5.1.13 Alarms
Generally alarm can be seen as an event on arbitrary quantity. Alarms are defined in
alarm table (see section 3.16.3 for alarm table setup). The basic measurement time
interval for: voltage, current, active, reactive and apparent power, harmonics and
unbalance alarms is a 10-cycle time interval. Flicker alarms are evaluated according to
the flicker algorithm (Pst
1min
>1min, Pst > 10min, Plt > 10min).
