5 Theory and internal operation
84
The swell threshold is a percentage of nominal voltage defined in Voltage events setup
menu. The swell threshold can be set by the user according to the use. Instrument
permits swell evaluation:
•
on single-phase systems, a voltage swell begins when the U
Rms(1/2)
voltage rises
above the swell threshold, and ends when the U
Rms
voltage is equal to or bellow
the swell threshold plus the 2% of hysteresis voltage (see Figure 5.8),
•
on three-phase systems two different evaluation techniques can be used for
evaluation simultaneously:
o
A swell begins when the U
Rms(1/2)
voltage of one or more channels is
above the swell threshold and ends when the U
Rms(1/2)
voltage on all
measured channels is equal to or bellow the swell threshold plus the 2%
of hysteresis voltage.
o
A swell begins when the U
Rms(1/2)
voltage of one channel rises above the
swell threshold, and ends when the U
Rms(1/2)
voltage is equal to or bellow
the swell threshold plus the 2% of hysteresis voltage, on the same phase.
A voltage swell is characterized by a pair of data: maximum swell voltage magnitude,
and duration:
•
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:
