Megger MPQSIM, Руководство пользователя

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ADDENDUM C - SAMPLE POWER QUALITY TRAINING
AVTMMPQSIM Rev 1 May 2017
47

Verify the current phases angles are correct. Each phase current should be
within 90
°
of its phase voltage. If it is not within 90
°
then the current clamp
may be backwards.
Once these parameters are verified, start the recording by pressing the record button
on the MPQ Analyzer.
7. Create a Sag/Dip
a. Allow the unit to record for approximately 15 seconds (minimum).
b. Start a SAG / DIP on one of the voltage phases by setting the voltage selector to
85%.
c. Wait about 1 second.
d. Stop the SAG / DIP by setting the voltage selector back to 100%. Note the record
screen now will register a sag.
Facility operations can be affected by both long and short duration dips (sags).
Momentary voltage dips (sags) lasting less than 100 ms are often sufficient to cause
disruptions to equipment and operations. Momentary or short duration dips (sags)
can occur more frequently. Dips (sags) can be generated from either the load side of
the source side. Large loads turning on this can create high inrush currents that
create momentary dips (sags) on the voltage. Dips (sags) can also result from faults on
distribution circuits and transmission circuits.
Short duration dips (sags) are defined as a decrease in rms voltage between 0.1 pu and
0.9 pu for durations from 0.5 cycles to 1 min. Under-voltages with durations
exceeding 1 minute are considered to be long term duration events.
A dip (sag) event can either be a single phase event or a poly-phase phase event.
A dip (sag) is initiated when the ½ cycle RMS voltage of a single phase falls below the
dip (sag) threshold. The event ends when all phases are within above the dip (sag)
threshold plus any hysteresis programmed by the user.
The recommended thresholds for dip (sag) detection is 0.9pu the RMS value
aggregated every 1/2 cycle.
For example:
A 230V system the dip (sag) limit would be 228V.
A 120V system the dip (sag) limit would be 108V.