Megger MPQSIM, Руководство пользователя

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M
AVTMMPQSIM Rev 1 May 2017
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10. Create a THD Event
a. Allow the unit to record for approximately 15 seconds (minimum).
b. Turn ON one of the voltage and current harmonic switches.
c. Let the unit record for about 1 minutes.
d. Turn OFF the voltage and current harmonic switches.
e. Let the unit record for about another 15 seconds then stop the recording.
The MPQ PQ Analyzer will record harmonics as a trended value. It will also record
Total Harmonic Distortion (THD) as a PQ event.
A THD event is initiated when the THD value (aggregated over a 200msec period) of
a single channel rises above the THD threshold. The event ends when the THD
value (aggregated over a 200msec period) of a single channel drops below the THD
threshold.
Note THD value for current channels can be misleading. THD is represented as a
percentage of the fundamental value. The voltage fundamental value is a constant
value. The current fundamental value can fluctuate based on the changing load
impedance. This make THD evaluation on current channel difficult. IEEE 519
recommends using Total Demand Distortion (TDD) to analyze current distortion.
TDD references the harmonic content of the current channels to the maximum
average current drawn within the test interval. This can be analyzed in the PC
software provided the unit is programmed to capture periodic waveforms.
11. Create a Phase Event (Loss of phase)
a. Allow the unit to record for approximately 15 seconds (minimum).
b. Start a Phase Event by setting one of the Voltage Phase switches to +11
°
.
c. Wait about 1 second.
d. Stop the Phase Event by setting the voltage phase switch selector back to
nominal.
Note the record screen now will register a Phase Event.
The phase angle shift (jump) manifests itself as a shift in zero crossing of the
instantaneous voltage. Change in the phase angle of the voltage can affect power-
electronics converter and relays that use phase angle information for their firing
instant. The inconsistent nature of renewable energy such as wind and solar can lead
to inverters turning on and off leading to phase shift phenomenon. These can also be
caused by system faults.
The phase angle is referenced from Phase A voltage. The phase angle of the Phase B
Voltage and Phase C voltage are measured relative to Phase A voltage. If the Phase B
or C voltage deviated by more than the programmed amount from nominal then a
phase shift event occurs.