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PA-9 Series
Application Guide
WAVY CRT
Wavy CRT: A wavy CRT or a visual flicker in a CRT can be due
to harmonics on the AC line. Transients can also cause the CRT to
flicker as well.
Common causes of harmonics include electronic loads and
SCR/Rectifier loads.
Common Causes of transients include lightning, load switching,
capacitor switching as well as loose wiring.
Other Common Causes include:
Buildings being located too close to high voltage lines. In these
cases the customer options include adding shielding or
switching over to LCD screens.
EMF interference from PC screens being located too close to
an electrical service entrance coming into a building. This is
especially true in overhead services.
Old houses with knob & tub wiring as the fields form the
wiring method do not cancel.
Also if one phase is lost in a three phase service this can cause
EMF interference due to lack of field cancellation.
Example of a third harmonic
PA-9 Configuration
Feature Status Notes
Enable Power Calculations Enable (Select correct configuration)
Enable RMS Recording Enable
MIN, RMS and MAX MIN, RMS and MAX
Clock Hour Orientation Enabled
Enable Flicker Recording Disabled
Hysteresis 2%
Sags Enabled
This configuration is designed to
focus on Harmonic detection, as
well as sub-cycle events. Note
that the waveform capture is set
to THD. The time interval
between waveform captures
should be set to the same time
interval of the storage interval.
PA-9
Application Guide
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ISO STATEMENT
Registered to ISO 9001:1994 Reg no. Q 09250
Registered to ISO 14001 Reg no. EMS 61597
PA9_13_AG_En_V02
www.megger.com
Megger is a registered trademark
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Feature Status Notes
Sag Limit See Below
Swells Enabled
Swell Limit See Below
Sub-cycle Enabled
Sub-Cycle Limit See Below
THD Limit Disabled
THD Limit NA
Enable Waveform Capture Enabled
Waveform Trigger THD
Pre-Triggers NA
Post Triggers 5
Waveform Limit Disabled
Expected Number of Events NA
Memory Mode Stop When Full
Default Frequency 50 or 60Hz as Required
Enable Frequency Recording Enabled
MIN, AVG, MAX AVG
The length of this interval should
be determined by how long the
unit is intended to record.
The unit will now capture
waveforms every storage interval
which will allow the software to
perform THD and Harmonic
trending. This is the data required
to find steady state harmonic
problems.
NOTE: THD event limit is
disabled. Since the intent is to
capture steady state harmonics
the event THD is not required.
IEEE Recommendations: For a 120V / 60Hz Load
per IEEE1159.
Sag Limit = 108V (10% of Nominal)
Swell Limit = 126V (5% of Nominal)
Sub-cycle = 200V (Approx 2 times Phase to Neutral)
European Recommendations: For a 230V / 50Hz Load
per EN50160.
Sag Limit = 207V (10% of Nominal)
Swell Limit = 253V (10% of Nominal)
Sub-cycle = None Provided
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