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Alternate IEEE Sign Convention
This setting uses the direct mathematical convention where
P = VI. Where power is the complex product of volts times
current. The sign of PF is positive if the signs of Watts and
VARs are the same. A lagging PF is negative.
The reverse feed setpoint can be used to invert the phase
of the current when the breaker is wired in a back-feed
configuration. The effect of setting this setpoint to reverse
feed is to interchange quadrants 1& 3 and 2 & 4. For more
information refer to
Appendix E: Power and Power Factor
Sign Conventions
.
The phase angle between voltage and current is always the
phase of current relative to voltage. A phase angel (theta) of
+45 degrees implies the fundamental current leads the voltage
by 45 degrees. The terms “leading” and “lagging” current
are always with respect to the source of real power. If theta
e/- 90 degrees, the load is supplying power and the
current “leads” for phase angels 180 > theta > 270. Quadrants
1 & 3 are “leading” while quadrants 2 & 4 are “lagging”.
Power factor, THD and Crest Factor (CF)
The system power factor is a real-time measurement with
approximately a one second update rate. The tolerance is the
value ±0.02. Maximum PF and minimum PF values are historic
values that are held until reset.
Total harmonic distortion (THD) of each phase and neutral (if
valid) and corresponding per harmonic data up to the 31st
harmonic and crest factor are available via a waveform capture
trigger. This waveform capture trigger can be done locally
by selecting HARMONICS submenu from the MAIN menu.
The harmonic information displayed is historical from the last
waveform capture that was performed. A new capture can be
initiated in this submenu.
Auxiliary Relays
The programmable auxiliary relays in the trip unit consist
of Relay 1 and Relay 2. The relays can be independently
programmed to close for alarming OR tripping functions. More
than one function can be assigned to each relay.
Power factor and THD - Alarms
Alarming on low power factor can be accomplished by enabling
this function. Any system power factor seen by the Digitrip
1150 less than the level programmed will initiate an alarm
condition illuminating the LED and causing an event log. The
power factor calculation is valid for currents less than the Long
Delay Pickup level. The auxiliary Relays 1 or 2 can be also
assigned to the THD alarm.
The THD alarm feature is an alarm setting with a range of
10-30% THD that when exceeded will initiate a waveform
capture and also set the front panel Alarm LED. The THD alarm
has an associated time setting of 1 to 250 seconds.
27
EATON
www.eaton.com
Effective September 2013
Instructional Leaflet IL01301064E
Operating Manual for Series NRX
Digitrip Trip Units 1150 / 1150i