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4.8 Power Quality
The Digitrip 1150V in a Type VCP-T Breaker can measure
a variety of parameters relating to today's modern Power
System. This data can be viewed locally or via a computer
remotely in which case the data can be logged.
4.8.1 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. Max PF and Min 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
27th harmonic and Crest Factor are available via a wave-
form capture trigger. This waveform capture trigger can be
done locally by selecting HARMONIC in the Main Menu or
by exceeding a THD alarm threshold programmed by the
user. See section 4.8.2.
4.8.2 Alarms
Alarming on low power factor can be accomplished by
enabling this function in the ALARM programming screen.
Any System Power Factor seen by the Digitrip 1150V less
than the level programmed will initiate an alarm message
on the twenty four character display as well as illuminating
the yellow LED and communicating to a host computer.
The powerfactor calculation is valid for currents less than
the Long Delay Pickup level. The Auxiliary Relay A can be
assigned to this Low PF Alarm.
The THD alarm feature is an alarm setting with a range of
10% to 30% THD that when exceeded will initiate wave-
form capture and also set the front panel alarm LED. The
THD alarm has a 1 minute update rate. The Auxiliary
Relay A can also be assigned to the THD alarm.
4.9 Waveform Capture Feature
The Digitrip 1150V can respond to a command from a
remote master to perform a waveform capture of phase
currents IA, IB and IC or waveform IG when employing the
source ground jumper. A total of fifty eight data points per
phase per cycle is captured and can be sent to a host
computer. From this data, parameters such as [THD],
individual harmonics content and waveform are fabricated.
There is a timer in the Digitrip unit that will limit the
acceptance of a "WAVEFORM CAPTURE" software
command to once per second. Three waveforms are held in
a first in, first out manner in the Digitrip's volatile memory.
4.9.1 Six Cycle Waveform Capture on Trip
On Long Time, Short Time, Instantaneous or Ground Fault
tripping events, the Digitrip 1150V will capture the curve
waveforms to a buffer. The buffer as a waveform can be
displayed on the master computer using the PowerNet
software screen (Ref. I.L.17384 for protocol and software
commands). The six cycle waveform capture will typically
contain one cycle of pre-interruption data and five cycles of
interruption and post-interruption data for analysis of the
power system.
NOTE: The phase loss, phase unbalance, voltage and
frequency trips, reverse power trips and alarm events do
not produce a waveform capture.
NOTE: PowerNet communications will require hardware
and software specified in the Cutler-Hammer PowerNet
Operations Manual.
4.9.2 One Cycle Waveform Capture
There are two methods of obtaining a one cycle waveform
capture from the Digitrip 1150V. One method is via the
PowerNet software to manually request a waveform
capture. The second way is to trigger a waveform capture
via an Alarm condition. This is accomplished by entering
the PROGRAM - ALARM screen. Enable the ALARM type
of interest as well as ALARM TO EventLOG. The one cycle
waveform capture of the currents IA, IB, IC can then be
displayed on the master computer for analysis. IG wave-
form is not displayed for residual ground application (See
Appendix D-16).
5.0 TEST PROCEDURES
5.1 General
DO NOT ATTEMPT TO INSTALL, TEST, OR PERFORM
MAINTENANCE ON EQUIPMENT WHILE IT IS ENER-
GIZED. DEATH OR SEVERE PERSONAL INJURY CAN
RESULT FROM CONTACT WITH ENERGIZED EQUIP-
MENT.
DE-ENERGIZE THE CIRCUIT AND DISCONNECT THE
CIRCUIT BREAKER BEFORE PERFORMING MAINTE-
NANCE OR TESTS.
I.L. 66A7535H02
WARNING
Effective 11/2003
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