Allen-Bradley 1404-M4, User Manual

Page: 165 / 356

Publication 1404-UM001D-EN-E - October 2004
Advanced Features 8-15
If the nominal system voltage setting is changed, the high and low
limits for setpoint #19 and #20 are automatically adjusted to 90% and
110% of the nominal system voltage.
To effectively use sag and/or swell detection:
1. Set ‘RMS result averaging’ to 0 (no averaging) for the quickest
setpoint response to changes in input voltage.
2. Alter setpoint configuration if necessary to adjust the sensitivity
to sags and/or swells.
3. If using the setpoint to trigger an oscillograph capture, make
sure there is at least one capture location that is clear and ready
to accept a new capture.
4. Periodically check the event log or capture ready status for an
indication that a sag or swell has occurred.
5. Read the event log to get the timestamp, duration of the
disturbance, the worst case magnitude, and the identifier of the
capture.
6. Find the capture that has the same identifier as the one found in
the event log record by reading the first block from each capture
location. Read the entire capture from the Powermonitor 3000.
Depending on the duration of the disturbance, the capture may
contain additional information prior to and during the sag or
swell event.
The sag or swell duration reported in the event log has a tolerance of
± 2x the metering update rate. Refer to Metering Update Rate on
page 3-33 for more information. For sag and swell durations less than
500 milliseconds, examining the oscillograph data can result in a more
accurate determination of sag or swell duration.
References:
IEEE Std 1159-1995, “IEEE Recommended Practice for
Monitoring Electric Power Quality”, page 5,6,12.
The Institute of Electrical & Electronics Engineers Inc, 345 East
47
th
Street, New York, NY 10017-2394, ISBN 1-55937-549-3
TIP
Refer to Chapter 5, Setpoint Programming and
Operation for more information on setpoints.
Allen-Bradley HMIs