Introduction
7
1.10
Logs
The SB Energy-Comm trip unit maintains three logs: a trip log in
nonvolatile memory to document up to five of the most recent
trips, an event log to document up to ten of the most recent
alarms, and a min/max log containing minimum and maximum
metered values.
1.10.1 Trip Log
All SB Energy-Comm trip unit models maintain a trip log in nonvol-
atile memory to store information for up to five of the most recent
device trips. Each log entry records the trip’s cause, its date and
time, and the measured quantities associated with the tripping
action. The trip log may be viewed and cleared through the trip
unit’s LCD menu or through communications.
1.10.2 Event Log
All SB Energy-Comm trip unit models provide an event log to
store the ten most recent alarms. Each entry includes a sequen-
tial event number (used by the ACCESS master), an alarm ID
indicating the alarm type, the start and stop time stamps, and up
to five parameters associated with the alarm.
The ten alarm functions are prioritized (that is, overcurrent alarm
is highest priority, total harmonic distortion alarm is lowest). This is
done to insure that only one alarm will be recorded in the event
log at a time. If two alarm functions become active simultaneously,
the higher priority alarm (Alarm #1) will be written to the event log.
The lower priority alarm (Alarm #2) will not be recorded until
Alarm #1 conditions have ended. If Alarm #2 conditions cease
before those associated with Alarm #1, Alarm #2 will not appear in
the event log.
Like the trip log, the event log may be viewed and cleared locally
using the trip unit’s keypad and LCD menu or through EIA-232 or
EIA-485 communications. However, because the event log
resides only in RAM, it is lost if control power is removed.
1.10.3 Min/Max Log
The SB Energy-Comm trip unit’s full-featured model also main-
tains a min/max log for metered quantities. This includes the mini-
mum and/or maximum values detected for currents, voltages,
leading and lagging power factors, instantaneous VA and VARs,
crest factors, frequency, kW and amp demand, as well as total
harmonic distortion. Like the trip log, the min/max log may be
viewed and cleared at the trip unit or through communications.
The min/max log resides only in RAM and is lost if control power is
removed. These logs are described in detail in
Chapter 10,
Logs.
1.11
Communications
1.11.1 ACCESS Communications
The EIA-485 communications port is located on the back of the
SB Energy-Comm trip unit. This port allows the trip unit to be con-
nected as a slave device in an ACCESS master/slave network.
Data is transmitted serially between the trip unit and a remote
ACCESS master (e.g., Power Monitor) using a shielded, twisted-
pair EIA-485 cable. The EIA-485 communications standard is
superior to EIA-232 for industrial applications, providing better
noise rejection and faster transmission rates over greater
distances.
With few exceptions, the device information available locally at the
trip unit is accessible to the ACCESS bus master (for example,
configuration parameters, function settings, and real-time data).
Although the ACCESS master may request information from the
trip unit at any time, it is prevented from making device changes
while an operator is using the trip unit’s keypad to locally view/
modify device information. In fact, a local operator at the keypad is
given priority over both EIA-485 and EIA-232 communications to
ensure against data access violations.
1.11.2 Serial Communications
The EIA-232 serial port on the face of the SB Energy-Comm trip
unit allows a PC or laptop running custom software to view and/or
modify device information in much the same way as the ACCESS
host. Settings can be easily downloaded to the trip unit, providing
a faster, more convenient means for device configuration than the
manual keypad method. EIA-232 communications can occur with,
and are independent of, EIA-485 ACCESS communications.
