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Alarms and Faults
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11.2.2 History Log
When a designated major alarm occurs, the History Status buffer is frozen, capturing 64 sequential frames
before and after the alarm condition. When the History Status buffer is frozen, a History Log is created.
Two History Logs are available to track major alarms. This log includes the triggering event plus the
surrounding events and the system voltages, currents, frequency, power, source selection and breaker
positions at the time of the event. The History Log displays the 64 sequential frames, in 4-millisecond
intervals, of the Present Status screens surrounding the event.
If you are viewing the log from the touch screen, the Mimic and the Event Display show the data that
was present as the alarm was triggered. The data is displayed as frames are played.
The History Log allows you to replay the events leading up to the alarm and the events right after the
alarm to see the status of the switch at that time and diagnose the cause of the alarm. The History
Log is triggered when certain events are tripped that have the Freeze option enabled.
You can run through the frames sequentially. The sequence of the events is identified by date, time
and frame number. The History Log frames are stored in a nonvolatile memory buffer that is continu-
ously overwritten until a designated fault condition occurs. When the fault occurs to trigger a freeze,
the History Log stores the next 23 frames, then freezes until it is reset. The History Log then keeps 40
frames before the fault, the frame where the fault occurred, plus the next 23 frames.
The History Log should not be reset until the fault condition that caused the buffer to freeze is
reviewed and investigated by a qualified service technician. After the alarm condition has been cor-
rected, the History Log can be cleared.
The History Log has the following fields:
• Replay Rate — indicates how long it takes for the replay to play. Use the UP and DOWN buttons
to set the time.
• Status — the status of the STS2/PDU at the point of the current frame in the replay. The History
log has three statuses: Frozen, Not Frozen and Retrieving Data, please stand by.
• Critical Event — The event which triggered this log to be written. The event is indicated in red on
the bar graph.
• Frame Number — the current frame in the replay. A negative number indicates the replay is at a
point before the triggering event occurred.
11.3 Alarm Notes
The I-PK on Source 1 and I-PK on Source 2 alarms inhibit automatic transfer due to an overload or
load fault. These alarms can be set for either auto or manual alarm reset.
In the auto reset mode, the alarm is reset as soon as the load current and source voltage return to are
inhibited until the conditions return to normal and the user manually presses the RESET button. In
either case, the cause of the Source 1 or Source 2 Ipeak overload should be investigated and resolved
(such as by reducing the overload condition or clearing the output fault) before returning the switch to
normal operation.
These events indicate a device failure. The device must be replaced and the system must be restarted
for the fault to clear. A shorted SCR automatically trips open a source input switch (CB1 or CB2) to pre-
vent transfers in the event of an SCR failure. The SCR failure must be investigated and repaired before
returning the switch to normal operation. Both source input switches must be opened (such as when
the unit is placed in maintenance bypass for servicing) before a shorted or open SCR alarm can be reset.
11.4 List of Messages
Table 12 lists available event messages, a definition of the event and the functions that are activated
with the event by default. The functions are indicated as follows:
D — The indicated event initiates the Auto-Dial sequence through the optional modem.
A — The indicated event activates the Audible alarm.
F — The indicated event triggers a Freeze of the History Log.
L — The indicated event Latches. A latched alarm remains displayed until the alarm condition
has cleared and the RESET button has been pressed.
E — By default, all faults and alarms are written to the Event Log. See 12.1.4 - Setting Event
Masks with the Terminal.
All of these functions, except Freeze, can be reconfigured to trigger for each event, using the Event Mask
option. See 11.1 - Event Mask. The Freeze function is hard-coded and cannot be changed for a event.