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1 PRODUCT DESCRIPTION
After a settings change is made in the active settings group, the LPS-O automatically returns to its normal pro-
tection-on mode following:
•
Storage of the new setting values in nonvolatile memory.
•
A Trip Bus Check to determine that the changed settings have not caused any of the trip functions to oper-
ate for system conditions (that is, current and voltage at the relay) at that instant.
A Trip Bus Check also occurs before a newly selected settings group is allowed to become the active settings
group. If Trip Bus Check finds a picked-up trip function, protection is turned off and a critical alarm is issued.
This check provides a degree of confidence in the new settings, but it does not guarantee that one or more trip
functions might not operate as system conditions change. For example, a subsequent increase in load current
might cause the Zone 3 phase-distance function to operate, even though it did not operate at the instant the
Trip Bus Check was made.
The DC battery voltage across each of the open trip contacts (or SCRs) may be continuously monitored to
determine if the associated trip circuit is intact. If the monitored DC voltage drops to zero, then the trip circuit
has failed to open or the breaker 52/a contact (which is normally wired in series with the trip coil) has opened.
This function is intended to replace the red light indicator typically used for trip-circuit monitoring, and it can be
selectively disabled for each breaker.
There are four trip contacts (or SCRs) in the LPS-O. The voltage across each contact (or SCR) is monitored
separately. Any combination of trip circuits may be monitored by General Setting 107: NUM_MON.
Operation of the Trip Circuit Monitor causes a noncritical alarm event. If one or more poles of the breaker are
opened in some manner other than by a trip issued by the LPS-O, then the 52/a contact normally wired in
series with the trip coil opens and drops the voltage across the open contact to zero. To avoid a noncritical
alarm for this condition, closure of the associated 52/b contact disables the Trip Circuit Monitor function for the
involved pole.
Two separate alarms are provided. The output relays associated with these alarms are not user programma-
ble. Both of these alarms have form C contacts and are energized under normal conditions.
•
The critical alarm de-energizes when the relay self-test logic detects a problem that warrants taking the
relay system out of service.
•
The power supply alarm de-energizes when the power supply fails or is turned off.
A user programmable non-critical alarm is also provided. Operation of the non-critical alarm will cause an
event to be logged and may be programmed to a user-assigned output contact. The non-critical alarm is de-
energized in normal conditions. The default inputs to the non-critical alarm include the following conditions:
1. Trip Circuit Alarm
2. Zone Flags On Alarm
3. Overcurrent Alarm
4. Unbalance Current Alarm Detector
Additional inputs, such as Line Overload alarm, may be added with Xpression Builder.
GE Power Management
LPS-O Line Protection System
1.5 OTHER FEATURES
1.5.11 TRIP BUS CHECK
1.5.12 TRIP CIRCUIT MONITOR
1.5.13 ALARMS
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