Time Synchronization - GE ALPS Instruction Manual

1.5 OTHER FEATURES 1 PRODUCT DESCRIPTION
1
Figure 1–9: SWITCH SELECTION OF ACTIVE SETTING GROUP

1.5.11 TIME SYNCHRONIZATION

The ALPS includes a clock that can run freely from the internal oscillator or be synchronized from an external signal. An
unmodulated IRIG-B signal connected to the IRIG-B terminals, located on terminal block "D" on the rear panel, may be
used to synchronize the clock. The clock in a given ALPS is synchronized to within ±1 ms of any other ALPS clock, if the
two relays are wired to the same synchronizing signal.
1.5.12 TRIP BUS CHECK
After a settings change is made in the active settings group, the ALPS automatically returns to its normal protection-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 operate 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.
1.5.13 TRIP CIRCUIT MONITOR
Within the ALPS relay system 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.
1-18 ALPS Advanced Line Protection System GE Power Management