8.13
Date Code 20080213 Instruction Manual SEL-351A Relay
Breaker Monitor and Metering
Breaker Monitor
Determination of
Relay Initiated Trips
and Externally
Initiated Trips
See BRE Command (Breaker Monitor Data) on page 10.15. Note in the BRE
command response that the accumulated number of trips and accumulated
interrupted current are separated into two groups of data: that generated by
relay initiated trips (Rly Trips) and that generated by externally initiated trips
(Ext Trips). The categorization of this data is determined by the status of the
TRIP Relay Word bit when the SEL
OGIC control equation breaker monitor
initiation setting BKMON operates.
Refer to Figure 8.3 and accompanying explanation. If BKMON newly asserts
(logical 0 to logical 1 transition), the relay reads in the current values (Phases
A, B, and C). Now the decision has to be made: where is this current and trip
count information accumulated? Under relay initiated trips or externally
initiated trips?
To make this determination, the status of the TRIP Relay Word bit is checked
at the instant BKMON newly asserts (TRIP is the logic output of Figure 5.1).
If TRIP is asserted (TRIP = logical 1), the current and trip count information
is accumulated under relay initiated trips (Rly Trips). If TRIP is deasserted
(TRIP = logical 0), the current and trip count information is accumulated
under externally initiated trips (Ext Trips).
Regardless of whether the current and trip count information is accumulated
under relay initiated trips or externally initiated trips, this same information is
routed to the breaker maintenance curve for continued breaker wear
integration (see Figure 8.3–Figure 8.7).
Relay initiated trips (Rly Trips) are also referred to as internally initiated trips
(Int Trips) in the course of this manual; the terms are interchangeable.
Factory Default Setting Example
As discussed previously, the SELOGIC control equation breaker monitor
initiation factory default setting is:
BKMON = TRIP
Thus, any new assertion of BKMON will be deemed a relay trip, and the
current and trip count information is accumulated under relay initiated trips
(Rly Trips).
Additional Example
Refer to Figure 8.8. Output contact OUT101 is set to provide tripping:
OUT101 = TRIP
Note that optoisolated input IN106 monitors the trip bus. If the trip bus is
energized by output contact OUT101, an external control switch, or some other
external trip, then IN106 is asserted.
Courtesy of NationalSwitchgear.com
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