Operation Of Sel Ogic Control Equation Breaker Monitor Initiation Setting Bkmon - Schweitzer Engineering Laboratories SEL-351R Instruction Manual

In Figure 8.2, note that the breaker maintenance curve levels off horizontally below set point
KASP1, COSP1. This is the close/open operation limit of the circuit breaker (COSP1 = 10000),
regardless of interrupted current value.
Also, note that the breaker maintenance curve falls vertically above set point KASP3, COSP3.
This is the maximum interrupted current limit of the circuit breaker (KASP3 = 20.0 kA). If the
interrupted current is greater than setting KASP3, the interrupted current is accumulated as a
current value equal to setting KASP3.
Operation of SEL
OGIC
The SEL control equation breaker monitor initiation setting BKMON determines when the
OGIC
breaker/recloser monitor reads in current values (Phases A, B, and C) for the breaker
maintenance curve (see Figure 8.2) and the breaker monitor accumulated currents/trips [see BRE
Command (Breaker Monitor Data) in Section 10: Serial Port Communications and
Commands].
The BKMON setting looks for a rising edge (logical 0 to logical 1 transition) in its associated
logic equation as the trigger to read in current values. The acquired current values are then
applied to the breaker maintenance curve and the breaker monitor accumulated currents/trips
(see references in previous paragraph).
In the factory default settings, the SEL
set:
BKMON = TRIP
Refer to Figure 8.3. When BKMON asserts (Relay Word bit TRIP goes from logical 0 to
logical 1), the breaker monitor reads in the current values and applies them to the breaker
monitor maintenance curve and the breaker monitor accumulated currents/trips.
As detailed in Figure 8.3, the breaker/recloser monitor actually reads in the current values 1.5
cycles after BKMON asserts. This delay ensures that the current has reached its peak value,
especially for an instantaneous trip operation. The instantaneous element trips when the fault
current reaches its pickup setting level. The fault current may still be "climbing" to its full value
and then will level off. The 1.5-cycle delay allows time for the fault current to level off before
the current values are recorded by the contact wear monitor.
Figure 8.3: Operation of SEL
See Figure 8.8 and accompanying text for more information on setting BKMON. The operation
of the breaker monitor maintenance curve, when new current values are read in, is explained in
the following example.
Date Code 20020215
Control Equation Breaker Monitor Initiation Setting BKMON
OGIC
(TRIP is the logic output of Figure 5.1)
Control Equation Breaker Monitor Initiation Setting
OGIC
Breaker/Recloser Monitor, Battery System Monitor,
Metering, and Load Profile Functions
SEL-351R Instruction Manual
control equation breaker monitor initiation setting is
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