Schweitzer Engineering SEL-351P, Quick Start Manual

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8-8 Breaker/Recloser Monitor, Battery System Monitor, Date Code 990430
Metering, and Load Profile Functions
SEL-351P Manual Técnico
In Figure SECTION 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
®
Control Equation Breaker Monitor Initiation Setting BKMON
The SEL
OGIC
Control Equation breaker monitor initiation setting BKMON determines when the
breaker/recloser monitor reads in current values (Phases A, B, and C) for the breaker
maintenance curve (see Figure SECTION 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
OGIC
Control Equation breaker monitor initiation setting is
set:
BKMON = WBTR + WBTRT + \52A (WBTR and WBTRT are the trip logic outputs
of Figure 7.29)
Refer to Figure SECTION 8: .3. When BKMON asserts (e.g., Relay Word bit WBTR 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 SECTION 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 SECTION 8: .3: Operation of SEL
OGIC
Control Equation Breaker Monitor
Initiation Setting
See following subsection Determination of Control Initiated Trips and Externally Initiated
Trips for more information on the other part of the factory setting (. . . + WBTRT + \52A).