Schweitzer Engineering SEL-351P, Quick Start Manual

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Date Code 990430 Setting SEL
OGIC
®
Control Equations G-7
SEL-351P Manual Técnico
on the same event report (generated by 51G1 asserting first). The assertion of OUT103 for a
breaker failure condition is some appreciable time later and will generate another event report, if
the first event report capture has ended when OUT103 asserts.
If the rising edge operators / were not applied and setting ER was:
ER = 51P1 + 51G1 + OUT103
the ER setting would not see the assertion of OUT103, because 51G1 and 51P1 would continue
to be asserted at logical 1, as shown in Figure APPENDIX G: .1.
SEL
OGIC
Control Equation Falling Edge Operator \
The falling edge operator \ is applied to individual Relay Word bits only – not to groups of
elements within parentheses. The falling edge operator \ operates similarly to the rising edge
operator, but looks for Relay Word bit deassertion (element going from logical 1 to logical 0).
The falling edge operator \ in front of a Relay Word bit sees this logical 1 to logical 0 transition
as a “falling edge” and asserts to logical 1 for one processing interval.
For example, suppose the SEL
OGIC
Control Equation event report generation setting is set with
the detection of the falling edge of an underfrequency element:
ER = ... + \81D1T
When frequency goes above the corresponding pickup level 81D1P, Relay Word bit 81D1T
deasserts and an event report is generated (if the relay is not already generating a report that
encompasses the new transition). This allows a recovery from an underfrequency condition to be
observed. See Figure 3.30 and Table 3.11 in
Section 3: Overcurrent, Voltage, Synchronism
Check, and Frequency Elements . Figure APPENDIX G: .2 demonstrates the action of the
falling edge operator \ on the underfrequency element in setting ER.
Figure APPENDIX G: .2: Result of Falling Edge Operator on a
Deasserting Underfrequency Element
SEL
OGIC
Control Equation Operation Example – Tripping
If tripping does not involve communications-assisted or switch-onto-fault trip logic, the SEL
OGIC
Control Equation trip setting TR is the only trip setting needed. Refer to
Trip Logic
in
Section 5: Trip and Target Logic .
Note that Figure 5.1 in Section 5: Trip and Target Logic appears quite complex. But since
tripping does not involve communications-assisted or switch-onto-fault trip logic in this example,
respective SEL
OGIC
Control Equation trip settings TRCOMM and TRSOTF are not used. The