Schweitzer Engineering Laboratories SEL-311B, Instruction Manual

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Date Code 20011205 Setting SEL
OGIC
Control Equations G-5
SEL-311B Instruction Manual
With a 52b contact connected, if the circuit breaker is open, the 52b contact is closed and input
IN101 is energized [IN101 = 1 (logical 1)]:
52A = !IN101 = NOT(IN101) = NOT(1) = 0
Thus, the SEL
OGIC
control equation circuit breaker status setting 52A sees an open circuit
breaker.
Example of NOT Operator ! Applied to Multiple Elements (Within Parentheses)
The SEL
OGIC
control equation trip unlatch setting is set as follows:
ULTR = !(50L + 51G)
Refer also to Trip Logic in Section 5: Trip and Target Logic .
In this factory setting example, the unlatch condition comes true only when both the 50L (low-set
overcurrent element pickup indication) and 51G (residual ground time-overcurrent element
pickup indication) Relay Word bits deassert:
ULTR = !(50L + 51G) = NOT(50L + 51G)
As stated previously, the logic within the parentheses is performed first. In this example, the
states of Relay Word bits 50L and 51G are ORed together. Then the NOT operator is applied to
the logic resultant from the parentheses.
If either one of 50L or 51G is still asserted [e.g., 51G = 1 (logical 1)], the unlatch condition is not
true:
ULTR = NOT(50L + 51G) = NOT(0 + 1) = NOT(1) = 0
If both 50L and 51G are deasserted [i.e., 50L = 0 and 51G = 0 (logical 0)], the unlatch condition
is true:
ULTR = NOT(50L + 51G) = NOT(0 + 0) = NOT(0) = 1
and the trip condition can unlatch, subject to other conditions in the trip logic (see Figure 5.1).
SEL
OGIC
Control Equation Rising Edge Operator /
The rising edge operator / is applied to individual Relay Word bits only—not to groups of
elements within parentheses. In this example, the SEL
OGIC
control equation event report
generation setting uses rising edge operators:
ER = /51P + /51G + /OUT103