Date Code 20001006 Setting SELOGIC
®
Control Equations G-5
SEL-351 Instruction Manual
With a 52b contact connected, if the circuit breaker is open, the 52b contact is closed and input
IN1 is energized [IN1 = 1 (logical 1)]:
52A = !IN1 = NOT(IN1) = NOT(1) = 0
Thus, the SELOGIC Control Equation circuit breaker status setting 52A sees an open circuit
breaker.
Example of NOT Operator ! Applied to Multiple Elements (Within Parentheses)
The SELOGIC Control Equation trip unlatch setting is set as follows:
ULTR = !(51P + 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 51P (phase
time-overcurrent element pickup indication) and 51G (residual ground time-overcurrent element
pickup indication) Relay Word bits deassert:
ULTR = !(51P + 51G) = NOT(51P + 51G)
As stated previously, the logic within the parentheses is performed first. In this example, the states
of Relay Word bits 51P and 51G are ORed together. Then the NOT operator is applied to the
logic resultant from the parentheses.
If either one of 51P or 51G is still asserted [e.g., 51G = 1 (logical 1)], the unlatch condition is not
true:
ULTR = NOT(51P + 51G) = NOT(0 + 1) = NOT(1) = 0
If both 51P and 51G are deasserted [i.e., 51P = 0 and 51G = 0 (logical 0)], the unlatch condition is
true:
ULTR = NOT(51P + 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).
SELOGIC Control Equation Rising Edge Operator /
The rising edge operator / is applied to individual Relay Word bits only – not to groups of elements
within parentheses. For example, the SELOGIC Control Equation event report generation setting
uses rising edge operators:
ER = /51P + /51G + /OUT3
Courtesy of NationalSwitchgear.com
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