H.6
SEL-311C Relay Instruction Manual Date Code 20060320
Setting SELOGIC Control Equations
SEL
OGIC Control Equations
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).
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. In this example, the SEL
OGIC
control equation event report generation setting uses rising edge operators:
ER = /51P + /51G + /OUT103
The Relay Word bits in this example are:
51P Maximum phase current above pickup setting 51PP for phase time-
overcurrent element 51PT (see Figure 3.24)
51G Maximum residual ground current above pickup setting 51GP for
residual ground time-overcurrent element 51GT (see Figure 3.25)
OUT103 Output contact OUT103 is set as a breaker failure trip output (see
Output Contacts on page 7.32)
When setting ER sees a logical 0 to logical 1 transition, it generates an event
report (if the relay is not already generating a report that encompasses the new
transition). The rising edge operators in the above factory-setting example
allow setting ER to see each transition individually.
Suppose a ground fault occurs and a breaker failure condition finally results.
Figure H.1 demonstrates the action of the rising edge operator / on the
individual elements in setting ER.
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