Schweitzer Engineering Laboratories SEL-421-4 - Page 1180

13.14
SEL-400 Series Relays Instruction Manual Date Code 20171006
SELOGIC Control Equation Programming
SEL
OGIC Control Equation Elements
Example 13.6 Protection Latch Bits
This example studies the factory settings for the HOT LINE TAG operator
control logic in the SEL-451. Protection Latch Bit 4 (PLT04) is used as a
close enable signal, which is deasserted during Hot Line Tag conditions.
When the HOT LINE TAG operator control is pressed, Relay Word bit
PB5_PUL pulses for one processing interval, and one of two actions will
occur, depending on the previous state of PLT04:
➤ If PLT04 was previously asserted, the PB5_PUL is ANDed with
PLT04 in the PLT04R SEL
OGIC equation, causing PLT04 to
deassert. In this state, closing is blocked.
➤ If PLT04 was previously deasserted, the PB5_PUL is ANDed
with NOT PLT04 in the PLT04S SEL
OGIC equation, causing
PLT04 to assert. In this state, closing is permitted.
The settings below are duplicated in the Protection SEL
OGIC control equation
freeform programming areas corresponding to each of six setting groups:
# Store HOT LINE TAG state in PLT04, controlled by front panel pushbutton
#
PLT04S := PB5_PUL AND NOT PLT04
PLT04R := PB5_PUL AND PLT04 # HOT LINE TAG (WHEN PLT04
DEASSERTED)
#
# PLT04 defeats the RECLOSE ENABLED operator control function
PLT02R := PB2_PUL AND PLT02 OR NOT PLT04 # HOT LINE TAG
DISABLES RECLOSE
In the factory settings for PLT04S and PLT04R, rising edge operators are not
required because Relay Word bit PB5_PUL only asserts for one processing
interval. If the application required control input IN103 to set or clear the
Hot Line Tag function in addition to the operator control pushbutton, the set-
tings would look like this:
PLT04S := (PB5_PUL OR R_TRIG IN103) AND NOT PLT04
PLT04R := (PB5_PUL OR R_TRIG IN103) AND PLT04 # HOT LINE
TAG (WHEN PLT04 DEASSERTED)
If the R_TRIG operators were not present, Protection Latch Bit 4 (PLT04)
would oscillate whenever IN103 was asserted, and the final state after IN103
deasserts would be indeterminate. To prevent contact bounce sensed by Con-
trol Input IN103 from triggering multiple rising edges, make appropriate
debounce time settings.
Protection Latch Bit 4 (PLT04) appears in the factory settings for several
SEL
OGIC control equations in the SEL-451:
➤ In the Protection SELOGIC control equation freeform programming
area, PLT04 defeats the RECLOSE ENABLED operator control
function
PLT02R := PB2_PUL AND PLT02 OR NOT PLT04 # HOT
LINE TAG DISABLES RECLOSE
➤ In the front-panel settings, PB5_LED follows the inverted state
of PLT04:
PB5_LED := NOT PLT04 #HOT LINE TAG