R.3.16
SEL-421 Relay Reference Manual Date Code 20111215
SELOGIC Control Equation Programming
SELOGIC Control Equation Elements
protection latch value remains unchanged for a change in the active protection
settings group, you can enter different Set and Reset programming for each
protection settings group.
There are Set and Reset settings for each latch bit available in each group. For
example, PLT01R and PLT01S are available in all six free-form settings
groups and all control the same Latch Bit, PLT01. This structure allows you to
either program each latch to operate in the same way for each group or behave
differently based on the active protection settings group. For example, you
could program the protection latch to set on IN107 when Protection Settings
Group 1 is active and program the latch to set on IN106 when Protection
Settings Group 2 is active. If you do not enter a setting for the Reset and Set in
a protection settings group, the latch bit will remain unchanged when that
protection settings group is active. Example 3.6 illustrates protection latch bit
usage.
EXAMPLE 3.6 Protection Latch Bits
In this example, Remote Bit 2 (RB02) is a blocking command for
remote control to the relay. A latch bit stores the incoming command
and preserves the state associated with the command through a
power cycle. Remote Bit 1 sends the operator-initiated circuit breaker
open/close command. Because the protection design uses protection
settings groups 1 through 3, the settings shown below are duplicated
in protection SEL
OGIC control equation free-form programming areas
associated with protection settings groups 1 through 3.
#
# Store incoming remote command block in Protection Latch Bit 2
#
PLT01R := RB02 AND PLT01 # Reset latch if RB02 off and latch set
PLT01S := RB02 AND NOT PLT01 # Set latch if RB02 on and latch not set
#
# Use PSV30, PSV31 to calculate open and close conditions
#
PSV30 := RB01 AND NOT PLT01 # Open if RB01 and not blocked
PSV32 := R_TRIG PSV30 # One processing interval Open command
PSV31 := NOT RB01 AND NOT PLT01 # Close if RB01 off and not blocked
PSV33 := R_TRIG PSV31 # One processing interval Close command
In this example, PSV32 and PSV33 are used in the trip and close
equations. PSV34 will be set to 1 for an open command and reset to 0
for a trip command. The TRIP and CLOSE equations are shown below:
BK1MTR := PSV32 # Remote manual trip RB02 supervised with RB01 enable
BK1MCL := PSV33 # Remote manual close RB02 supervised with RB01
enable
Evaluation of the latch bit value occurs at the end of the protection SELOGIC
control equation execution cycle. The values evaluated for Reset (PLTnnR)
and Set (PLTnnS) during SEL
OGIC control equation execution remain
unchanged until after the evaluation of all SEL
OGIC control equations, when
the relay evaluates the latch bit value (PLTnn). For example, if you have
multiple SEL
OGIC control equations for set, the last equation in the protection
free-form area dominates, and the relay uses this equation to evaluate the
latch.
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