Schweitzer Engineering SEL-351P - Latch Control Switch States Retained; Power Loss; Reset Latch Bits for Active Setting Group Change; Settings Change or Active Setting Group Change

7-16 Inputs, Outputs, Timers, and Other Control Logic Date Code 990215
SEL-351P Manual Técnico
SET1 = /RB1 * !LT1 [= (rising edge of remote bit RB1) AND NOT(LT1)]
RST1 = /RB1 * LT1 [= (rising edge of remote bit RB1) AND
LT1]
79DTL = !LT1 [= NOT(LT1); drive-to-lockout setting]
Pulse remote bit RB1 to enable reclosing, pulse remote bit RB1 to disable reclosing, etc. – much
like the operation of optoisolated input IN104 in the previous example. Remote bits (Relay
Word bits RB1 through RB8) are operated through the serial port. See
Figure SECTION 7: .9
and Section 10: Serial Port Communications and Commands for more information on remote
bits.
These are just a few control logic examples – many variations are possible.
Latch Control Switch States Retained
Power Loss
The states of the latch bits (LT1 through LT8) are retained if power to the relay is lost and then
restored. If a latch bit is asserted (e.g., LT2 = logical 1) when power is lost, it comes back
asserted (LT2 = logical 1) when power is restored. If a latch bit is deasserted (e.g., LT3 =
logical 0) when power is lost, it comes back deasserted (LT3 = logical 0) when power is restored.
This feature makes the latch bit feature behave the same as traditional latching relays. In a
traditional installation, if power is lost to the panel, the latching relay output contact position
remains unchanged.
Settings Change or Active Setting Group Change
If individual settings are changed (for the active setting group or one of the other setting groups)
or the active setting group is changed, the states of the latch bits (Relay Word bits LT1 through
LT8) are retained, much like in the preceding “Power Loss” explanation.
If individual settings are changed for a setting group other than the active setting group, there is
no interruption of the latch bits (the relay is not momentarily disabled).
If the individual settings change or active setting group change causes a change in SEL
OGIC
Control Equation settings SETn or RSTn (n = 1 through 8), the retained states of the latch bits
can be changed, subject to the newly enabled settings SETn or RSTn.
Reset Latch Bits for Active Setting Group Change
If desired, the latch bits can be reset to logical 0 right after a settings group change, using
SEL
OGIC Control Equation setting RSTn (n = 1 through 8). Relay Word bits SG1 through SG6
indicate the active setting Group 1 through 6, respectively (see
Table SECTION 7: .3).
For example, when setting Group 4 becomes the active setting group, latch bit LT2 should be
reset. Make the following SEL
OGIC Control Equation settings in setting Group 4:
SV7 = SG4
RST2 = !SV7T + ... [= NOT(SV7T) + ...]