4.158
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Logic Settings (SET L Command)
Time = 15 Minutes. The three five-minute intervals in the sliding time-window
at “Time = 15 minutes” each integrate into the following 5-minute totals:
Rolling demand meter response at “Time = 15 minutes” = 3.0/3 = 1.0 per unit.
Logic Settings (SET L Command)
The following discussion lists the settings associated with latches, timers,
counters, math variables, and output contacts.
SELOGIC Enables
Table 4.58 shows the enable settings for latch bits (ELAT), SELOGIC control
equations (including timers) (ESV), Counters (ESC), and math variable equa-
tions (EMV). This helps limit the number of settings that you need to make.
For example, if you need six timers, only enable six timers.
Latch Bits
Latch control switches (latch bits are the outputs of these switches) replace
traditional latching devices. Traditional latching devices maintain output con-
tact state. The SEL-751 latch control switch also retains state even when
power to the device is lost. If the latch control switch is set to a programmable
output contact and power to the device is lost, the state of the latch control
switch is stored in nonvolatile memory, but the device de-energizes the output
contact. When power to the device is restored, the programmable output con-
tact returns to the state of the latch control switch after device initialization.
Traditional latching device output contact states are changed by pulsing the
latching device inputs (see Figure 4.93). Pulse the set input to close (set) the
latching device output contact. Pulse the reset input to open (reset) the latching
device output contact. The external contacts wired to the latching device inputs are
often from remote control equipment (e.g., SCADA, RTU).
Five-Minute Totals Corresponding Five-Minute Interval
1.0 per unit 0 to 5 minutes
1.0 per unit 5 to 10 minutes
1.0 per unit 10 to 15 minutes
3.0 per unit
Table 4.58 Enable Settings
Setting Prompt Setting Range Default Setting
SELOGIC Latches N, 1–32 ELAT := 4
SV/Timers N, 1–32 ESV := 5
SEL
OGIC Counters N, 1–32 ESC := N
Math Variables N, 1–32 EMV := N
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