4.81
Date Code 20100129 Instruction Manual SEL-751A Relay
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)
Settings associated with latches, timers, counters, math variables, and output
contacts are listed below.
SELOGIC Enables
The following table shows the enable settings for latch bits (ELAT), SELOGIC
control equations (including timers) (ESV), Counters (ESC), and math
variable equations (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
contact state. The SEL-751A 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
contact will go back 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 4.43). 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 4.31 Enable Settings
Setting Prompt Setting Range Default Setting
SELOGIC Latches N, 1–32 ELAT := 4
SV/Timers N, 1–32 ESV := 5
SELOGIC Counters N, 1–32 ESC := N
Math Variables N, 1–32 EMV := N
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