Latch Control Switch Application Ideas; Reclosing Relay Enable/Disable Setting Example - Schweitzer Engineering Laboratories SEL-351 Instruction Manual

These latch control switches each have the following SEL
SETn
RSTn
If setting SETn asserts to logical 1, latch bit LTn asserts to logical 1. If setting RSTn asserts to
logical 1, latch bit LTn deasserts to logical 0. If both settings SETn and RSTn assert to logical 1,
setting RSTn has priority and latch bit LTn deasserts to logical 0.

Latch Control Switch Application Ideas

Latch control switches can be used for such applications as:
•
Reclosing relay enable/disable
•
Ground relay enable/disable
•
Sequence coordination enable/disable
Latch control switches can be applied to almost any control scheme. The following is an example
of using a latch control switch to enable/disable the reclosing relay in the SEL-351 Relay.

Reclosing Relay Enable/Disable Setting Example

Use a latch control switch to enable/disable the reclosing relay in the SEL-351 Relay. In this
example, a SCADA contact is connected to optoisolated input IN4. Each pulse of the SCADA
contact changes the state of the reclosing relay. The SCADA contact is not maintained, just pulsed
to enable/disable the reclosing relay.
Figure 7.14: SCADA Contact Pulses Input IN4 to Enable/Disable Reclosing Relay (Model
If the reclosing relay is enabled and the SCADA contact is pulsed, the reclosing relay is then
disabled. If the SCADA contact is pulsed again, the reclosing relay is enabled again. The control
operates in a cyclic manner:
pulse to enable ... pulse to disable ... pulse to enable ... pulse to disable ...
This reclosing relay logic is implemented in the following SEL
displayed in Figure 7.15.
7-14
Courtesy of NationalSwitchgear.com
(set latch bit LTn to logical 1)
(reset latch bit LTn to logical 0)
0351xT Example)
Inputs, Outputs, Timers, and Other Control Logic
SEL-351 Instruction Manual
Control Equation settings:
OGIC
Control Equation settings and
OGIC
Date Code 20001006