U.5.42
SEL-421 Relay User’s Guide Date Code 20090715
Front-Panel Operations
Front-Panel Operator Control Pushbuttons
The SEL-421 has two types of outputs for each of the front-panel pushbuttons.
Relay Word bits represent the pushbutton presses. One set of Relay Word bits
follows the pushbutton and another set pulses for one processing interval
when the button is pressed. Relay Word bits PB1 through PB12 are the
“follow” outputs of operator control pushbuttons. Relay Word bits PB1_PUL
through PB12PUL are the pulsed outputs.
Annunciator LEDs for each operator control pushbutton are PB1_LED
through PB12LED. The factory defaults programmed for these LEDs are
protection latches (PLT01, for example), settings groups, Relay Word bits
(NOT SG1), and the status of the circuit breaker auxiliary contacts (52AA1).
The asserted and deasserted colors for the LED are determined with settings
PBnCOL. Options include red, green, amber, or off.
You can change the LED indications to fit your specific control and
operational requirements. This programmability allows great flexibility and
provides operator confidence and safety, especially in indicating the status of
functions that are controlled both locally and remotely.
Courtesy of NationalSwitchgear.com
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