Sel 411L - Page 771

P.12.11
Date Code 20151029 Protection Manual SEL-411L Relay
Bay Control
Disconnect Logic
Word bit asserted, Relay Word bit 89CCMm asserts for one-quarter cycle
when the ENT pushbutton is pressed and
CLOSE DISCONNECT is highlighted in
the Control Screen.
Close, Open, and
Undetermined State
Indications
This subsection discusses the way the close and open immobility timers work
in conjunction with the disconnect alarm timer to provide disconnect control
and alarm indications. When the disconnect switch main contact is stationary
(closed or open) the state of the disconnect switch is easily determined.
If the disconnect switch main contact is open:
➤ normally closed b auxiliary contact (89BMm asserted) is closed
➤ normally open a auxiliary contact (89AMm deasserted) is open
If the disconnect switch main contact is closed:
➤ normally closed b auxiliary contact (89BMm deasserted) is
open
➤ normally open a auxiliary contact (89AMm asserted) is closed
If an operation of the disconnect switch is in progress, the state of the
disconnect switch main contact is undetermined:
➤ normally closed b auxiliary contact (89BMm deasserted) is
open
➤ normally open a auxiliary contact (89AMm deasserted) is open
Any undetermined state of the disconnect switch main contact should be
monitored. The relay can be configured to wait for the disconnect switch
operation to complete and issue an alarm if the disconnect switch remains in
the undetermined state longer than the 89ALPm time. Figure 12.6 illustrates
how the states of the auxiliary contacts change for an open-to-close operation
in progress and how the 89CSTm, 89CITm, and 89ALPm timers are
configured to manage the undetermined time. The close-to-open scenario
would be similar.
With the disconnect switch in the open state, the normally closed b auxiliary
contact is closed (89BMm asserted) and the normally open a auxiliary contact
is open (89AMm deasserted). The 89CSTm seal-in timer starts timing when a
disconnect switch CLOSE command is issued. The output of the 89CSTm
seal-in timer keeps the close signal asserted for the duration of the expected
disconnect switch operate time. Set the seal-in timer 10–15 percent longer
than the expected disconnect operate time to allow for slow disconnect
operation times caused by cold temperatures or low battery voltages.