5.11
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Control
Remote Bits
connect switch operate time. Set the seal-in timer 10 to 15 percent longer than the
expected disconnect operate time, to allow for slow disconnect operation times
caused by cold temperatures or low battery voltages.
When the normally closed auxiliary contact (SELOGIC input 89BMm) deasserts,
the disconnect switch is in an undetermined state. No proper position indication
from either of the disconnect switch auxiliary contacts (89BMm or 89AMm) is
available. Once the auxiliary normally closed contact (SEL
OGIC input 89BMm)
deasserts, the 89ALPm timer starts timing. The 89ALPm timer monitors the
undetermined state of the disconnect switch. For the 89ALPm timer to initialize,
the disconnect switch has to move a minimum distance to open the normally
closed auxiliary contact (open-to-close operation). Set the 89ALPm timer longer
than the expected undetermined state time, but less than the 89CSTm seal-in
timer. If the normally open auxiliary contact fails to close within the undeter-
mined state time, the 89ALPm timer expires and an alarm condition is declared.
The Close Immobility Logic starts the Close Immobility Timer for an operation
where the disconnect switch does not move the minimum distance to open the
normally closed auxiliary contact (open-to-close operation). When the close
immobility timer expires, an alarm condition is declared and Relay Word bit
89ALm asserts. If the disconnect moves enough to open the normally closed aux-
iliary contact, the Close Immobility timer resets and no alarm condition is
declared (see Figure 5.4).
Remote Bits
Remote bits provide a means for sending remote control commands to relay
logic. As indicated in CONTROL nn on page 14.16, remote bits have three oper-
ating states: clear, set, and pulse. It is important to understand the differences
between the use of pulsed remote bits in automation and protection SEL
OGIC
Figure 5.6 Disconnect in Transition
Disconnect Close
Command Issued
Disconnect Main
Contact in Transition
Disconnect Close
Operation Completed
Normally Closed Form B
Contact (89BMm)
Normally Open Form A
Contact (89AMm)
Expected Disconnect Operate Time
89BMm Form B Contact
Closed
89BMm deasserts and
89ALPm begins timing
89AMm Form A
Contact Closed
89ALPm Alarm
Timer Duration
Undetermined State
89CSTm Seal-In Timer
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