P.12.5
Date Code 20151029 Protection Manual SEL-411L Relay
Bay Control
Disconnect Logic
89CCm, 89OCm
The 89CLOSE command or Fast Operate disconnect close message, pulses
Relay Word bit 89CCm for one-quarter cycle. The 89OPEN command or Fast
Operate disconnect open message, pulses Relay Word bit 89OCm for one-
quarter cycle. The LOCAL Relay Word bit must be deasserted for a
disconnect switch operation to be initiated by a Fast Operate message or
89CLOSE and 89OPEN commands.
Disconnect Seal-In Timer Settings
89CSTm, 89OSTm
89CSTm and 89OSTm settings are for defining the time required for the
disconnect switch to complete a close or open operation.
Disconnect Switch Close and Open Control Logic Output
89CLSm, 89OPENm
The 89CLSm and 89OPENm Relay Word bits are used in SELOGIC output
equations to perform close and open disconnect switch operations.
The output contacts in the relay are not designed to break the coil current in the disconnect motor.
An auxiliary contact with adequate current interrupting capacity must clear the coil current in the
disconnect motor before the output on the relay opens. Failure to observe this safeguard could
result in damage to the relay output contacts.
Disconnect Switch Close and Open Control Logic Processing
Figure 12.1 shows the disconnect switch close logic and Figure 12.2 shows
the disconnect switch open logic.
Some motor-operated disconnect switches have their own seal-in circuits to
seal the closing and opening signals in. Other motor-operated disconnect
switches, however, require external sealed-in circuits to maintain the closing
and opening signals for the duration of the disconnect operation.
With SEL
OGIC equations 89CRSm and 89ORSm set to the default settings
(include Relay Word bits 89CSIm and 89OSIm), the open and close signals
remain asserted for the time settings of the Close and Open Seal-In Timers,
89CSTm and 89OSTm.
If the 89CBLm SEL
OGIC control equation and the 89OPEm and the LOCAL
Relay Word bits are deasserted, then any of the close disconnect operate
methods (except operation from the front-panel one-line diagram) can assert
Relay Word bit 89CLSm, and initiate the Close Seal-In Timer, 89CSTm. Enter
Relay Word bit 89CLSm into a SEL
OGIC output equation to drive the motor of
the disconnect switch.
Set the Close Seal-In Timer, 89CSTm, long enough to keep Relay Word bit
89CLSm asserted long enough to complete the disconnect operation.
To account for slow operate times as a result of cold weather or low battery
voltage, set the 89CSTm time 10 to 15 percent longer than the expected
operate time. This guarantees that the disconnect switch has fully operated
before the 89CLSm signal is removed. When the 89CSTm seal-in timer
expires, 89CSIm asserts, or when the disconnect switch normally open contact
closes (89CLm asserted), the 89CLSm output deasserts. This completes an
open-to-close cycle of the Disconnect Close Logic; the disconnect open logic
in Figure 12.2 behaves in the same manner.
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