5.5
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Control
Disconnect Logic
To account for slow operate times because 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 sig-
nal is removed. When the 89CSTm seal-in timer expires, 89CSIm asserts, or 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 5.2 behaves in the same manner.
Disconnect switch status and alarm logic in Figure 5.3 generates Relay Word bit
89ALm. When Relay Word bit 89ALm asserts, a disconnect alarm condition
exists. The 89ALm Relay Word bit ensures that the close or open signal does not
remain asserted when a disconnect switch alarm condition exists. When Relay
Word bit 89ALm asserts or the seal-in timer expires, the 89CLSm or 89OPEm
signals deassert.
When a close operation is inadvertently initiated with the disconnect switch
already closed, and the 89CRSm SEL
OGIC control equation is set as defaulted
(89CLm OR 89CSIm), the asserted 89CLm Relay Word bit (close status) will
block the seal-in circuit before the timer expires. This will deassert the 89CLSm
Relay Word bit, which drives the disconnect switch motor. In this way, 89CLSm
asserts for only one processing interval.
If an open command was sent within the 89CSIm time, an open and close signal
could be sent to the disconnect switch at the same time. The 89CLSm Relay
Word bit input to the Disconnect Switch Open Logic guarantees that open and
close commands are not transmitted to the disconnect switch simultaneously.
When the 89CLSm Relay Word bit deasserts, an open command can be per-
formed. The 89OBLm SEL
OGIC control equation provides an additional custom-
izable method for blocking the initiation of a close command. The Relay Word
bit 89OPEm, and 89CBLm inputs to the Disconnect Switch Close Logic serves
the same purpose.
Disconnect Switch Status and Alarm Logic
The disconnect switch auxiliary contacts are inputs to the Disconnect Switch Sta-
tus and Alarm Logic as shown in Figure 5.3. SEL
OGIC control equation 89AMm
is the input for the normally open an auxiliary contact, and SEL
OGIC control
equation 89BMm is the input for the normally closed Form B auxiliary contact.
For the Status and Alarm Logic to function correctly, wire the Form A and Form
B contacts each to separate inputs on the relay. When ordering a relay, consider
the number of inputs required for the disconnects being controlled. The number
of auxiliary contacts for some systems may require that the relay be configured
with additional I/O boards.
Disconnect operations are possible with only one auxiliary contact input, but
with this implementation the Status and Alarm Logic will not provide accurate
Alarm, Operation in Progress, or Bus-zone protection reporting. When only one
auxiliary contact is available for input, set one SEL
OGIC control equation to the
available auxiliary contact input and invert the other SEL
OGIC control equation:
89AMm := IN102
89BMm := NOT IN102
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