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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 89CST
m
time 10 to 15 percent longer than the expected operate time. This
guarantees that the disconnect switch has fully operated before the 89CLS
m
sig-
nal is removed. When the 89CST
m
seal-in timer expires, 89CSI
m
asserts, or the
disconnect switch normally open contact closes (89CL
m
asserted), the 89CLS
m
output deasserts. This completes an open-to-close cycle of the Disconnect Close
Logic; the Disconnect Open Logic in
behaves in the same manner.
Disconnect switch status and alarm logic in
89AL
m
. When Relay Word bit 89ALm asserts, a disconnect alarm condition
exists. The 89AL
m
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 89AL
m
asserts or the seal-in timer expires, the 89CLS
m
or 89OPE
m
signals deassert.
When a close operation is inadvertently initiated with the disconnect switch
already closed, and the 89CRS
m
SEL
OGIC
control equation is set as defaulted
(89CL
m
OR 89CSI
m
), the asserted 89CL
m
Relay Word bit (close status) will
block the seal-in circuit before the timer expires. This will deassert the 89CLS
m
Relay Word bit, which drives the disconnect switch motor. In this way, 89CLS
m
asserts for only one processing interval.
If an open command was sent within the 89CSI
m
time, an open and close signal
could be sent to the disconnect switch at the same time. The 89CLS
m
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 89CLS
m
Relay Word bit deasserts, an open command can be per-
formed. The 89OBL
m
SEL
OGIC
control equation provides an additional custom-
izable method for blocking the initiation of a close command. The Relay Word
bit 89OPE
m
, and 89CBL
m
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
OGIC
control equation 89AM
m
is the input for the normally open an auxiliary contact, and SEL
OGIC
control
equation 89BM
m
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:
89AM
m
:=
IN102
89BM
m
:=
NOT IN102
Summary of Contents for SEL-421-4
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