5.7
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Control
Disconnect Logic
89OIP
m
When Relay Word bit 89OIPm asserts, a disconnect switch operation is in prog-
ress. Relay Word bit 89OIP asserts when the states of the 89BMm and 89AMm
Relay Word bits are the same, i.e., both asserted or both deasserted.
89CLB
m
This Relay Word bit is used for bus-zone protection and asserts when the discon-
nect is no longer open (89BMm deasserted).
89CL
m
When Relay Word bit 89CLm asserts, the disconnect switch is closed.
89OPN
m
When Relay Word bit 89OPNm asserts, the disconnect switch is open.
Disconnect Switch Status and Alarm Logic Processing
Figure 5.3 shows the Disconnect Switch Status and Alarm Logic. Inputs to this
logic are the normally open (89AMm) and normally closed (89BMm) disconnect
switch auxiliary contacts.
To understand the logic in Figure 5.3, consider an open-to-close operation. The
first disconnect operation scenario looks at a successful open-to-close disconnect
switch operation; a successful close-to-open operation is similar. In the open
state, 89AMm is deasserted and 89BMm is asserted. Once a close command is
initiated in the relay, the disconnect switch starts to move and 89BMm deasserts.
When 89BMm deasserts, the 89ALPm pickup timer starts to time. With 89BMm
deasserted, the state of the disconnect switch cannot be determined, because both
disconnect switch auxiliary contacts are deasserted. Set the 89ALPm timer longer
than the expected undetermined disconnect state time, but less than the 89CSTm
or 89OSTm seal-in timers. If the 89ALPm timer expires, the 89ALm Relay Word
bit asserts. Relay Word bit 89ALm asserts when the disconnect operation does
not complete successfully. When the 89ALPm timer begins timing, the operation
in progress, Relay Word bit 89OIPm, and Relay Word bit 89CLBm assert. The
89CLBm Relay Word bit is for bus-zone protection, this bit asserts when the
89BMm input deasserts.
During the disconnect switch operation-in-progress condition, Relay Word bits
89CLm and 89OPNm are both deasserted because the state of the disconnect
switch is undetermined. Once the disconnect switch auxiliary contact Relay
Word bit 89AMm asserts, the condition has been met to declare the disconnect
switch closed. When 89AMm asserts, the 89CLm Relay Word bit asserts,
89ALPm stops timing, Relay Word bit 89OIPm deasserts, and Relay Word bit
89CLBm remains asserted. This sequence completes a successful open-to-close
disconnect switch operation.
The second disconnect operation scenario is for an unsuccessful open-to-close
operation, which, until 89ALPm starts timing, is identical to the successful oper-
ation in the previously discussed first scenario.
During operation of the 89ALPm timer, the disconnect switch begins moving.
The close disconnect switch output signal 89CLSm clears upon expiration of the
89CSTm seal-in timer. The logic then provides the disconnect switch additional
time to complete the close operation, in case some inertia from the motor rotor
keeps the disconnect motor in motion. By setting the 89ALPm
timer longer than
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