ABB Relion 670 Series Applications Manual page 392

Section 14
Control
• Over-Current
• Total block via settings
• Total block via configuration
• Analog input error
• Automatic block via settings
• Automatic block via configuration
• Under-Voltage
• Command error
• Position indication error
• Tap changer error
• Reversed Action
• Circulating current
• Communication error
Master-follower method
When the master is blocked, the followers will not tap by themselves and there is consequently no
need for further mutual blocking. On the other hand, when a follower is blocked there is a need to
send a mutual blocking signal to the master. This will prevent a situation where the rest of the
group otherwise would be able to tap away from the blocked individual, and that way cause high
circulating currents.
Thus, when a follower is blocked, it broadcasts a mutual block on the horizontal communication.
The master picks up this message, and blocks its automatic operation as well.
Besides the conditions listed above for mutual blocking with the circulating current method, the
following blocking conditions in any of the followers will also cause mutual blocking:
• Master-follower out of position
• Master-follower error (No master/More than one master)
General
It should be noted that partial blocking will not cause mutual blocking.
TR8ATCC (90), which is the "source" of the mutual blocking will set its AUTOBLK output as well as
the output which corresponds to the actual blocking condition for example, IBLK for over-current
blocking. The other TR8ATCCs (90) that receive a mutual block signal will only set its AUTOBLK
output.
The mutual blocking remains until TR8ATCC (90) that dispatched the mutual block signal is de-
blocked. Another way to release the mutual blocking is to force TR8ATCC (90), which caused
mutual blocking to Single mode operation. This is done by activating the binary input SNGLMODE
on TR8ATCC (90) function block or by setting the parameter
local HMI or PST.
TR8ATCC (90) function can be forced to single mode at any time. It will then behave exactly the
same way as described in section
horizontal communication messages are still sent and received, but the received messages are
ignored. TR8ATCC (90) is at the same time also automatically excluded from the parallel group.
Disabling of blockings in special situations
When the Automatic voltage control for tap changer TR1ATCC (90) for single control and TR8ATCC
(90) for parallel control, function block is connected to read back information (tap position value
and tap changer in progress signal) it may sometimes be difficult to find timing data to be set in
TR1ATCC (90) or TR8ATCC (90) for proper operation. Especially at commissioning of for example,
386
"Automatic voltage control for a single
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1MRK 511 401-UUS F
OperationPAR to Off from the built-in
transformer", except that
Bay control REC670
Application manual
SEMOD159053-329 v4