ABB Relion 670 Series Applications Manual page 531

1MRK 511 401-UUS F
energized, the SMAI function delivers a magnitude of zero with good quality for all the channels.
Thus, this has no effect on a busbar protection, nor protections in an 1 1/2 circuit breaker
configuration.
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Figure 237: Configuration of current inputs using SMAIs in a 1 1/2 circuit breaker application.
Procedure to bring protections back into service and enable maintenance of
a faulty merging unit
1. Disconnect bay
2. Energize binary input, block of bay. Protections are now back in service.
3. Maintenance of the merging unit can start.
Procedure to bring bay back into service after maintenance of a merging
unit
1. Energize merging unit.
2. De-energize binary input block of bay. Protections are now back in service.
3. Reconnect bay.
20.3.3 Bay out of service for maintenance
When a bay need maintenance and has energized merging unit connected, it is always a risk to get
unplanned interruptions in the auxiliary power supply which may lead to unwanted blocking of
protections.
This can be resolved by using the same ACT configuration recommendations and procedures as
described in section
Bay control REC670
Application manual
SMAI function blocks exist in different cycle times, and all the SMAI blocks that
receive SV streams from the merging units must have the block input signal
configured in the same way to get the correct behavior.
Faulty merging unit for bay in
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service.
Section 20
Station communication
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