ABB RELION 620 Series Technical Manual page 714

Section 9
Control functions
708
interlocking signals can be transferred with a bus. All secured control operations require
two-step commands: a selection step and an execution step. The secured object control is
responsible for the several tasks.
• Command authority: ensures that the command source is authorized to operate the
object
• Mutual exclusion: ensures that only one command source at a time can control the
object
• Interlocking: allows only safe commands
• Execution: supervises the command execution
• Command canceling: cancels the controlling of a selected object.
In direct operation, a single message is used to initiate the control action of a physical
device. The direct operation method uses less communication network capacity and
bandwidth than the SBO method, because the procedure needs fewer messages for
accurate operation.
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Selected
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to operate
GUID-80B170A6-C091-4F8E-BF99-919B8A180917-ANSI V1 EN
Figure 356: Control procedure in SBO method
1. Send reservation to other terminals
2. Receive response
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1MAC504801-IB E
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620 series ANSI
Technical Manual