ABB 615 Series ANSI, Technical Manual

Page: 488 / 713

1MAC050144-MB C
Section 7
Control functions
615 series ANSI 481
Technical Manual
already is in the right position, the maximum pulse length is given. Note that the Pulse
length setting does not affect the length of the trip pulse.
Control methods
The command execution mode can be set with the Control model setting. The alternatives
for command execution are direct control and secured object control, which can be used
to secure controlling.
The secured object control SBO is an important feature of the communication protocols
that support horizontal communication, because the command reservation and
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 following 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 cancelling: cancels the controlling of a selected object.
In direct operate, a single message is used to initiate the control action of a physical device.
The direct operate method uses less communication network capacity and bandwidth than
the SBO method, because the procedure needs fewer messages for accurate operation.