Pgm Redundancy-Specific Operations - Honeywell Experion PKS User Manual

5 PROFIBUS GATEWAY MODULE (PGM) BLOCK

5.6 PGM redundancy-specific operations

Tip
For complete information on the Redundancy functionality, refer to the following documents.
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About switchover
A switchover is triggered immediately upon the detection of a fault in the primary or upon the receipt of an
operator command.
Depending on the switchover trigger, the original primary PGM attempts to reboot into the secondary role, but
this PGM cannot immediately participate in another switchover operation. After the new secondary reboots into
the secondary role, it must first perform and complete initial-synchronization before another switchover is
allowed.
During the switchover time, the PROFIBUS slave devices lose connection to the master. However, the behavior
of the slave devices during a switchover depends on their configuration. For most of the devices, you can
configure a time during which they hold their outputs. However, there are devices that lose their outputs
immediately. Therefore, from a PGM redundancy standpoint, selection of the I/Os plays a vital role.
Conditions that result in a switchover
The following conditions result in a switchover.
• Issuing a Switchover command.
• Issuing a Shutdown command on the primary PGM.
• Both FTE cables removed from the primary PGM.
• The primary PGM is removed from the IOTA.
• The primary PGM is restarted.
• The primary PGM is failed.
• The PROFIBUS cable is disconnected from the primary PGM.
Conditions that do not result in a switchover
The following conditions do not result in a switchover.
• Redundancy cable between the primary and the secondary PGM is disconnected or broken.
• Both FTE links to the secondary PGM are lost.
• Loss of power to the secondary PGM.
• Failure of the secondary PGM.
• Removal of the secondary PGM module from its IOTA.
• Inserting a different PGM module into a powered secondary IOTA.
• If the PGM is provided with a single FTE link and that link is disconnected or broken.
Conditions that result in loss of synchronization
The following conditions result in loss of synchronization in a synchronized or standby redundant PGM pair.
• Issuing the Disable Sync command (from the primary or the secondary platform FB).
• Redundancy cable between the primary and the secondary PGM is lost.
• Loss of input power to the secondary PGM.
• Failure of the secondary PGM.
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