Siemens SIMATIC S7-1500 System Manual page 196

Sequence of events
1. Both PROFINET lines between the R1 devices fail.
2. The redundant system will remain in the RUN-Redundant system state: The primary and
backup CPUs remain in the RUN-Redundant operating state. The roles of the primary and
backup CPUs do not change.
3. The redundant system selects an alternative connection to the lower R1 device via the
backup CPU. This allows the redundant system to reach all IO devices in the line topology
again.
4. The redundancy of the system is restricted. The restriction has no effect on the process.
If another system component or another network segment fails, the S7-1500R/H redundant
system will fail as a result:
If the PROFINET cable is also interrupted at another point in the line topology, an IO device
will fail.
Note
Separate routing of the PROFINET lines
When routing the PROFINET cables, make sure that you always route the PROFINET cables
between the R1 devices and to the H-CPUs separately. This makes simultaneous damage
unlikely and increases the availability of the redundant system.
Diagnostics
System state, operating states and error displays after the failure of both PROFINET cables:
• Redundant system → RUN-Redundant system state
• Primary CPU/Backup CPU → RUN-Redundant operating state
– MAINT LED → yellow light: No backup AR.
Note
To get detailed diagnostics information, evaluate the diagnostics buffer.
Solution
Replace the two PROFINET lines. You can find additional information on the procedure in the
section Replacing defective PROFINET cables (Page 451).
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
Application planning
6.4 Redundancy scenarios
195