Siemens SIMATIC S7-1500 System Manual page 194

Sequence of events
1. Both PROFINET lines in PROFINET ring 1 on the primary CPU fail. The redundant system will
not execute a primary-backup switchover. The redundant system will remain in the RUN-
Redundant system state.
2. The redundant system selects an alternative connection over the backup CPU and the
PROFINET ring 2. This allows the redundant system to reach the R1 devices again.
3. The redundancy of the system is restricted. The restriction has no effect on the process. If
another system component fails, the S7-1500R/H redundant system can fail as a result.
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: The PROFINET ring 1 is open. No backup AR.
Note
To get detailed diagnostics information, evaluate the diagnostics buffer.
Solution
Replace the defective PROFINET cables. 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
193