Siemens SIMATIC S7-1500 System Manual page 206

Failure scenario
①
②
③
④
⑤
Figure 6-50
Sequence of events
1. The PROFINET ring is interrupted at 2 points at a time interval of ≤ 1500 ms.
2. The redundant system switches to an undefined system state: The primary CPU remains in
the RUN operating state. The backup CPU becomes the primary CPU and remains in RUN
operating state.
3. The two primary CPUs continue to exchange process data with the accessible IO devices.
4. The redundancy of the system is defective. The redundant system is in an undefined system
state. The undefined system state can lead to dangerous states in the process.
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF
Primary CPU
Backup CPU
PROFINET ring → interrupted a 2 locations
IO device ET 200MP
IO device ET 200SP
2 cable interruptions in the PROFINET ring (within ≤ 1500 ms)
WARNING
Undefined system state of the S7-1500R redundant system at the same time as a
cable interruption in the PROFINET ring at 2 points within ≤ 1500 ms.
Lay the PROFINET cables so that they are securely protected from damage. PROFINET
cables should also always be laid separately from each other. This makes simultaneous
damage to the PROFINET cables (within ≤ 1500 ms) unlikely.
Application planning
6.5 Failure scenarios
205