Siemens Simatic S7-1500R System Manual page 86

Sequence of events
1. The two redundancy connections (fiber-optic cables) are interrupted ≤ 1500 ms apart.
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 PROFINET 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.
Diagnostics
System state and operating states after the failure of both redundancy connections:
● Redundant system → System state defective (undefined: Each H-CPU is in the RUN-Solo
system state).
● Primary CPU → RUN operating state
– MAINT LED → yellow light: The H-system is not in the RUN-Redundant system state.
● Primary CPU (previously backup CPU) → RUN operating state
– MAINT LED → yellow light: The H-system is not in the RUN-Redundant system state.
Note
To get detailed diagnostics information, evaluate the diagnostics buffer.
Solution
Please note the following solution:
Note
Before you replace the defective redundancy connections, you must switch both H-CPUs to
the STOP operating state. Only then repair the redundancy connections. Switch the H-CPUs
back to the RUN operating state.
You can find additional information on the procedure in the section Replacing defective
redundancy connections (Page 261).
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA
WARNING
Undefined system state of the S7-1500H redundant system when two redundancy
connections are interrupted ≤ 1500 ms apart.
Lay the redundancy connections so that the fiber-optic cables are securely protected
from damage. Also make sure when laying the cables that the two redundancy
connections are always separate from each other. This makes simultaneous damage to
the redundancy connections (< 1500 ms apart) unlikely.
No partner CPU has been found in the H-system.
No partner CPU has been found in the H-system.
Application planning
3.5 Failure scenarios
85