Hi everyone,

I work with two S7-1515R-2 in a redundancy system - communication in ring topology with 2 cpus, 1 switch and 2 remotes - and because of process needs they must always work 24/7. From lessons learned from the past we inserted alarms to detect any fault in the ring – if an ethernet connector is disconnected we are able to check where the fault occurred and fix it before the ring comms breaks. Recently we had a system fault that resulted in communication loss to both remotes for a short period of time. After analysis we are confident to say it was a communication fault, but no alarms regarding a Ring Fault occurred. Technician at the place noted that an ethernet connector was not fully connected in one of the remotes and after troubleshooting there were no more issues. No alarms at the time appeared at the HMI log indicating a communication fault associated to this connector, not even days before the issue, and nobody touched that panel. When the fault occurred two alarms that I have never seen appeared, both associated to communication:

I searched here at Siemens forums and could not find anything related. This log was saved from the HMI log. Extracting the log from the CPU did not bring good results, since the event seems to have been already overwritten. The alarms that are normally associated to communication losses that I’m familiar with are “R-CPU sync connection not redundant” or “Media redundancy error _ - MRP ring open”.

Does anyone know what those alarms indicates? If a non-detected ethernet cable/connector had an issue, could it mess up the ring communication to a point that a second failure was not required? Since trying to simulate the issue just showed the same Ring Open alarms that are already configured, is there any other alarm or configuration that could be set to identify this issue before it happens?

Thank you very much,

Rodrigo Pereira