At one site we've installed a WinCC HMI, connected to a S7-400 FS PLC. Now every once in a while (6 months) unexpected alarms and trips show up, both on the actual alarm as well as on the historical alarm side. The trending shows no change of values and the machine stays running. Based on the incorrectly displayed trip bits it should shut down. I'm confident the behavior derives from the HMI and the PLC still does the job safely, but I can't lay may finger on the cause of these alarms. I thought of a fiberoptic linkage (between PLC and HMI) issue, but they insists all is OK there. Looks like an incorrect buffer change. Anyone suggestions?
Unexpected alarms in WinCC
- Thread starter Bemstra
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