“Polling rate overrun” message appears because of the configuration done between PLC and the OFS server. OFS server is requesting too much data and the PLC is not able to respond in a timely manner.

Fine-tuning on the system is required to optimize performance with the following parameters.

• OFS Max and OFS Pending Channels configuration*
• OPC Client update rate*
• The total number of requests required to exchange the complete set of data (Noticed).
• Time requires to access the complete set of Data (Best, Worst, Average Time) (Noticed).
• Update Criteria of variables at the Scada screen (Active on Demand) *
• CPU and Ethernet communication module request handling capability (Noticed).
• PLC Scan cycle, (Current, Min, and Max) (Noticed).
• Reduce the PLC scan cycle that allows the PLC to handle more requests per minute*.

Note: * Fine tune these parameters and in line with the system capabilities. After changing the parameters closely observing the feedback from the OFS Server under the Diagnostics window until the system is stabilized.

Used the link below for the documents that provide the details steps of fine-tuning.
https://www.se.com/ww/en/download/document/EIO0000001730/

Released for: Schneider Electric Saudi Arabia