I'm working on different methods to communicate between a HMI and PLC. The communication will happen over a longer distance, and I want it to be "safe", as in connection that doesn't break. So far i have only come up with one good solution; do this communication via a OPC-server. Is this the best way, or do you guys know a better alternative?

 

This depends in part on which PLC and what HMI, also on the media used to communicate through. If this is copper or FO Ethernet, then OPC is the best available for most systems today.

Of course if the distance is more than Ethernet can handle you may want to look at smoke signals or runners.

Pertinent detail in your question will likely bring a more relevant answer.