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AWWA CSC95004
- Intermixing Local Automatic Control With Remote Supervisory Control
- Conference Proceeding by American Water Works Association, 01/01/1995
- Publisher: AWWA
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Many SCADA systems are configured so that their programmable logic controllers (PLCs) operate autonomously, performing most automatic process control on a local basis. Under this arrangement, the SCADA host computer approaches a purely supervisory role and the process control decisions are relegated to the PLCs in the field. This approach has several advantages, such as freeing the host to do graphics, reports, and archiving without the added burden of executing sometimes very complex control strategies, and eliminating the host as a single point of system failure. Distributing control decisions among several capable PLCs while leaving the SCADA host to do its specialized functions makes good sense in many applications. There are several techniques that can be used during SCADA system design to maximize the benefits of distributed local control while minimizing the corresponding headaches.