Solutions For Communication - Siemens SIMATIC PCS 7 Function Manual

Fault-tolerant Solutions in PCS 7

3.3 Solutions for communication

3.3 Solutions for communication
Introduction
In this section, you will learn about the redundancy concepts for the various levels of the
process control system.
Requirements for communication systems
The availability of a process control system is not only determined by the automation system,
the environment also plays a considerable role. This includes not only the operator control and
monitoring components but also a high-performance communication system that connects the
management level to the process level and the process level to the field level.
Distributed control systems are also needed in the manufacturing and processing automation.
Complex control tasks are broken down into smaller, simpler steps with distributed form. The
demand for communication between distributed systems increases.
High-performance, comprehensive communication system is needed to fulfill this demand. The
communication connections between the systems involved should be redundant.
Local networks (LAN) form the basis of the communication system. The following are options
that can be implemented based on the specific system requirements:
● Electrical
● Optical
● Electrical/optical combination
The communication connections are grouped in three areas:
● Terminal bus
● Plant bus
● Fieldbus
In PCS 7, we recommend that the bus systems are set up in a ring structure. The ring structure
makes the bus "fault-tolerant", since it can compensate for the failure of a bus line.
Redundant communication connections
Redundant communication connections can be formed on all levels of the process control
system.
When a communication error occurs, communication automatically switches over from the
active connection to the backup connection. Both connections use the same media and
protocols. The failover has no effect on the user program running in the CPU.
44
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA