SIMATIC PCS 7 Process Control System - Siemens

■ Overview
Fault-tolerant automation systems are used to reduce the risk of
production failures. The higher investment costs for fault-tolerant
automation systems are frequently negligible compared to the
costs resulting from production failures. The higher the costs of
a production failure, the more worthwhile it is to use a fault-tolerant
system.
Fault-tolerant automation systems can be mounted in a UR2-H
compact rack with divided backplane bus or in two separate
racks (UR1 or UR2). The design in two racks allows physical
separation of the redundant subsystems, e.g. by a fireproof partition.
Fault-tolerant automation systems can be used on their own in a
plant configuration, or together with standard and safety-related
automation systems.
© Siemens AG 2008
Automation systems
Fault-tolerant automation systems
■ Design
Fault-tolerant automation systems for SIMATIC PCS 7 are available
as preassembled and tested all-in-one systems (AS bundles)
at no extra charge.
Depending on the type of automation system, the RAM of these
AS bundles varies as follows:
AS type Main memory
AS 412H 768 KB (512 KB for program and 256 KB for data)
AS 414H 2.8 MB (1.4 MB each for program and data)
AS 417H 30 MB (15 MB each for program and data)
Runtime licenses
Each AS bundle is already provided as standard with the
SIMATIC PCS 7 AS Runtime license for 100 process objects
(PO). The number of process objects can be extended by additional
Runtime licenses for 100, 1000 or 10000 POs. The process
objects of additional Runtime licenses can be added to process
objects which already exist. The number and type (e.g. 100 or
1000) of additional Runtime licenses are irrelevant. The AS Runtime
licenses are administered on a SIMATIC PCS 7 engineering
system or in the SIMATIC PCS 7 BOX.
Connection of process I/Os
Several PROFIBUS DP lines with distributed process I/Os can be
operated on each sub-AS through the internal PROFIBUS DP interface
or by using additional communications processors.
• The ET 200M remote I/O stations are connected via two
IM 153-2 High Feature interface modules on a special bus
module to two redundant PROFIBUS DP segments.
• The intelligent field devices on the PROFIBUS PA are connected
over a DP/PA link to two redundant IM 153-2 High
Feature interface modules.
• Non-redundant PROFIBUS DP devices, e.g. ET 200S
distributed I/O devices, can be connected to the redundant
PROFIBUS DP over the Y-link.
These configurations can also be mixed together.
Communication over the plant bus
The AS 412H, AS 414H and AS 417H automation systems are
connected as standard by one communications processor per
sub-AS to the plant bus.
The plant bus can be implemented in the form of a ring structure,
which can also be configured with redundant architecture if the
availability requirements are high. When there are two redundant
rings it makes sense to use two communications processors
per sub-AS and to distribute their connections between the two
rings (4-way connection). Double faults such as failure of the
OSM/SCALANCE switch on ring 1 with simultaneous interruption
in the bus cable on ring 2 can thus be tolerated.
Siemens ST PCS 7 · Update November 2008
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