SIEMENS
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Siemens IK PI · 2015
PROFIBUS
Electrical networks (PROFIBUS PA)
Introduction
3
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Overview
SIMATIC Fieldbus Calculator
Direct interfacing of the devices in the field, especially in the
hazardous area, together with the information content of the
communication, are of significant importance in the process
industry. PROFIBUS PA, which permits both digital data trans-
mission and the power supply on a two-wire line with the intrinsi-
cally-safe MBP transmission technology (Manchester Coded;
Bus Powered) is tailored to these requirements. It is optimally
suitable for direct integration of solenoid valves, sensors, and
pneumatic actuators positioned in operating environments up to
Ex zone 1/21 or 0/20 into the process control system.
The typical response time of a transmitter of approx. 10 ms
indicates that short cycle times can be achieved with the
PROFIBUS PA even in the case of a segment configuration with
up to 31 devices. Practically all typical applications of the
process industry can be implemented, both in small and large
plants. Bidirectional communication and high information
content allow enhanced diagnostics for fast and exact fault
detection and elimination. The standardized communications
services guarantee interoperability and replaceability between
multi-vendor field devices and remote configuration of the field
devices during operation.
Safety communication with the PROFIsafe profile
The PROFIsafe profile allows seamless integration of safety
communication into the PROFIBUS PA. You need not configure
a separate safety bus for your safety-related applications. The
PROFIBUS PA with the PROFIsafe profile is incorporated in
"Safety Integrated for Process Automation". This comprehensive
range of products and services from Siemens for failsafe, fault-
tolerant applications in the process industry offers you attractive
and cost-effective alternatives to separate safety systems.
Redundant architectures
You can define the degree of redundancy separately for the
controller, fieldbus and I/O levels of your plant depending on the
automation task and the derived safety requirements, and match
them to the field instrumentation (Flexible Modular Redundancy,
FMR). You can find an overview of the redundant architectures
of PROFIBUS PA under "Design".
Network transition PROFIBUS PA to PROFIBUS DP
The PA link is preferred as the gateway from PROFIBUS PA to
PROFIBUS DP. When using the PA link, the transmission rate on
the PROFIBUS DP is independent of the lower-level PROFIBUS
PA segments. The configuration of the PA link depends on the
fieldbus architecture. The types of coupler described in the
section "PA routers" can be used for the configuration. With a
small volume of data (small quantity structure) and low time
requirements, the DP/PA coupler can also be operated in stand-
alone mode as a gateway.
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Benefits
Advantages provided by distributed field automation with
application of the PROFIBUS PA profile included low hardware
overhead, cost-effective engineering, increased operational
safety and problem-free maintenance. These advantages are
underlined by the following features:
•
Modularity and uniformity from the sensor up to the control
level permit new plant concepts
•
Implementation of intrinsically-safe applications through use
of the fieldbus in hazardous areas
•
Redundant PROFIBUS PA architectures (ring and line topol-
ogies with coupler redundancy) support Flexible Modular
Redundancy (FMR) from the automation system (controller)
down to a PA field device
•
Safety-related and fault-tolerant applications with low device
and cabling requirements
•
Reduced configuration costs through simple, central
engineering of the field devices (PROFIBUS PA and HART
with SIMATIC PDM, also cross-vendor)
•
Simple installation using two wire cable for common power
supply and data transmission
•
Reduced commissioning costs through simplified loop check
•
Low servicing costs thanks to simple wiring and compre-
hensive diagnostics facilities
© Siemens AG 2014