Decentral fieldbus distribution in power stations

The application

Cooling towers  

Cooling towers

Fieldbus-based automation systems are increasingly being used in power stations. As such, the most modern power station automation systems not only offer integrated auxiliary power consumption via IEC 61850, but also end-to-end connection of process engineering via Profibus DP.

Standardized diagnostics, end-to-end communication and standardized engineering tools allow the infrastructure to be flexibly adapted to optimize processes.

System structure for power station automation system

Power station system structure

Example system structure for a power station automation system (SPPA-T3000, Siemens AG)

Availability of the station

Redundancy plays a key role in achieving 100% availability of the power station. Starting with the redundant CPUs of controllers and redundant bus masters in the automation system (master redundancy), redundant fiber optic lines (line redundancy) are frequently integrated into the actual power station process, where process engineering components such as motor management modules, actuators, sensors, decentral control units and I/O modules connect directly to the automation level via Profibus DP.  

Technical background information

With Profibus DP, there is a dependency between the transfer rate and the maximum cable length for copper cabling (see table). If longer Profibus DP lines are required for the process, you can increase the cable length of the copper cabling by using appropriate repeaters. Another way of increasing distances is to use media converters to convert wired into fiber-optic-based transmission. FO converters facilitate very large transmission distances while ensuring maximum interference immunity and potential separation as well as extremely fast data transfer rates.

Transmission speedConductor length (copper)
9.6 kbps – 187.5 kbps1,000 m
500 kbps400 m
1.5 Mbps200 m
3, 6, 12 Mbps100 m

The solution

Copper/FO transmission overview  

Overview of copper/FO transmission

Phoenix Contact offers you a wide range of media converters to implement various network topologies for copper or fiber optic cabling. These devices allow you to realize typical network structures – such as line, star and tree structures as well as redundant fiber optic rings – very flexibly. The integrated bar graph provides continuous, updated information on the transmission quality of the fiber-optic line. When and if a critical level is reached, an early warning is output via a switching contact before a system failure occurs.

We also supply individual fieldbus distribution stations in conjunction with a redundant supply concept for auxiliary voltage. These stations are used e.g. to accommodate fiber optic-based, redundant Profibus lines and wired sub-distribution up to the actuators in the process environment. To this end, the Quint ORING redundancy module monitors redundancy in the supply line to the fieldbus distribution station. Process devices can also be supplied directly from the fieldbus distribution station using device circuit breakers. The potential distribution required is realized using modular terminal blocks with Push-in connection technology, which allows the conductors to be plug connected without the need for using tools. If needed, you can implement fieldbus distribution station connections using Plug-and-Play connectors. This reduces assembly costs and significantly improves fault tolerance.

Fieldbus distributing station

Fieldbus distributing station

Example of a fieldbus distributing station

Your advantages at a glance

  • Increased availability thanks to a redundant link to the main control level
  • Monitoring of the fiber optic path transmission
  • Connectors on the housing for copper and fiber optic cables
  • Individually adaptable and ready-for-assembly control cabinet solution
  • Individual fault messages via PROFIBUS for:
    – Limited availability of redundant voltage
    – Triggering of a device circuit breaker
    – Undershooting of system reserve capacity for the fiber-optic line


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