Largest UK coal-fired power plant installs FOUNDATION fieldbus system
England’s Drax Power Station, reported to be the largest, cleanest, and most efficient coal fired power plant in Selby, North Yorkshire, is installing FOUNDATION fieldbus based Rosemount temperature transmitters and interface units on one of its units. The system transmits data from over 500 temperature monitoring points on one selected boiler and turbine pair. Drax Power and their refurbishment contractor, Capula, chose the Rosemount 3420 fieldbus module to interface with their Schneider PLC host system.
Drax Power Station uses six steam boilers to generate up to 4000MW. At current output levels, this one plant supplies enough power to meet 7% of UK demand. The main fuel is pulverized coal, but Drax Power has developed the capability to burn alternative fuels such as biomass blended with the coal. The temperature sensors are mainly thermocouples used for monitoring the boiler, superheater, and re-heater, plus turbine and generator temperatures in high-density arrangements. They can detect any irregularities or “hot spots.”
The monitoring thermocouples are linked individually to one of the 70 Rosemount 848T eight-input temperature transmitters. Up to 13 of the Rosemount 848T units can be powered from one FOUNDATION fieldbus segment, transmitting the temperature measurements from up to 104 sensors along two wires. The link between the site fieldbus segments and the host PLC system is provided by seven Rosemount 3420 fieldbus interface modules. Each can power up to four separate FOUNDATION fieldbus segments and retransmit the data over a Modbus RS485 serial connection. The Rosemount 3420 unit also provides an Ethernet port for separate connection of a supervisory PC, which can be used to configure the unit as needed. This assists in sensor maintenance and allows access to the diagnostic data available over the fieldbus to monitor sensor and transmitter performance.
While providing Drax Power with a neat and accurate system solution, the extra capabilities of the Rosemount 3420 allow further investigation of any unusual heat patterns during tests of alternative fuels and firing systems. It also reduces the complexity and time needed for rewiring during the current retrofit. Once installed, F fieldbus segments around the boiler will allow addition of further test equipment or other sensors for plant condition monitoring, with relatively simple configuration to transmit data back to the supervisory systems.
--Control Engineering Daily News Desk
Peter Welander , process industries editor
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