Reduction of the Temperature Measuring Uncertainty in the Hot Steam Area of Power Plants

Project Number 236

A provably small uncertainty of the temperature measurement allows smaller safety margins in relation to the maximum admissible steam temperatures. Ultimately, higher temperatures will be possible, which will allow efficiency to be improved. According to the results of previous projects now available, a reduction in measuring uncertainty from 5 to 1 K is feasible. This has been achieved through the development of miniature fixed point cells, whose characteristic smelting and solidification temperatures are used as calibration standards.

The bases for these thermocouples were established in the research project "Relatively error-free measurement of the main steam temperature in the range 605 to 650 °C”: This project is part of the VGB Joint Research Programme "Kraftwerks-Optionen: Material und Messtechnik-Entwicklungen sowie deren Tests unter Betriebsbedingungen bei 650 °C" (Power plant options: Material and measuring developments and also their tests under operating conditions at 650 °C) (KOMET 650). As part of further VGB research projects, and also on behalf of E.ON, the Technical University of llmenau has developed various miniature fixed point thermocouples with automated evaluation units for use in the hot steam range from 520 to 540 °C and from 540 to 580 °C for the controlled recalibration of the corresponding temperature measuring circuits under operating conditions for continuous use.

The following areas will be investigated in detail as part of this research project:

  • Equipping the thermocouples with a second temperature sensor for controlling the internal heating and for measured value transmission during the calibration cycle.
  • Development and testing of a complex measuring transducer for evaluating thermal stress, control and evaluation of the calibration cycles and connection to control systems.
  • Use of function samples in the overall measuring arrays (thermocouple, measuring transducer, control system connection) to prove the ability to function, with practical experience feedback.

The project will run from December 1, 2002, to November 30, 2003 at the lnstitut für Prozessmess- und Sensortechnik der TU IImenau under Dr. Frank Bernhard and will be monitored by a working group of the VGB Working Panel "Control and Instrumentation and IT”.