Estimation of exhaust steam enthalpy and steam wetness fraction for steam turbines based on data reconciliation with characteristic constraints

• Characteristic constraints of steam turbines are introduced in a data reconciliation problem.
• Application to the steam turbine system of a real-life power plant using design and operational data.
• Effect of uncertainty reduction is enhanced for all measurements.
• Better estimates of exhaust steam enthalpy and steam wetness fraction are achieved.

Wetness fraction of exhaust steam is important to the economy and safety of steam turbines. Due to lack of commercially available measurement technologies, it is usually obtained from model based calculation via other measurements. However, accuracy of relevant measurement data is usually unsatisfactory due to limits of measuring instruments, and data reconciliation can be applied to improve the accuracy of these measurements. Traditionally, balance constraints of steam turbines are mostly considered in data reconciliation, and results of previous studies illustrate that there is still potential for further improvement. In this work, we present a generalized data reconciliation approach with both balance and characteristic constraints for estimation of wet steam parameters in steam turbines, with case studies on a real-life 1000 MW coal-fired power plant. Results show that uncertainty reduction is enhanced for all measurements. Better estimates of exhaust steam enthalpy and steam wetness fraction can be therefore obtained after data reconciliation.