Testing Steam Turbines in Combined Cycle Applications

ASME Performance Test Code 6.2 for testing of Steam Turbines in Combined Cycle Applications has been approved by the Board of Performance Test Codes and will be issued in 2005. PTC 6.2 provides procedures for the accurate testing of a steam turbine in a Combined Cycle application with or without supplementary firing and in cogeneration applications. The procedures for testing a Rankine cycle steam turbine in a Combined Cycle application differ from those used to test a Rankine cycle steam turbine in a cycle with regenerative feedwater heating because of differences in cycle configuration and test objectives. PTC 6.2 provides procedures for testing and calculating corrected turbine-generator output performance, not corrected heat rate. The Code contains rules and procedures for the conduct and reporting of steam turbine testing, including requirements for pretest arrangements, testing techniques, instrumentation, methods of measurement, and methods for calculating test results and uncertainty. This paper will focus on challenges that have been faced with conducting performance tests on steam turbines in combined cycles in the past, and how the Code has addressed these challenges. Challenges are driven primarily by the cycle configuration, operating practices, and the basis of guarantees. Subjects to be addressed in the paper include test instrumentation, test objectives, test calculations, and test uncertainty.