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What does the TSE upper margin and TSE lower margin mean in steam turbine? i.e. sometimes while rolling, the machine doesn't accelerate up to the rated speed as desired that means it sometimes trips on dn/dt.

Dear Vipul,

TSE (Turbine stress Evaluator) upper margin & lower margin indicates allowable limits during the ST in operation (run up, loading, deloading of steam turbine). There are inputs from CV/ESV metal temp (50% & 100%), shaft temp, casing temp, HP main steam Temp. DT(a) (Differential Temp) is calculated from the inputs & compared with allowed DT (p)set limits. Difference between DT(p) & DT(a) is known as margin, upper on positive side & lower on negative side.

Using either the turbine stress evaluator (TSE) or the stress monitoring function of the turbine stress control system (TSC), non-steady-state thermal stresses to which the steam turbine is exposed during start up and shut down and as a result of changes in heat input to components during power operation are acquired and compared with the permitted limits.

The margins obtained from this comparison define the stress and set the bounds for permitted temperature load. Evaluation of measured temperatures recording and action of the calculated margins on the set point control for the turbine controller allow an optimum mode as regards both degree of component fatigue and economical operation.

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