Steam power plants have an average service life of 40 years. There are many power plants still operating with the original supervision systems. These plants were equipped with control, protection, and supervision systems, which were available at the time. Over the last 20 years, steam turbine control/protection systems’ capabilities have been greatly improved. New hardware and improved software are available today to extend the life of existing turbines. For example, older turbines were originally equipped with casing metal temperature measurements or with so-called mechanical temperature probes for stress supervision. These measurements assist operators during manual run-up and loading of the turbine. Today’s upgraded supervision systems use the original sensors to measure the turbine metal temperature. Existing temperature signals are used as inputs to the electronic modules. These modules calculate the actual stresses in rotors and/or casings and acceptable margins. In cases where the calculated stress exceeds the pre-set limits, the run-up or loading gradient is automatically reduced, thus optimizing startup time of the steam turbine and resulting in optimal usage of the turbine’s life. Based on many years of experience in steam turbine design and service, standard proven algorithms are used to determine stress calculations. Automatic stress limiters can be installed. Acceptable stresses as well as actual stresses and margins can be displayed on the Operator Station (HMI) and recorded. Based on these records the lifetime assessment can be performed. The operator can select either slow, normal or fast startup, which will influence the lifetime consumption.

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