Torsional Vibrations of the Steam Turbine Shaft Line and Estimation of the Residual Life of Its Elements

Abstract

A comparative quantitative assessment of the damage and residual life of the shaft line elements for differ-ent types of high-power steam turbines at the end of their design life is made by mathematical modeling. The analysis covers all elements of the shaft line: from the steam turbine Central pump to the turbine generator ex-citer. The simulated circuit includes turbo generators, transformers, gate converters, AC and DC power lines. When modeling, an approach is used from the position of proper coordinates, which provides maximum meth-odological consistency of the models of the listed devices and allows you to directly reproduce electromagnetic and mechanical transients with the determination of instantaneous values of currents, voltages, electromagnet-ic and torsional moments. To estimate damage, we used the deformation criterion for soft and hard loads in the zone of low-cycle and force criterion in the zone of multi-cycle fatigue. The influence of the number of starts and running time of a steam turbine on the damage and residual life of its shaft elements is studied. When de-termining the remaining life, in addition to starts, other abnormal operating modes of the turbo generator were taken into account during the turbine operating time: short circuits and their disconnections, unsuccessful high-speed automatic re-activation, subsynchronous resonance due to both the operation of the control system of the PPT and the automatic generator excitation regulator. The influence of attenuation of electromagnetic transients in the generator and damping of torsional vibrations on the degree of reduction of the residual life of the shaft elements is analyzed. The results obtained can be used for a comprehensive solution of the issue of further operation of steam turbines that have spent their design life.