Study of the influence of the participation of a supercritical unit in the primary frequency modulation on the service life of a steam turbine

The authors have conducted a study of the influence of the participation of a supercritical high power unit in the primary frequency modulation of the power grid on the loss in service life of the steam turbine, established a finite element model for the fatigue life of the rotor of the turbine under various operating conditions and calculated and analyzed the transient temperature field and elastic and plastic stress field of the rotor when the unit was taking part in the primary frequency modulation of the power grid. It has been found that when the load changes in a range of 10%, the maximum stress on the surface of the shaft at the dangerous location is 82. 18 MPa, the variation value of the stress is 69. 18 MPa, the maximum stress at the center of the shaft is less than 20 MPa and the variation value of the stress is less than 17 MPa, showing that the stress is very low and the thermal stress is also very small. The primary frequency modulation has a small influence on the temperature variation at all stages in HP and MP cylinder and the thermal stress and the influence on the service life of the unit can be neglected, thus the unit is capable of safely taking part in the primary frequency modulation of the power grid.