Long term effect of power system unbalance on the corrosion fatigue life expenditure of low pressure turbine blades

Usually, the effect of power-system unbalance is based on the limitation of generator thermo-rating. According to this limitation the protection scheme for system unbalance is designed. However, the authors find that the long-term effects of power system unbalance may become a cause of fatigue damage on low-pressure (LP) turbine blades even though the system unbalance is still within the limitation of generator thermal rating. As it result, turbine blades are possibly unprotected by traditional system unbalance protection schemes. In particular, for the last three stages of blades that are made of AISI-403 material and with vibration modes closing to the double-frequency avoidance zone, the long-term cumulative corrosion fatigue life expenditure of blades may relatively large due to the inevitable corrosive operating environment with NaCl. Therefore, the influence of power system unbalance on turbine blades might be essential and would not always be neglected