At present

thermal power units with large and medium capacity in East China power grid are all participating in operation of automatic generation control (AGC)

enhancing safety and stability

as well as the frequeney quality of the said power grid

but having a certain negative influence of load flucturation in a large range resulting from AGC upon the service life of said thermal power units. Results of caculation show that a close relationship existing between the load variation rate and the service life of units. The life expenditure of rotor during the time of load rising and dropping with a load variation rate of 5MW/min is 47 times of that with a load variation rate of 3MW/min. The influence of load flucturation with high frequency and narrow range under normal operation of units upon service life of the rotor is very small

being negliglble.