Power-load unbalanced(PLU) protection of turbine generator can prevent overspeed of the turbine

but unnecessary protection action easily causes unit tripping and other accidents. According to the theoretical model of steam turbine

the PLU simulation model of an ultra-supercritical 1 050 MW unit was established and applied to analyze the overspeed protection action and the variations of the rotor speed of the unit under conditions with full load rejection. The simulation results show that

both the PLU of the unit and the overspeed protection control(OPC) can realize overspeed protection. The system with OPC reached the maximum speed(3 192 r/min)

which was higher than that of the system with OPC and PLU(3 150 r/min) when full load rejection took place

and the system with PLU and OPC only actioned about 0.16 s earlier than the system with OPC. It can be said that the overspeed protection function of the PLU is overlapped with OPC in this unit

and it is possible for the PLU to cause serious accidents due to misoperation. Therefore

if the turbo-generator is equipped with both OPC and PLU

and the PLU only acts to prevent overspeed of the unit

it is recommended that the PLU can be eliminated on the premise of optimizing the OPC logic.