Abstract:Steam turbine is high speed rolling mechanism, overrotatingspeed will cause serious accident. Steam turbine power and load unbalance protection unit (PLU) is an important aspect of steam turbine overrotatingspeed protection, and was considered in many practices. Took a 1000MW unit power plant in Zhejiang as example, the design principle of HITACH HIACS5000M’s PLU was analyzed by hardware and logical. The commissioning method of HITACH HIACS5000M’s PLU was provided.

Keywords:steam turbine；over speed protection;power load unbalance protect, control system