Combined with four stage load rejection test completed in Zhuhai power plant on unit No 1 of 2×700 MW units

the designed charaterisitics of over speed controller（OPC） of this unit has been analyzed

discussing the requiments for designing the circuits of over speed protection.The result of load rejection test of this unit shows

despite the designed OPC has a number of electronic circuits

but the compensation for power non-equilibrium has been introduced into the speed-controlling circuit

enabling not only the governor valve has fast-closing function

but also the OPC has good adaptability to load reject cases at different loads.