To keep the high main steam pressure of the nozzle governing steam turbine under partial load conditions

weaken the influence of low efficiency of governing stage on flow efficiency of high pressure cylinder

and effectively improve the economic efficiency of the steam turbine under partial load conditions

this paper proposes a new nozzle governing method with overload valve regulation

on the basis of analyzing the existing governing methods of steam turbine. Taking a supercritical 660 MW unit as an example

the paper analyzes the thermal characteristics and economic performance of the steam turbines using the new governing method of nozzle governing with overload valve regulation and bypass governing. The results show that

the economy of the turbine adopting the new regulation technology is similar to that employing the bypass governing near 90% THA condition

while as the unit load decreases

the economy of the turbine adopting the new regulation technology is better than that employing the bypass governing

and this advantage gradually increases. For the units of which the load ranges from 40% THA to 85% THA within the whole year

applying the new regulation technology can reach a higher economic efficiency.