What are the functions of high-pressure speed regulating valve and low-pressure speed regulating valve of steam turbine?

It is to adjust the steam intake and control the speed of steam turbine. The steam turbine of feed water pump in power station has two steam sources (usually reheat cooling section and four-stage extraction, or fresh steam and four-stage extraction). The small steam turbine adopts four-stage extraction as the main steam, and the speed of the steam turbine is controlled by adjusting the steam flow through the low-pressure governor valve. When the working condition of large steam turbine changes and the four-stage extraction steam cannot meet the feed water flow, the control system will automatically switch to the high-pressure steam source (reheat, cold section or new steam). If it is an internal switching unit, it will enter the small turbine through the high-pressure speed regulating valve to increase the speed of the small turbine as steam supplement. If it is an external switching unit, there is no high-pressure speed regulating valve.