Shaft seal steam supply pipeline heating system of steam turbine generator unit and control method thereof

The invention discloses a shaft seal steam supply pipeline heating system of a steam turbine generator unit and a control method thereof. The shaft seal steam supply pipeline heating system comprisesa high-medium pressure cylinder front shaft seal and a high-medium pressure cylinder rear shaft seal which are connected to a shaft seal mother pipe through a first steam inlet branch pipe and a second steam inlet branch pipe respectively, wherein a first control valve and a second control valve are arranged on the first steam inlet branch pipe and the second steam inlet branch pipe respectively,a first heating device and a second heating device are arranged on the first steam inlet branch pipe and the second steam inlet branch pipe respectively, and a first drain control valve and a second drain control valve are further connected to a first branch pipeline and a second branch pipeline at the outlet ends of the first control valve and the second control valve respectively; and one branchpipeline of the shaft seal