Condensate and feedwater system of steam power plant and operation method for the same

A condensate and feedwater system of a steam power plant, comprising:

• a deaerator that heats and deaerates condensate water generated in a condenser, by extraction steam of a steam turbine, and temporarily stores the heated and deaerated condensate water;
• a heater disposed on a condensate line between the condenser and the deaerator, the heater being configured to heat the condensate water generated in the condenser, by extraction steam of the steam turbine;
• a deaerator water level control valve disposed on an upstream side of the heater in the condensate line, the deaerator water level control valve being capable of controlling water level of the condensate water in the deaerator;
• a deaerator circulation pump that returns condensate water flowing out from the deaerator to a part of the condensate line between the heater and the deaerator;
• an apparatus configured to be supplied with part of the condensate water flowing from the heater toward the deaerator, through a supply line branched from the condensate line;
• a supply line shutoff valve disposed on the supply line, the supply line shutoff valve being configured to switch between communication and interruption of the supply line;
• and
• a controller that controls opening/closing of the supply line shutoff valve and controls driving/stopping of the deaerator circulation pump, wherein
• the controller
• puts the supply line shutoff valve into an open state and puts the deaerator circulation pump into a stopped state, in normal operation, and
• closes the supply line shutoff valve from the open state at the normal operation and at least temporarily drives the deaerator circulation pump from the stopped state at the normal operation, in condensate throttling in which supply of the extraction steam to the heater and the deaerator is reduced as compared to that at the normal operation and the deaerator water level control valve is closed.