Thermal power plant

Abstract

The invention relates to a thermal power plant including a turbine (1, 2, 3) operated using at least one water-steam-loop (4), and a generator (5) driven by said turbine (1, 2, 3). According to the present invention, means (6, 7, 8, 9, 10) for cooling said generator (5) are provided, which means (6, 7, 8, 9, 10) are de signed for extracting condensate from said water-steam-loop (4), transporting it to said generator (5) and returning it into said water-steam-loop (4).

Description

FIELD OF THE INVENTION [0001] This invention relates in general to a thermal power plant including a turbine operated using at least one water-steam-loop, and a generator driven by said turbine. The thermal power plant referred to can e.g. be a conventional steam power plant, a combined gas and steam power plant or a nuclear power plant. BACKGROUND OF THE INVENTION [0002] Thermal power plants known in the prior art comprise a turbine, which is supplied with pressurized steam from a steam raising unit. The pressurized steam expands in the turbine and thereby causes the turbine to rotate. This rotational motion is transferred via a drive shaft to an electric generator, which generator converts the mechanical energy into electrical energy. The inevitable energy losses during the energy conversion in the generator lead to an undesirable heating of the generator. In order to avoid excessive generator temperatures, it is necessary to cool the generator during operation. In the prior art t...

AI Technical Summary

Benefits of technology

[0005] The present invention is based on the insight, that by using condensate from the water-steam-loop for cooling the generator and returning the heated up condensate into the loop, the excess thermal energy produced by the generator can be transferred into the water-steam-loop with minimal energy loss. This measure improves the thermal efficiency of the overall thermal power plant significantly.

[0006] It is advantageous, if the means for cooling the generator comprise an extraction device for extracting the condensate from the water-steam-loop, wherein the extraction device is arranged close to a location of the lowest condensate temperature within the water-steam-loop. Therewith the condensate transported to the generator is essentially of the lowest temperature available within the water-steam-loop. This allows for an optimum cooling effect of the generator. The generator can therefore be cooled to a relatively low temperature, which increases its efficiency. Further, no or very little additional cooling, like air cooling etc., needs to be provided to the gen erator, which results in the thermal energy produced by the generator being transferred to the water-steam-loop to a very high degree. This again leads to a high thermal efficiency of the overall power plant.

[0008] Additionally, it is advantageous if the extraction device is arranged close to a condensate pump. A condensate pump is usually positioned immediately after the condenser in order to move the condensate on in the loop. If the extraction device is arranged as above, it is due to the proximity to the condenser ensured, that the temperature of the condensate is very low, and further the momentum provided to the condensate by the condensate pump may be of assistance for moving the condensate to the generator.

[0010] In addition, it is advantageous if the means for cooling the generator further comprise a return device for returning the condensate into the water-steam-loop after the condensate has been heated up during cooling the generator. The thermal energy extracted from the generator in the form of an elevated temperature of the condensate is mo st effectively fed back into the water-steam-loop by returning it into the loop before pre-heating takes place. As the condensate in the loop is at this point still of a relatively low temperature, the injection of higher temperature condensate has a signi ficant effect on the resulting temperature of the combined condensate. In this case the generator takes over part of the function of the low pressure pre -heating device, as the condensate entering the device already has an elevated temperature. Thereby, a higher temperature can be achieved for the condensate after passing the low-pressure pre-heating device.

[0012] It is further expedient, if the means for cooling the generator comprise a circulation pump for transporting the extracted condensate to the generator. This measure speeds up the circulation of the extracted condensate and therefore ensures a sufficient stream of condensate to circle to the generator in order to provide for the required cooling effect. By adjusting the pumping speed of the circulation pump and therewith its suction effect, it is further possible to control the amount of condensate extracted from the water-steam-loop. It is therefore not required to provide a special mechanical diverting device within the extraction device in order to divert enough condensate towards the generator. The amount of condensate required for cooling the generator can rather be easily controlled by adjusting the operating speed of the circulation pump.

Problems solved by technology

Further, no or very little additional cooling, like air cooling etc., needs to be provided to the gen erator, which results in the thermal energy produced by the generator being transferred to the water-steam-loop to a very high degree.

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