Abstract: Various water-saving and energy-saving measures are widely implemented in power project construction. Especially in the preliminary design phase of power plant, from technical scheme design to equipment model selection, from environmental protection to labor safety, water conservation, energy saving and environmental protection are always emphasized. In order to ensure that the power plant from the beginning of construction to the power plant put into operation the design of advanced technology. Environmental protection and energy saving, power plant development to create the necessary conditions. This paper focuses on power plant water supply system design energy-saving measures to promote the application of energy-efficient circulating water pump Keywords: energy efficient economic flow pump performance curve natural ventilation cooling tower, circulating water pump, circulating water pipelines and pipe fittings is an important component of the circulating water system in power plants In part, studying the system plan to determine the optimal system configuration in the preliminary design of the power plant is of positive significance for reducing the construction cost. The most important part of the design of circulating water system is the reasonable choice and configuration of natural ventilation cooling tower and circulating water pump. In the construction of circulating water system, they have the highest investment cost, the most complicated construction and the greatest impact on the total investment of power plant. Directly affect the unit cost of power engineering construction and plant investment recovery period. The optimal design of the water supply system is the basis for the selection of the system solutions. Among them, the annual cost of the circulating pump motor is the most important factor affecting the design of the water supply system. Under the premise of ensuring the safety of turbine running at full capacity, how to reduce the annual cost of electric motor is worth every engineering designer's thinking. This article will face the above issues for research. Starting from reducing the annual cost of the motor, the working efficiency of the circulating pump and the motor is studied. Under the premise of meeting the various operating conditions of the turbine (including the pure condensing condition, the maximum pumping condition and the rated pumping condition), the circulating pump Equipped with motor reactive power, improve motor efficiency. In recent years, with the advent of the country's new round of economic construction climax, a large number of 135MW domestic EHV and intermediate reheat units have been built all over the country. In Gansu Jinchuan Company Thermal Power Plant, Shandong Huatai Thermal Power Plant, Shandong Liyan Power Plant, Xuzhou Power City Power Plant and Shandong Binzhou Weiqiao Thermal Power Plant, we have designed 16 135MW units to select the circulating water pump in circulating water system of 135MW unit. Long-term economic security operation for the purpose of promoting the use of energy-efficient circulating pump. 1. Brief Introduction of High-efficiency and Energy-saving Circulating Water Pumps 1.1 High-efficiency and Energy-saving Circulating Water Pumps Overview: Most of domestic circulating water supply systems of 100MW, 125MW and 135MW units adopt the conventional arrangement of one unit with two circulating pumps. This configuration mode In line with "thermal power plant technical regulations, norms," ​​also in line with the power system industry "hydraulic technical requirements", widely used in power plant design. Economic analysis of power plant construction projects found that the thermal power plant using a conventional two-pump circulating water system layout of the higher cost of running the system, there are some shortcomings in the design are mainly: circulating pump design point parameters deviate from the system operating values, the pump low efficiency. The circulating pump that has been put into operation and found that the circulating power plant is generally existed in the power plant operating efficiency except for part of the time most of the time circulating pump is not running high efficiency, most of the time the pump efficiency is only about 60%, it is clear that it does not belong to the pump High efficiency range. Pump operation mode is not sensitive to the change of circulatory system flow rate. For a single operation of the turbine, the turbine condenser cooling water volume fluctuates greatly with the annual seasons; for variable operating conditions of the turbine, along with the steam turbine extraction volume Increase, the system significantly reduce the amount of cooling water. The thermal power plant using a conventional two-pump mode setting exists for most of the year running a water pump insufficient water supply capacity of two pumps is too large, the pump is difficult to regulate the operation is not conducive to the formation of the most favorable steam turbine vacuum , In vain to waste electricity, in order to fundamentally solve the problem of circulating water pump configuration and system flow changes, improve the operating efficiency of circulating water pump, production and development of energy-efficient water pump is inevitable. 1.2 Characteristics of High-efficiency and Energy-saving Circulating Water Pump This paper introduces the characteristics of a new type of G series circulating water pump from the perspective of high efficiency and energy saving of circulating water pump. The emphasis is put on the application of G48Sh new circulating water pump in the design of 135MW unit. G48Sh new circulating pump design parameters and plant circulating water system, the actual resistance parameters and kiss, the pump running more efficient. More than 100 G48Sh circulating pumps put into operation were sampled and tested. The actual efficiency of G48Sh pumps was 84-88%. Compared with the conventional mode of 135MW units, the actual efficiency of one machine with two pumps of the same model 48Sh-22 was improved 25%. G48Sh new circulating pump with motor using bipolar number, double speed operation. According to the annual season different steam turbine condenser cooling water volume changes drastically, by adjusting the motor motor pole number and speed motor output power changes, so that the circulating pump water supply, water pressure changes. Increased the flexibility of the system adjustment, to minimize plant electricity load. For example, a G48Sh high-efficiency energy-saving pump runs in high speed in summer and 3000 tons / hour more than two 48Sh-22 pumps at the same pump power. In winter, one G48Sh high efficiency energy-saving pump runs at low speed, Under the condition that the system water supply is quite high, the power of the pump equipped motor is reduced from 1080KW to 680KW, the power drop is over 30%, equivalent to 2.3 million kWh saved per pump per year. The introduction of G48Sh high efficiency and energy saving circulating water pump optimizes the hydraulic conditions of the circulating water system and widens the variation range of the high efficiency section of the water pump so as to ensure the actual operating efficiency of the circulating water pump at two different rotational speeds not less than 85% The efficiency of work. The introduction of the G48Sh high efficiency and energy saving circulating water pump has changed the conventional design concept of capacity configuration mode of two turbines with two circulating pumps (hereinafter referred to as "one machine and two pumps") and proposed the design concept of large capacity and small pump configuration. Large pumps have high speed, low speed, small pumps also have high speed, low speed, which combined a variety of pump operating conditions, and each other standby. Basically meet the steam turbine working conditions change conditions. High efficiency and energy saving circulating pump horizontal pump casing, operation, maintenance is very convenient. 1.3 High-efficiency energy-saving circulating pump configuration In Jinchuan Thermal Power Plant in Gansu, Shandong Huatai Thermal Power Plant, Shandong Liyan Power Plant, Xuzhou City Power Plant and Shandong Binzhou Weiqiao Thermal Power Plant, we have designed 18 sets of 135MW unit domestic EHV, intermediate reheat unit . These power plants have a common characteristic, basically enterprises spontaneous use, enterprises in addition to a stable power demand but also have a certain heating load, heating load fluctuations in large enterprises. Making the circulating water system in the power plant circulating water drastically changed. In the absence of heating load, the heating unit is basically operating in pure condensing conditions, which often occur in the summer of each year. With the advent of winter, the heating load and living heating load increase, so that the unit heating load greatly increased, in extreme cases, the unit will exceed the rated pumping conditions. Most of these enterprises are located in North China, Northeast China and Northwest China, heating longer, with a fixed heating period of 4-6 months each year, a few years longer heating period. For such a long period of time, the unit operates with steam extraction and heating, which makes the circulating flow of power plants run at a lower time for a long time. Considering the long-term economic operation requirements of power plants, the water supply flow of the circulating pump and the high efficiency range of the lift are very long. Taking 135MW heating unit as an example: When steam turbine VWO condition is in summer, steam condensing capacity of steam turbine is 324.17t / h and circulating capacity of one unit is 19640t / h; when steam turbine rated extraction condition, Steam condensate volume of 223.36t / h, a unit of 12274 t / h of circulating water; steam turbine at maximum extraction conditions, condensing steam turbine capacity of 142.66t / h, the unit of circulating water is 4700 t / h. Circulating water system flow from 4700t / H - 19000T / H changes, according to the conventional capacity of the pump is arranged to meet the minimum heat load of the cooling water unit configuration circulating pump flow 9800T / H-11700T / H, water supply head about 18.0- 21.5 meters, two pumps run in parallel. In the rated extraction conditions, a pump running, due to the reduction of circulating water, the system's water resistance drops, the pump flow 12274T / H, head will drop to 15.0-16.0 meters, the steam turbine in the maximum extraction conditions, To meet the requirements of circulating water system to run a pump, due to a substantial reduction in water supply, the pump head greatly increased, resulting in a cooling tower water directly to increase the water flow device with a sink, water flow in the filler on the heat exchange The reduction of time reduces the cooling effect of the cooling tower. Of course, the effect of reducing the heat exchange between the filler and the filler does not draw too much attention in the winter, but the pump operation will definitely move out of the efficient range of the pump. The working efficiency of the pump is reduced and the reactive power of the motor is wasted. As circulating pump motor power 710KW, long-term operation is not conducive to power plant energy conservation. In this case requires a new pump configuration mode, it is necessary to meet the large flow, high lift requirements but also to meet the low flow requirements of low lift, there