Compressed air supply system for multi-reactor nuclear power plant

Abstract

The present application discloses a compressed air supply system for a multi-reactor nuclear power plant. The compressed air supply system comprises: at most two compressed air stations (10) connected via a transmission pipe network (20) to N nuclear power units, each compressed air station (10) comprising four parallel-connected primary air compressors (11) and four dryers (12) correspondingly connected to the four primary air compressors (11), the four dryers (12) being arranged in parallel. The invention satisfies the reliability requirements of a downstream user with regard to the compressed air supply system, and reasonably reduces device configuration and cost.

Description

FIELD

[0001] The present invention belongs to the technical field of nuclear power technology, and in particular to a compressed air supply system for a multi-unit nuclear power plant.BACKGROUND

[0002] When the nuclear island and conventional island system equipment of a nuclear power plant are in operation or under maintenance, instrument compressed air is needed to supply air to pneumatic valves and instruments, and service compressed air is needed to supply air to pneumatic tools and process purges. The demand for the consumption of compressed air is continuous, but also has periodic or sudden fluctuations. The peak consumption of service compressed air is generally during unit maintenance. A drop in pressure or insufficient air supply of instrument compressed air affects the normal operation of pneumatic valves and is also related to the normal operation of nuclear power plants. Therefore, high reliability requirements are placed on instrument compressed air, and system design will give priority to ensuring the supply of instrument compressed air.

[0003] As shown in FIG. 1, one of the solutions currently adopted by the compressed air supply system of nuclear power plants is: the main air compressor station in the compressed air production part is shared by two units, equipped with three air compressors + dryers, and compressed air wet tanks and compressed air dry tanks are respectively configured before and after the dryers. During normal operation and maintenance of the two units, one or two air compressor units are in operation, and the other is on standby. The cooling water for the air compressor units is introduced from unit 1 and unit 2 respectively, and supplied through the header pipe, serving as backup for each other. The power supply comes from busbar of unit 1 and busbar of unit 2. Two air compressor units are connected to the busbar of unit 1, and one air compressor unit is connected to the busbar of unit 2. The air quality coming out of the main air compressor station can meet the service compressed air demand and can be directly connected to the service compressed air distribution system. The compressed air coming out of the main air compressor station is further dried by two sets of dryers installed in each nuclear island and then enters the instrument compressed air distribution system. Two emergency air compressors are also installed in front of the nuclear island dryers, equipped with emergency power supplies. The pressure of the compressed air production system is automatically controlled. When the header pipe pressure drops to a certain value, the standby air compressor is started first. If the pressure continues to drop, the air supply of the service compressed air system is cut off to ensure instrument compressed air. If the pressure continues to drop, the emergency air compressor is started. If the pressure continues to drop, the compressed air for the conventional island and other users' instruments is cut off to ensure the air demand of the nuclear island users.

[0004] The main drawback of this technical solution is the high equipment cost. The two units are equipped with a total of 7 air compressors and dryers. The emergency air compressor is basically in standby status and requires daily maintenance and regular testing.

[0005] As shown in FIG. 2, the second solution currently adopted by the compressed air supply system of nuclear power plants is: the main air compressor station in compressed air production part is shared by all six units in the plant, and is equipped with six air compressors + dryers. Compressed air wet tanks and compressed air dry tanks are respectively arranged before and after the dryers. During normal operation and maintenance of the six units, 4 to 5 air compressor units are in operation, and the other 1 to 2 are on standby. The cooling water for the air compressor units is introduced from unit 1 and unit 2 respectively, and supplied through the header pipe, serving as backup for each other. The power supply comes from busbar of unit 1 and busbar of unit 2. The three air compressor units are connected to the busbar of unit 1, and the three air compressor units are connected to the busbar of unit 2. The air quality coming out of the main air compressor station can meet the service compressed air demand and can be directly connected to the service compressed air distribution system. The compressed air coming out of the main air compressor station is further dried by two sets of dryers installed in each nuclear island and then enters the instrument compressed air distribution system. Two emergency air compressors are also installed in front of the nuclear island dryers, equipped with emergency power supplies. The pressure of the compressed air production system is automatically controlled. When the header pipe pressure drops to a certain value, the standby air compressor is started first. If the pressure continues to drop, the air supply of the service compressed air system is cut off to ensure instrument compressed air. If the pressure continues to drop, the emergency air compressor is started. If the pressure continues to drop, the compressed air for the conventional island and other users' instruments is cut off to ensure the air demand of the nuclear island users.

[0006] The main drawbacks of this technical solution are the high equipment cost and lower air supply reliability than Solution 1. The six units are equipped with a total of 18 air compressors and dryers. The emergency air compressors are basically in standby status and require daily maintenance and regular testing. The power supply and cooling water sources for the main air compressor station equipment are limited to the first two nuclear power units. Due to the early construction progress, they cannot be supplied from the units to be built later. At the same time, the service life of the units to be built later will also be reduced. In particular, during the maintenance of a busbar, there are only three air compressor units available, which cannot meet the air needs for normal operation and maintenance of the units. If equipment failure is taken into account, the air supply gap will be even greater, and it will be necessary to rely on the start-up of emergency air compressor units to ensure the instrument air supply, affecting the unit availability. Maintenance of the header pipe isolation valve in the plant area will affect the normal operation of multiple units.SUMMARY

[0007] The technical problem to be solved by the present invention is to provide a compressed air supply system for a multi-unit nuclear power plant.

[0008] The technical solution adopted by the present invention to solve the above technical problem is: constructing a compressed air supply system for a multi-unit nuclear power plant, including at most two compressed air stations connected to N nuclear power units through an air transmission network, each of the compressed air stations includes four main air compressors connected in parallel and four dryers correspondingly connected to the four main air compressors, and the four dryers are arranged in parallel.

[0009] In some embodiments, two compressed air wet tanks arranged in parallel are configured between the four main air compressors and the four dryers.

[0010] In some embodiments, two compressed air dry tanks arranged in parallel are configured between the air transmission ends of the four dryers and the air transmission network.

[0011] In some embodiments, the air transmission ends of the two compressed air dry tanks of each compressed air station are connected to an air transmission main pipe; The air transmission network includes a first air transmission header pipe and a second air transmission header pipe, the first air transmission header pipe is respectively connected to the air transmission main pipes of all the compressed air stations and instrument compressed air distribution systems of all the nuclear power units; The second air transmission header pipe is respectively connected to the air transmission main pipes of all the compressed air stations and the same nuclear power first air transmission parent pipe is respectively connected to the air transmission main pipe and service compressed air distribution system of all the nuclear power units.

[0012] In some embodiments, the first air transmission header pipe is connected to the air transmission main pipe through a first connecting pipe; and the second air transmission header pipe is connected to the air transmission main pipe through a second connecting pipe.

[0013] In some embodiments, an automatic shut-off valve is provided between the air transmission main pipe and the second connecting pipe.

[0014] In some embodiments, first isolation valves are respectively provided on both sides of the first air transmission header pipe at the connection with the first connecting pipe.

[0015] In some embodiments, second isolation valves are respectively provided on both sides of the second air transmission header pipe at the connection with the second connecting pipe.

[0016] In some embodiments, the first air transmission header pipe is connected to each of the instrument compressed air distribution systems through a first branch pipe; Third isolation valves are respectively provided on both sides of the first air transmission header pipe at the connection with the first branch pipe.

[0017] In some embodiments, the second air transmission header pipe is connected to each of the service compressed air distribution systems through a second branch pipe; Fourth isolation valves are respectively provided on both sides of the second air transmission header pipe at the connection with the second branch pipe.

[0018] In some embodiments, each of the instrument compressed air distribution systems includes a first pipeline, and a first compressed air tank is provided on the first pipeline; One end of the first pipeline is connected to the first branch pipe, and the other end of the first pipeline is connected to air-consuming equipment of a nuclear island user.

[0019] In some embodiments, each of the instrument compressed air distribution systems includes a second pipeline, and at least two second compressed air tanks connected in parallel are provided on the second pipeline; One end of the second pipeline is connected to the first branch pipe, and the other end of the second pipeline is connected to air-consuming equipment of a conventional island user.

[0020] In some embodiments, a control valve is provided on the second pipeline between the connection point of the first pipeline and the first branch pipe and the second compressed air tank.

[0021] In some embodiments, each of the instrument compressed air distribution systems includes a third pipeline, one end of the third pipeline is connected to the downstream of the second compressed air tank, and the other end of the third pipeline is connected to air-consuming equipment of other users.

[0022] In some embodiments, each of the service compressed air distribution systems includes a fourth pipeline, and a third compressed air tank is provided on the fourth pipeline; One end of the fourth pipeline is connected to the second branch pipe, and the other end of the fourth pipeline is connected to air-consuming equipment of a conventional island user.

[0023] In some embodiments, each of the service compressed air distribution systems includes a fifth pipeline, one end of the fifth pipeline is connected to the upstream of the third compressed air tank, and the other end of the fifth pipeline is connected to air-consuming equipment of a nuclear island user.

[0024] In some embodiments, each of the service compressed air distribution systems includes a sixth pipeline, one end of the sixth pipeline is connected to the downstream of the third compressed air tank, and the other end of the sixth pipeline is connected to air-consuming equipment of other users.

[0025] In some embodiments, a row of power busbar is configured for every two main air compressors and the corresponding two dryers.

[0026] In some embodiments, a single compressed air station is equipped with two rows of cooling water pipelines.

[0027] In some embodiments, N = 2, 4 or 6; When N=2, the number of the compressed air station is one; When N=4 or 6, the number of the compressed air stations is two.

[0028] In some embodiments, at least three pressure sensors are provided on the first connecting pipe, wherein at least two of the pressure sensors are configured to trigger the start-up of at least one of the standby main air compressor and the standby dryer when the pressure value is lower than a first set value, and at least two of the pressure sensors are configured to trigger the unloading of one of the main air compressor and the dryer when the pressure value is higher than a second set value.

[0029] The implementation of the present invention has the following beneficial effects: the compressed air supply system for a multi-unit nuclear power plant, including at most two compressed air stations connected to N nuclear power units through an air transmission network, each of the compressed air stations includes four main air compressors connected in parallel and four dryers correspondingly connected to the four main air compressors, and the four dryers are arranged in parallel. On the basis of meeting the reliability requirements of downstream users for the compressed air supply system, the equipment configuration and cost are reasonably reduced.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work. In the drawings: FIG. 1 is a schematic structural diagram of a first compressed air supply system for a nuclear power plant in the related art; FIG. 2 is a schematic structural diagram of a second compressed air supply system for a nuclear power plant in the related art; FIG. 3 is a schematic structural diagram of a compressed air supply system for a multi-unit nuclear power plant in some embodiments of the present invention; and FIG. 4 is a schematic structural diagram of a compressed air supply system for a multi-unit nuclear power plant in some other embodiments of the present invention. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", and "tail" are based on the directions or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific direction. They are only for the convenience of describing the technical solution, and do not indicate that the device or element referred to must have a specific direction. Therefore, they should not be understood as limiting the present invention.

[0032] It should also be noted that, unless otherwise clearly stipulated and limited, terms such as "install", "link", "connect", "fix", and "set" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" on the other element, or one or more intervening elements may also be present. The terms "first", "second", "third", etc. are only used to facilitate the description of the present technical solution and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the following description, for the purpose of explanation rather than limitation, specific details such as particular system structures and technologies are provided to provide a thorough understanding of the embodiments of the present invention. However, it will be apparent to one skilled in the art that the present invention may also be embodied in other embodiments without these specific details.. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0034] Referring to FIG. 3, the present invention shows a compressed air supply system for a multi-unit nuclear power plant, including at most two compressed air stations 10 connected to N nuclear power units through an air transmission network 20, each compressed air station 10 includes four main air compressors 11 in parallel and four dryers 12 correspondingly connected to the four main air compressors 11, and the four dryers 12 are arranged in parallel. In some embodiments, the compressed air station 10 can also be defined as a compressed air production system or a main air compressor station.

[0035] Preferably, a control isolation valve may be provided on the pipe section of the air outlet of each main air compressor 11.

[0036] In some embodiments, two compressed air wet tanks 13 arranged in parallel are configured between the four main air compressors 11 and the four dryers 12 .

[0037] In some embodiments, two compressed air dry tanks 14 arranged in parallel are configured between the air transmission ends of the four dryers 12 and the air transmission network 20. The compressed air dry tanks 14 can be used to store compressed air.

[0038] In some embodiments, the air transmission ends of the two compressed air dry tanks 14 of each compressed air station 10 are connected to an air transmission main pipe 15. The air transmission network 20 includes a first air transmission header pipe 21 and a second air transmission header pipe 22. The first air transmission header pipe 21 is respectively connected to the air transmission main pipes 15 of all compressed air stations 10 and instrument compressed air distribution systems 30 of all nuclear power units.

[0039] The second air transmission header pipe 22 is respectively connected to the air transmission main pipes 15 of all the compressed air stations 10 and the same nuclear power first air transmission parent pipe 21 is respectively connected to the air transmission main pipe 15 and service compressed air distribution systems 40 of all nuclear power units.

[0040] In some embodiments, the first air transmission header pipe 21 is connected to the air transmission main pipe 15 through a first connecting pipe 16; the second air transmission header pipe 22 is connected to the air transmission main pipe 15 through a second connecting pipe 17 .

[0041] Furthermore, an automatic shut-off valve 18 is provided between the air transmission main pipe 15 and the second connecting pipe 17. When the pressure is low, it automatically cuts off the supply of compressed air for plants, giving priority to ensuring the needs of users of instrument compressed air. When the pressure of the compressed air is lower than 0.76 MPa, the service compressed air supply is cut off by the automatic shut-off valve 18, giving priority to the needs of users of instrument compressed air.

[0042] In some embodiments, first isolation valves 23 are respectively provided on both sides of the first air transmission header pipe 21 at the connection with the first connecting pipe 16.

[0043] In some embodiments, second isolation valves 24 are respectively provided on both sides of the second air transmission header pipe 22 at the connection with the second connecting pipe 17.

[0044] In some embodiments, the first air transmission header pipe 21 is connected to each instrument compressed air distribution system 30 through a first branch pipe 25; third isolation valves 26 are respectively provided on both sides of the first air transmission header pipe 21 at the connection with the first branch pipe 25 .

[0045] In some embodiments, the second air transmission header pipe 22 is connected to each service compressed air distribution system 40 through a second branch pipe 27, and fourth isolation valves 28 are respectively provided on both sides of the second air transmission header pipe 22 at the connection with the second branch pipe 27 .

[0046] Preferably, the first isolation valve 23, the second isolation valve 24, the third isolation valve 26 and the fourth isolation valve 28 can be ball valves or solenoid valves.

[0047] It is understandable that dual isolation valves are arranged respectively before and after the branch pipes leading to different units, which can effectively ensure the segmented maintenance of the air supply network and isolation valves, with only one affected nuclear power unit.

[0048] In some embodiments, each instrument compressed air distribution system 30 includes a first pipeline 31, and a first compressed air tank 32 is provided on the first pipeline 31; one end of the first pipeline 31 is connected to the first branch pipe 25, and the other end of the first pipeline 31 is connected to air-consuming equipment of a nuclear island user.

[0049] In some embodiments, each instrument compressed air distribution system 30 includes a second pipeline 33, and at least two second compressed air tanks 34 connected in parallel are provided on the second pipeline 33. One end of the second pipeline 33 is connected to the first branch pipe 25, and the other end of the second pipeline 33 is connected to air-consuming equipment of a conventional island user.

[0050] In some embodiments, a control valve 35 is provided on the second pipeline 33 between the connection point of the first pipeline 31 and the first branch pipe 25 and the second air pressure tank 34, to control the connection and disconnection of the first pipeline 31 and the second pipeline 33. The control valve 35 can be automatically cut off when the pressure of the compressed air is lower than 0.58 MPa.

[0051] In some embodiments, each instrument compressed air distribution system 30 includes a third pipeline 36, one end of the third pipeline 36 is connected to the downstream of the second compressed air tank 34, and the other end of the third pipeline 36 is connected to air-consuming equipment of other users.

[0052] In some embodiments, the service compressed air distribution system 40 includes a fourth pipeline 41, and at least one third compressed air tank 42 is provided on the fourth pipeline 41; one end of the fourth pipeline 41 is connected to the second branch pipe 27, and the other end of the fourth pipeline 41 is connected to air-consuming equipment of conventional island users.

[0053] Preferably, the service compressed air distribution system 40 includes a fifth pipeline 43, one end of the fifth pipeline 43 is connected to the upstream of the third compressed air tank 42, and the other end of the fifth pipeline 43 is connected to air-consuming equipment of a nuclear island user.

[0054] Preferably, the service compressed air distribution system 40 includes a sixth pipeline 44, one end of the sixth pipeline 44 is connected to the downstream of the third compressed air tank 42 , and the other end of the sixth pipeline 44 is connected to air-consuming equipment of other users.

[0055] Preferably, a row of power busbar is configured for every two main air compressors 11 and the corresponding two dryers 12.

[0056] Preferably, a single compressed air station 10 is equipped with two rows of cooling water pipelines.

[0057] It can be understood that each compressed air station 10 introduces two rows of power supply busbars to ensure that when one row busbar is under maintenance, the capacity of the remaining air compressor units can meet the normal operating air consumption of two nuclear power units. The two closed cooling water systems from different nuclear power units or self-contained cooling water circulation devices have a dual power switching system to ensure the normal functioning of the cooling water system.

[0058] Preferably, N=2, 4 or 6; When N=2, that is, the number of the nuclear power units is two, the number of the compressed air station 10 is one, that is, one compressed air station 10 provides the required compressed air for the two nuclear power units; When N=4 or 6, the number of the compressed air stations (10) is two. That is, the number of the nuclear power units is 4 or 6, and the two compressed air stations 10 provide the required compressed air to the 4 or 6 nuclear power units.

[0059] In some embodiments, a temperature meter for detecting temperature can be provided on the pipeline within the air transmission network 20. Preferably, a pressure gauge for detecting air pressure can be provided on the pipeline within the air transmission network 20. Preferably, a dew point meter can be provided on the pipeline within the air transmission network 20.

[0060] The number and location of the temperature meter, pressure gauge, and dew point meter can be selected according to actual needs and are not specifically limited here.

[0061] In some embodiments, a check valve can be provided on the pipeline within the air transmission network 20 to prevent backflow of compressed air. The number and location of the check valves can be selected according to actual needs and are not specifically limited here.

[0062] As shown in FIG. 4, in some embodiments, at least three pressure sensors 50 are provided on the first connecting pipe 16, wherein at least two of the pressure sensors 50 are configured to trigger the start-up of at least one of the standby main air compressor 11 and the standby dryer 12 when the pressure value is lower than a first set value (such as 0.76 MPa), and at least two of the pressure sensors 50 are configured to trigger the unloading of one of the main air compressor 11 and the dryer 12 when the pressure value is higher than a second set value (such as 0.9 MPa). The time interval for generating the next trigger action can adopt the default value or be set by the user.

[0063] It can be seen that the pressure sensor 50 provided on the outlet pipe of the compressed air dry tank controls the operation of the main air compressor 11 and the dryer 12 through signals, which is conducive to realizing intelligent control of the air compressor station.

[0064] This solution proposes a compressed air supply system for multi-unit nuclear power plants from the perspective of overall planning and phased implementation of nuclear power plants. It mainly includes: eliminating the emergency air compressor, dryer and front and rear compressed air tanks installed in the nuclear island. The first phase and second phase of the project will each construct a main air compressor station in stages and connect to network to supply air. The air supply quality will meet instrument air requirements in a single step and also meet the service compressed air quality requirements. The total capacity of the air compressors configured in each main air compressor station meet the air consumption for the operation and maintenance of two nuclear power units, with at least two standby air compressors available, and four air compressors and dryers are generally configured. The total capacity of the air compressors configured in the two air compressor stations needs to be calculated to meet the air consumption for the operation and maintenance of six nuclear power units, with at least two standby air compressors available. Each main air compressor station introduces two rows of power supply busbars to ensure that when one row busbar is under maintenance, the capacity of the remaining air compressor units can meet the normal operating air consumption of two nuclear power units. The two closed cooling water systems from different nuclear power units or self-contained cooling water circulation devices have a dual power switching system to ensure the normal functioning of the cooling water system. The instrument compressed air and the service compressed air for plants are each drawn out from the main air compressor station. The head and tail ends of the plant distribution header pipe are connected to two main air compressor stations respectively. During phased construction, the dotted pipe section in FIG. 3 can be removed after the corresponding plant header pipes and isolation valves of units 5 and 6 are installed and cleaned. Dual isolation valves are arranged respectively before and after the branch pipes leading to different units, which can effectively ensure the segmented maintenance of the air supply network and valves, with only one affected nuclear power unit. An automatic isolation valve is arranged on the compressed air header pipe in the main air compressor station to automatically cut off the supply of plant compressed air when the pressure is low, giving priority to the needs of users of instrument compressed air.

[0065] It can be understood that the compressed air supply system for multi-unit nuclear power plants, on the basis of meeting the reliability requirements of downstream users for the compressed air supply system, reasonably reduces equipment configuration and cost. The standby air compressors and dryers in the plant are fully shared through networking, and the power supply and water source of the air compressor unit are reasonably designed, which can effectively meet the compressed air required for normal operation of other units during busbar maintenance, and create conditions for online maintenance of plant pipelines and valves, thereby improving the availability of the units. By rationally designing multiple automatic controls and barrier measures for system pressure, the needs of users of instrument compressed air, especially those for nuclear island instruments, can be effectively guaranteed, thereby ensuring stable and safe operation of the unit.

[0066] The technical solution of the present invention has a great cost advantage in a six-unit nuclear power plant with eight air compressors and dryers compared to 21 in Solution 1 and 18 in Solution 2.

[0067] It can be understood that the above embodiments only express the preferred implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A compressed air supply system for a multi-unit nuclear power plant, comprising at most two compressed air stations (10) connected to N nuclear power units through an air transmission network (20), each of the compressed air stations (10) comprises four main air compressors (11) connected in parallel and four dryers (12) correspondingly connected to the four main air compressors (11), and the four dryers (12) are arranged in parallel.

2. The compressed air supply system for a multi-unit nuclear power plant according to claim 1, wherein two compressed air wet tanks (13) arranged in parallel are configured between the four main air compressors (11) and the four dryers (12).

3. The compressed air supply system for a multi-unit nuclear power plant according to claim 2, wherein two compressed air dry tanks (14) arranged in parallel are configured between the air transmission ends of the four dryers (12) and the air transmission network (20).

4. The compressed air supply system for a multi-unit nuclear power plant according to claim 3, wherein the air transmission ends of the two compressed air dry tanks (14) of each compressed air station (10) are connected to an air transmission main pipe (15); wherein, the air transmission network (20) comprises a first air transmission header pipe (21) and a second air transmission header pipe (22), the first air transmission header pipe (21) is respectively connected to the air transmission main pipes (15) of all the compressed air stations (10) and instrument compressed air distribution systems (30) of all the nuclear power units; wherein, the second air transmission header pipe (22) is respectively connected to the air transmission main pipes (15) of all the compressed air stations (10) and the same nuclear power first air transmission parent pipe (21) is respectively connected to the air transmission main pipe (15) and service compressed air distribution systems (40) of all the nuclear power units.

5. The compressed air supply system for a multi-unit nuclear power plant according to claim 4, wherein the first air transmission header pipe (21) is connected to the air transmission main pipe (15) through a first connecting pipe (16); and the second air transmission header pipe (22) is connected to the air transmission main pipe (15) through a second connecting pipe (17).

6. The compressed air supply system for a multi-unit nuclear power plant according to claim 5, wherein an automatic shut-off valve (18) is provided between the air transmission main pipe (15) and the second connecting pipe (17).

7. The compressed air supply system for a multi-unit nuclear power plant according to claim 5, wherein first isolation valves (23) are respectively provided on both sides of the first air transmission header pipe (21) at the connection with the first connecting pipe (16).

8. The compressed air supply system for a multi-unit nuclear power plant according to claim 5, wherein second isolation valves (24) are respectively provided on both sides of the second air transmission header pipe (22) at the connection with the second connecting pipe (17).

9. The compressed air supply system for a multi-unit nuclear power plant according to claim 8, wherein the first air transmission header pipe (21) is connected to each of the instrument compressed air distribution systems (30) through a first branch pipe (25); wherein, third isolation valves (26) are respectively provided on both sides of the first air transmission header pipe (21) at the connection with the first branch pipe (25).

10. The compressed air supply system for a multi-unit nuclear power plant according to claim 9, wherein the second air transmission header pipe (22) is connected to each of the service compressed air distribution systems (40) through a second branch pipe (27); wherein, fourth isolation valves (28) are respectively provided on both sides of the second air transmission header pipe (22) at the connection with the second branch pipe (27).

11. The compressed air supply system for a multi-unit nuclear power plant according to claim 10, wherein each of the instrument compressed air distribution systems (30) comprises a first pipeline (31), and a first compressed air tank (32) is provided on the first pipeline (31); wherein, one end of the first pipeline (31) is connected to the first branch pipe (25), and the other end of the first pipeline (31) is connected to air-consuming equipment of a nuclear island user.

12. The compressed air supply system for a multi-unit nuclear power plant according to claim 11, wherein each of the instrument compressed air distribution systems (30) comprises a second pipeline (33), and at least two second compressed air tanks (34) connected in parallel are provided on the second pipeline (33); wherein, one end of the second pipeline (33) is connected to the first branch pipe (25), and the other end of the second pipeline (33) is connected to air-consuming equipment of a conventional island user.

13. The compressed air supply system for a multi-unit nuclear power plant according to claim 12, wherein a control valve (35) is provided on the second pipeline (33) between the connection point of the first pipeline (31) and the first branch pipe (25) and the second compressed air tank (34).

14. The compressed air supply system for a multi-unit nuclear power plant according to claim 13, wherein each of the instrument compressed air distribution systems (30) comprises a third pipeline (36), one end of the third pipeline (36) is connected to the downstream of the second compressed air tank (34), and the other end of the third pipeline (36) is connected to air-consuming equipment of other users.

15. The compressed air supply system for a multi-unit nuclear power plant according to claim 14, wherein each of the service compressed air distribution systems (40) comprises a fourth pipeline (41), and a third compressed air tank (42) is provided on the fourth pipeline (41); wherein, one end of the fourth pipeline (41) is connected to the second branch pipe (27), and the other end of the fourth pipeline (41) is connected to air-consuming equipment of a conventional island user.

16. The compressed air supply system for a multi-unit nuclear power plant according to claim 15, wherein each of the service compressed air distribution systems (40) comprises a fifth pipeline (43), one end of the fifth pipeline (43) is connected to the upstream of the third compressed air tank (42), and the other end of the fifth pipeline (43) is connected to air-consuming equipment of a nuclear island user.

17. The compressed air supply system for a multi-unit nuclear power plant according to claim 15, wherein each of the service compressed air distribution systems (40) comprises a sixth pipeline (44), one end of the sixth pipeline (44) is connected to the downstream of the third compressed air tank (42), and the other end of the sixth pipeline (44) is connected to air-consuming equipment of other users.

18. The compressed air supply system for a multi-unit nuclear power plant according to any one of claims 1 to 17, wherein a row of power busbar is configured for every two main air compressors (11) and the corresponding two dryers (12).

19. The compressed air supply system for a multi-unit nuclear power plant according to any one of claims 1 to 17, wherein a single compressed air station (10) is equipped with two rows of cooling water pipelines.

20. The compressed air supply system for a multi-unit nuclear power plant according to any one of claims 1 to 17, wherein N = 2, 4 or 6; when N=2, the number of the compressed air station (10) is one; when N=4 or 6, the number of the compressed air stations (10) is two.

21. The compressed air supply system for a multi-unit nuclear power plant according to any one of claims 5 to 17, wherein at least three pressure sensors (50) are provided on the first connecting pipe (16), wherein at least two of the pressure sensors (50) are configured to trigger the start-up of at least one of the standby main air compressor (11) and the standby dryer (12) when the pressure value is lower than a first set value, and at least two of the pressure sensors (50) are configured to trigger the unloading of one of the main air compressor (11) and the dryer (12) when the pressure value is higher than a second set value.

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