KR20030007441A - System and method for cooling transformers - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling system and method of a transformer for cooling an insulating fluid flowing through a transformer using a fluid in an air heat exchanger. There are a number of vertical cooling tubes in communication, these tubes forming vertical air passages, which use natural convection and endothermic phenomena to cool the fluid.

Description

System and method for cooling transformers

The power transmission industry uses a variety of power supply transformers, such as stepping up voltages in large-capacity power plants with continuous power transmission, and small-capacity distribution transformers stepping down the voltage to supply residential and industrial complexes. The transformer is used at the installation. The transformer can have a rated power of thousands of volts and can dissipate a lot of heat during operation. If this heat is not properly dissipated, it can damage the transformer, reducing its useful life or even making it inoperable. Most high-capacity power transformers are immersed in insulating fluid to insulate and cool the components. Typical insulating insulating fluids include standard mineral oils, high temperature mineral oils and high temperature synthetic fluids.

During operation, the transformer can be sufficiently cooled by the ONAN of the insulating fluid or oil in the transformer and the air surrounding the transformer. Using naturally circulating oils and air, the fluid circulates through the core of the transformer and through an external heat exchanger or cooler by natural tropical flow phenomena. The cooler on the outside of the transformer is intended to allow natural convection of air. Typically, large convection heat exchangers are needed because natural convection is relatively inefficient.

In order to overcome the limitations of the above-mentioned type (ONAN) type of cooling, a system of natural circulation oil and forced circulation air (ONAF) is used. The insulating fluid circulates through the transformer core and external cooler for natural tropical flow. The heat exchanger or cooler outside the transformer is adapted to receive a fan that pushes air over the cooler. This improves the cooling performance of the heat exchanger, thereby reducing the number of heat exchangers required to achieve the same cooling performance. It can also reduce the overall size of the combination of transformer and cooler.

To increase the heat capacity even further, forced oil and air (OFAF) coolers are used. The oil is forced to pass through the transformer using a pump. Increasing the fluid velocity in the transformer allows for greater heat transfer between the material of the heat exchanger and the fluid. Forced air and oil are forced through the heat exchanger to increase the cooling efficiency of the heat exchanger.

Radiators are the most common heat exchangers used to cool insulating fluid in a transformer. Radiators take various shapes and structures. One type of cooler is a tubular radiator with a carbon steel tube welded to a pipe header. Another common type of cooler consists of carbon steel panels stacked to form a radiator unit. These radiators are used in banks consisting of a number of individual radiator sections and can be screwed directly to the sides of the transformer. During operation, insulating fluid flows from the transformer to the carbon steel panel by injecting it into the top of the radiator and exiting the bottom. To cool, air flows vertically across the radiator panel to take heat away from the fluid. As mentioned above, natural convection of air is insufficient to achieve the desired cooling performance. Therefore, the fan is mounted so that air easily flows across the radiator panel for improving the cooling performance. Typically, however, the fan is installed so that air flows horizontally across the panel, thus failing to take advantage of the natural heat flow of the ambient atmosphere. In addition, current radiator technology requires large space to cool insulating fluids. The individual radiator panels become more inefficient as the amount of cooling required increases.

Panel-type radiators are made entirely of thin film material and have welded seams around each panel. These joints are the points of preferential corrosion, and this structure needs to be kept in mind. Moreover, carbon steel and other materials used in the structure of radiators have a relatively low thermal conductivity.

Since the radiator is filled with insulating fluid, the amount of insulating fluid increases with increasing number and size of radiators. As will be appreciated by those skilled in the art, this not only increases the cost of the transformer but also increases the weight and affects the center of gravity of the transformer to meet the structural robustness of the tank of the transformer.

In the ONAF type, the cooling system uses a small fan to minimize the stress on the radiator. Small fans do not carry large amounts of air, so if a structure requires a significant amount of cooling air, a large number of fans are needed. Using many fans introduces additional wiring and other problems of the cooling system, such as insufficient air distribution, increased maintenance costs, and electrical losses.

When the radiator operates under natural fluid flow, the flow of fluid occurs because of the relative density difference between hot and cold oils, as described above. As with any fluid system, this system follows a curve plot of flow versus resistance, with the flow of fluid decreasing as the resistance or pressure drop in the system increases. If a single radiator is considered, the outermost panel (far from the tank) assumes that the oil flows longer as it travels longer and encounters greater resistance to reach the outer panel. Therefore, the process of cooling the oil is not maximized and the cooling of the insulating fluid is insufficient.

While various systems have been described in the prior art to cool insulating fluid flowing through a transformer, there has been a need for a heat transfer device that cools insulating fluid that is more efficient, smaller and lighter than conventional cooling devices for transformers. The present invention overcomes the disadvantages of the prior art, while meeting these and other needs.

TECHNICAL FIELD The present invention generally relates to the field of cooling a transformer (tansformer), and more particularly to an insulating fluid cooler for a transformer using a fluid in an air heat exchanger.

1 is a perspective view of a preferred transformer cooling system located in an electrical transformer;

FIG. 2 is a side view of the preferred cooling system for transformers of FIG. 1 located in a schematic illustrated electrical transformer; FIG.

3 is a partially enlarged side view of the present invention along line 3-3 in the direction of the arrow shown in FIG. 2;

Figure 4 is an enlarged cross-sectional view of the cooling tube of the present invention along the line 4-4 in the direction of the arrow shown in Figure 3,

5 is a side view of the preferred trans cooling system of FIG. 2 in which a portion of the electrical transformer is cut away while further illustrating the flow of insulating fluid and air during operation of the present invention.

As described throughout, there is provided a cooling system for cooling an insulating insulating fluid flowing through a transformer, the system having one or more cooling tubes oriented to have an upper opening and a lower opening. Each tube has a plurality of radially protruding inner fins and a plurality of outer fins extending longitudinally. In addition, these tubes are interconnected along the longitudinal axis by the connection of the outer fins so as to form a tubular bundle. One or more distribution headers are provided for fluid communication between the transformer and the upper opening of the cooling tube. Additionally, one or more collecting headers are provided to allow fluid to communicate between the transformer and the lower opening of the cooling tube. Finally, a plurality of vertical air channels are formed by the tubular outer fins.

In another aspect of the present invention, there is provided a method for cooling an insulating insulating fluid flowing through a transformer, wherein the insulating insulating fluid is circulated from the transformer through one or more vertical tubes, and the airflow is insulated insulating. It is circulated through a vertical air channel formed by the interconnection of the tubes to cool the fluid.

Systems and methods are provided for cooling a transformer with fluid in an air heat exchanger to cool the insulating fluid flowing through the present transformer. The system includes a plurality of aluminum cooling tubes in fluid communication with the transformer to cool the insulating fluid. These tubes are designed to create a vertical air stream to cool the fluid using the natural convective air flow back to the system.

The above objects and advantages of the present invention will be more readily understood from the following detailed description with reference to the accompanying drawings of preferred embodiments according to the present invention.

With reference to the detailed accompanying drawings and preferentially with reference to FIGS. 1 and 2, the cooling system of the present invention is indicated generally by the reference numeral 10. The cooling system 10 is adapted to cool the insulating insulating fluid used to thermally and electrically insulate the windings and other internal components of the electrical transformer using fluid in the air heat exchanger. In a preferred embodiment, the cooling system 10 consists of a plurality of cooling tubes 12 which communicate fluid to an electrical transformer 14 via one or more distribution headers 16 and an aggregation header 18. The distribution header 16 connects the upper vertical part of the transformer 14 to the upper part of the cooling tube 12. The gathering header 18 symmetrically identical to the distribution header 16 connects the lower vertical part of the transformer 14 to the lower part of the cooling tube 12. It will be appreciated that a number of hardware configurations may connect the cooling tube 12 to the transformer 14, which is included within the technical scope of the present invention.

3 is a partial side view of the cooling system 10 along line 3-3 in the direction of the arrow shown in FIG. Referring to Figures 1, 2 and 3, in a preferred embodiment each dispensing header 16 has a manifold 20 for communicating fluid to the transformer. One or more wing-shaped extensions 22 communicate fluid to the manifold 20 and extend outwardly therefrom. The bottom surface of each wing-shaped extension 22 has a number of openings or holes (not shown) that connect to the top of the cooling tube 12 and communicate fluids so as to be completely connected to the transformer 14. Let's do it. The gathering header 18 is symmetrically identical to the distribution header 16 and consists of an extension 26 which is wing-shaped corresponding to the manifold 24 which communicates fluid to the bottom of the cooling tube 12.

As described above, the cooling system includes a plurality of cooling tubes 12 that communicate fluid to the transformer. FIG. 4 is an enlarged cross-sectional view of the cooling tube 12 along lines 4-4 shown in FIG. 3, which cooling tube 12 is preferably round and made of injection molded aluminum. Aluminum has good thermal conductivity, light weight, and excellent corrosion resistance. It will be appreciated that any material having these characteristics may be included within the technical scope of the present invention. As described in more detail below, each cooling tube 12 has a plurality of cooling tubes (12) in such a way that it has a vertical fluid channel 28 and forms a vertical air channel 30 in a honeycomb shape. 12) with a plurality of spaced outer pins to allow them to be connected to each other. Preferably, each cooling tube 12 has a wall 32, a radially extending inner fin 34 spaced apart circumferentially, and an outer cooling fin 36 spaced apart circumferentially. Radially extended nipper pins 38 spaced in thirds, and radially extended ball pins 40 alternately spaced between the external cooling fins 36 and circumferentially spaced. All fins extend longitudinally along the surface of the wall 32 of the cooling tube 12.

Six inner fins 34 extend from the inner surface of the cooling tube wall 32 and are evenly spaced around the inner circumference of the cooling tube wall 32. The inner fin 34 extends radially inward toward the center of the cooling tube 12 in a length of about 1/2 of the radius of the cooling tube. These internal fins 34 help absorb heat from the insulating fluid flowing through the cooling tube 12.

The twelve outer fins 36, 38, 40 extend longitudinally along the outer surface of the cooling tube wall 32, and radially outward from the cooling tube wall 32 in a length approximately the diameter of the cooling tube 12. Stretches. In addition, all of the inner and outer fins 34, 36, 38, 40 have longitudinal grooves or channels along the surface of the fins, which create additional surface area through the interior of the cooling tube 12 It makes it possible to cool the flowing insulating fluid further.

The external forceps pin 38 and the external ball pin 40 are connected to the cooling tube wall 32 and are evenly spaced around the circumference of the cooling tube wall 32 alternately between the external cooling fins 36. Three external force pins 38 and three external ball pins 40 are positioned along the cooling tube wall 32 in the same manner as in FIG. 4 showing the cooling tube 12 in cross-section. As the outer fins 38 and 40 penetrate through the cooling tube wall 32 from the inside, the outer fins 38 and 40 are continuous with the six inner fins 34. In addition, the arrangement of the fins as it moves clockwise around the cooling tube wall 32 places the forceps pin 38 after the cooling fins 36, followed by another cooling fin 36. ) And then the ball pin 40. The tong pin 38 and the ball pin 40 are provided with the tongs 42 and the ball 44, respectively, and the ends thereof are attached to each other. The tong pin 38 and the ball pin 40 fit together with the forceps 42 and the ball 44 so that a plurality of tubes 12 make a structure or tube bundle 46 fastened to each other in a honeycomb shape for the cooling system. It can be connected.

The tube bundle 46 formed by connecting the cooling tubes 12 to each other forms a vertical air channel or a passage 30. The air channel 30 extends along the entire outer surface of the cooling tube fins 36, 38, and 40 to move the air vertically in the lower portion of the cooling system 10 using natural convection and endothermic phenomenon. do. The endothermic phenomenon or "chimney effect" occurs when the air drawn up within the confined space created by the cooling tube and its associated external fins expands rapidly in the vertical direction. If the air expands rapidly in the vertical direction upwards, the velocity of the air flows faster, resulting in better heat transfer. Therefore, the chimney effect takes advantage of the natural characteristics of the airflow to increase the cooling of the insulating fluid. It will be appreciated that other forms of cooling tube 12 that use an endothermic phenomenon of air to cool the insulating fluid are within the technical scope of the present invention.

FIG. 5 is a schematic diagram of the cooling system of FIG. 2 and a transformer coupled thereto, further illustrating the flow of insulating fluid and air of the present invention. During operation, heat generated by the transformer 14 causes the insulating fluid 48 surrounding the core 50 of the transformer to convection into the top of the transformer compartment 52 and into the distribution header 16. The manifold 20 in the distribution header 16 receives the fluid 48, and as the fluid begins to cool, it descends along individual cooling tubes 12 past the wing-shaped extensions 22. The insulating fluid 48 rapidly cools in the cooling tube 12 and descends into the extensions 26 which are wing shaped in the gathering header 18. The fluid 48 then flows into the manifold 24 of the gathering header 18 and then into the transformer compartment 52 where it is heated and circulation starts again. It will be appreciated that various fluids may be used, such as insulating fluids including mineral oils and high temperature synthetic fluids.

During the cooling process, the atmosphere is sucked into the cooling system 10 along the direction shown by arrow 54, first being slightly warmed by the gathering header 18 at the bottom of the cooling system 10. Next, the air flows up through the vertical air channel 30, where it is heated, expands and speeds up. Finally, the air flows up through the distribution header 16 and exits the cooling system 10 to send heat from the insulating fluid 48 to the atmosphere along the direction shown by arrow 56 with this air. As mentioned above, the natural convection of the vertical airflow makes it possible to cool the insulating fluid more efficiently. It will be appreciated that other methods of flowing air vertically through the cooling system are within the technical scope of the present invention.

In a conventional heat exchanger or cooling system for transformers, forced air and forced fluid and combinations thereof can be used to further cool the insulating fluid. In the form of natural circulation oil and forced circulation air (ONAF), the fan 58 (see FIGS. 2 and 3 and 5) is connected to the bottom of the tube bundle 46, which is perpendicular to the cooling tube 12. This increases the airflow and cools the insulating fluid further.

In addition, cooling can be achieved by using forms of forced circulation oil and natural circulation air (OFAN). A pump (not shown) is mounted inside the transformer to increase the flow of fluid through the cooling tube 12 across the core 50. This also has the effect of increasing the cooling of the insulating fluid. The combination of forced oil and forced air (OFAF) provides much better cooling characteristics of the cooling system.

The cooling system constructed and operated as described above uses a number of vertical aluminum cooling tubes to remove heat from the insulating fluid used in the electrical transformer. In a preferred form, the connected tubes form a vertical air channel, which utilizes natural convection and endothermic phenomena to cool the insulating fluid flowing through the cooling tube. The use of endothermic phenomenon further increases the cooling of the fluid by taking advantage of the natural thermal properties of the air flowing through the cooling system. Therefore, in an environment where greater cooling is achieved in a conventional radiator by mounting a fan that forces air to circulate across the radiator horizontally, the conventional radiator can be reduced or completely eliminated in the cooling system of the present invention. It can achieve the same cooling level shown in the structure.

Because of the high efficiency cooling realized with the present invention, a small number of cooling tubes are needed to cool the transformer. The smaller number of cooling tubes allows the use of fluid in air heat exchangers that are significantly smaller and lighter than in conventional trans radiator structures. In a trans structure, especially for trans used in areas with limited space, such as in urban areas with limited land areas for installing trans substations, size is very important. In addition, smaller cooling systems reduce mechanical stress on the transformer. In addition, the reduced number of tubes reduces the amount of insulating fluid that cools the transformer.

Another advantage of the present invention is that the cooling tube is made of aluminum. This reduces the weight of the radiator cooling system and prevents excessive stress on the trans structure. In addition, aluminum has better thermal conductivity than carbon steel used in conventional trans radiator structures.

The welded joint of the transformer radiator is the main point of corrosion. The cooling system formed as described above uses about 15% of the welded joints used in conventional trans radiators, thus reducing the possibility of weakening the cooling system structure.

According to the foregoing, the present invention has been greatly improved to achieve all the objectives described herein with the other advantages of the original structure.

It will be fully understood that any form and additional combinations may be used, and other forms and additional combinations may be used without particular mention. This is considered within the scope of the claims.

Claims (21)

A plurality of cooling tubes each having a substantially vertical orientation, each having an upper opening and a lower opening and interconnected to form a tubular bundle; One or more dispensing headers positioned to communicate fluid between the transformer and the upper opening of the cooling tube; At least one collecting header positioned to communicate fluid between the transformer and the lower opening of the cooling tube; And a plurality of vertical air channels formed into interconnected tubular bundles. The cooling system of claim 1, wherein the cooling tube further comprises a plurality of radially outwardly projecting outer fins extending longitudinally along the outer surface of the tube. 3. The cooling system of claim 2, wherein the cooling tube further comprises a plurality of radially inwardly projecting inner fins extending longitudinally along the inner surface of the tube. 4. The cooling system of claim 3, wherein the fins have a longitudinal groove extending parallel to the tube. The cooling system of claim 3, wherein the inner fins and the outer fins are spaced at equal intervals. 3. The cooling system of claim 2, wherein the outer pin has a plurality of outer pins protruding radially outward from an outer surface of the tube, each pin having a pin at its end. 7. The cooling system of claim 6, wherein the outer pin has a plurality of outer ball pins projecting radially outwardly from an outer surface of the tube, each outer ball pin having a ball portion at its end. 8. The cooling system of claim 7, wherein the forceps pins and ball pins are capable of interconnecting them to form a tubular bundle shape. 3. The cooling system of claim 2, wherein the outer fins have a plurality of outer cooling fins protruding radially outward from the outer surface of the tube. The cooling system of claim 1, wherein the cooling tube is made of aluminum. 2. The apparatus of claim 1, wherein each of the one or more dispensing headers comprises a manifold for communicating fluid to the transformer and one or more wing-shaped extensions extending therefrom, the one or more wing-shaped extensions respectively. Cooling system having a lower surface with an opening of. 12. The cooling system of claim 11, wherein each opening of said wing-shaped extension allows fluid to communicate with an upper opening of a corresponding cooling tube. The apparatus of claim 1, wherein each of the one or more gathering headers includes a manifold for communicating fluids to the transformer, and one or more wing-shaped extensions extending therefrom, the one or more wing-shaped extensions respectively. Cooling system having an upper surface with an opening. 14. The cooling system of claim 13, wherein each opening of said wing-shaped extension allows fluid to communicate with a lower opening of a corresponding cooling tube. The cooling system of claim 1, wherein the cooling tubes of the tube bundle are connected in a honeycomb arrangement. Circulating the insulating insulating fluid down from the transformer through one or more vertical tubes; And circulating the airflow upwards through a vertical air channel formed by the interconnection of the tubes to cool the insulating insulating fluid. 17. The method of claim 16 wherein the step of circulating the airflow through the vertical air channel occurs through natural tropical flow phenomena. 17. The method of claim 16 wherein the step of circulating the airflow through the vertical air channel occurs through an endothermic phenomenon. 17. The method of claim 16 wherein the step of circulating the airflow through the vertical air channel occurs through a forced air stream. 17. The method of claim 16 wherein the step of circulating the insulating insulating fluid occurs through natural tropical flow phenomena. 17. The method of claim 16 wherein the step of circulating the insulating insulating fluid occurs through an insulating insulating fluid flow that is forced to circulate.