Non-immersed transformer

Abstract

A non-immersion transformer is provided. The transformer includes a magnetic core and a coil winding that forms a plurality of winding turns around the magnetic core, a cooling system, and a first conductive connector. The cooling system includes a cooling tube for the flow of a cooling fluid, the cooling tube extending along the coil winding and including a first portion adjacent to a turn of the coil winding and a second portion adjacent to another turn of the coil winding. The conductive connector is arranged at one of the first portion and the second portion to electrically connect the inside of the cooling tube to the turn of the coil winding.

Description

Technical Field

[0001] The present disclosure relates to transformers, and more particularly, to non - immersed transformers including a fluid cooling system. Background Art

[0002] To cool down a transformer, some systems use a gas (such as air) to refrigerate its windings or coils. This air cooling can be forced or natural. In the case of forced air cooling, blowing equipment (such as fans) can be positioned to blow an air stream onto the windings. However, the cooling capacity of such an air stream may be insufficient to dissipate heat.

[0003] It is also known to use water coolers to refrigerate non - immersed transformers, which includes passing forced air through tubes having a cold fluid (such as water) circulating therein to facilitate refrigerating the air stream, and then directing such a cold air stream to the coils of the transformer to improve its cooling capacity. This solution presents several drawbacks, such as the necessity to use a housing, thereby increasing the footprint and cost of the transformer.

[0004] Alternative solutions include using hollow conductors or metal tubes (such as made of copper or aluminum) as the conductive turns of the windings of the transformer and also for the circulation of the cooling fluid. The use of these metal tubes involves several drawbacks: such hollow conductor tubes require additional space to accommodate the conduits, that is, to allow sufficient flow of the cooling fluid, and thus, not only the size of the coil windings but also the size of the entire transformer, that is, the footprint, increases significantly. In addition, such special wound tubes are difficult to manufacture and expensive. Moreover, the relatively large size of these hollow conductors results in a significant increase in additional losses in the conductors due to eddy currents.

[0005] Another alternative is to use cooling tubes around or inside the transformer coil windings, which have a dielectric fluid (such as oil, natural ester or synthetic ester fluid) circulating therein. K3 fluids, that is, dielectric fluids with a flash point above 300 °C, can also be used, but they are flammable fluids. Additionally, some dielectric fluids may be harmful to the environment in case of leakage or fire outbreak.

[0006] On the other hand, the use of non - dielectric fluids involves other drawbacks or technical difficulties due to the presence of an electric field and the risk of discharge or other electrical phenomena inside the transformer.

[0007] In summary, it is desirable to provide an environmentally friendly cooling solution for non - immersed transformers, with high cooling capacity and which is safe in operation / reduces the risk of transformer failure and / or malfunction, while being cost - effective. Summary of the Invention

[0008] A non-immersion transformer is provided. The transformer includes a magnetic core and a coil winding that forms a plurality of winding turns around the magnetic core, a cooling system, and a first conductive connector. The cooling system includes a cooling tube for a cooling fluid flow that extends along the coil winding, and wherein the cooling tube includes a first portion adjacent to a turn of the coil winding and a second portion adjacent to another turn of the coil winding. The first conductive connector is arranged at one of the first portion and the second portion to electrically connect the inner side of the cooling tube to the turn of the coil winding.

[0009] Electrically connecting the inner side of the cooling tube to the coil winding allows for equalizing the voltage of the cooling fluid circulating inside the cooling tube and the voltage of the turn of the coil winding to which the conductive connector is connected. Since the cooling fluid will be in contact with the inner side of the cooling tube, the cooling fluid will be electrically connected to the coil winding. That is, at the first portion or the second portion, the voltage of the cooling fluid will be the same as the voltage of the turn of the coil winding to which it is electrically connected and approximate to the voltage of the surrounding turns, and thus the voltage difference in these regions will be negligible.

[0010] This enables the cooling system to work with a non-dielectric cooling fluid such as water, because even when using a conductive fluid, the conductive connector can thus substantially prevent the generation of a large electric field (e.g., an electric field greater than 1 kV / mm), which may cause dielectric problems such as partial discharge or direct flashover inside the transformer. Partial discharge can seriously affect the function of the transformer and can also damage the insulation, leading to premature dielectric aging of the insulation, which will result in a failure. Direct flashover may occur if the insulation can no longer withstand a large electric field.

[0011] In addition, the absence of a large voltage difference along the cooling tube prevents current from appearing in the cooling fluid and thus avoids several problems such as heating of the cooling fluid, electrolysis, ion and / or gas generation.

[0012] Therefore, the cooling system can use water (e.g., distilled and / or deionized water) as the cooling fluid, which enables a cost-effective and environmentally friendly solution using a non-flammable cooling fluid or coolant, thus preventing the risk of fire outbreak and achieving a safe transformer in operation.

[0013] In an example, the first portion of the cooling tube can be adjacent to an end of the coil winding, and the second portion can be adjacent to the other end of the coil winding, so as to equalize the voltage of the cooling fluid circulating inside the cooling tube and the voltage of the end of the winding (i.e., the portion of the winding that includes the first or last turn of the coil winding).

[0014] In an example, the transformer can further include a second conductive connector such that the first conductive connector can be arranged at the first portion and the second conductive connector can be arranged at the second portion.

[0015] By using two conductive connectors disposed at two turns of the winding, the voltage of the cooling fluid can be equalized with the voltage of each connected turn of the winding, which reduces the risk of generating a large electric field in these regions of the winding coil.

[0016] The use of the second conductive connector can depend on the electrical configuration of the transformer. For example, in the case where the end of the coil is grounded, such as in a three-phase transformer with a star connection and the neutral point grounded, for example, a single conductive connector disposed at the first position or the second position is sufficient. In a transformer with a star connection (where the neutral point is not grounded) or a delta connection transformer, two conductive connectors can be used.

[0017] In the example, the cooling fluid can be water which is environmentally friendly and not a flammable fluid, that is, the outbreak of fire is avoided.

[0018] In the example, the cooling tube can further include a plurality of windings to extend the path of the cooling fluid substantially between one end of the winding (i.e., substantially corresponding to or adjacent to the first or last coil winding turn) and one of the feed main pipe and the return main pipe.

[0019] By using a plurality of windings, the path of the cooling fluid can be increased, that is, the length traveled by the cooling fluid before reaching the start of the winding and / or after leaving the end of the winding is extended. The path can be determined, for example, as the loop completed by the fluid between the heat exchanger and the start and / or end of the winding. As the path length increases, the resistance of the cooling fluid also increases, which reduces the current that may be generated in the cooling fluid.

[0020] The combination of at least the first conductive connector and the cooling tube including a plurality of windings enhances the performance of the transformer. In the case of including the first conductive connector and the second conductive connector and using a plurality of windings, the function of the transformer is improved.

[0021] In the example, the transformer can be a high-voltage transformer, that is, generating voltages from 0.4 kV to up to 72 kV and rated powers from 50 kVA to 100 MVA. Description of the Drawings

[0022] Referring to the accompanying drawings, specific embodiments of the present device will be described below by way of non-limiting examples, in which:

[0023] Figure 1 A schematic simplified cross-section of a transformer including a magnetic core and a cooling system according to an example is shown; and

[0024] Figure 2 Is shown Figure 1Schematic enlarged view of a part of a transformer. Detailed implementation

[0025] Figure 1 Depicts a non - liquid - immersed or dry - type transformer 1, which includes a magnetic core 100, at least one coil winding 300 around the Y - axis, and a cooling system 200.

[0026] The coil winding 300 can form multiple turns (shown as striped lines) around the magnetic core 100: a first turn 301, which is the start of the winding; multiple intermediate turns 302, and a last turn 303, which is the end of the winding. Thus, the coil winding 300 can include two ends, namely the parts of the winding that respectively contain the first turn and the last turn of the coil winding.

[0027] The coil winding 300 can be made of a conductive material (such as copper or aluminum), and except for parts where it may be necessary to be close to the winding (such as in the ends for connecting cables to output the generated voltage), the conductive material can be covered or coated with an insulating dielectric material (such as polyester or epoxy resin).

[0028] Although a single - phase magnetic core is depicted in Figure 1 , in the example, the transformer 1 can be a three - phase magnetic core including three columns (each column at least including a coil winding according to any disclosed example). In such an example, the windings of the transformer can be connected in the form of a delta, zigzag, or star connection.

[0029] The coil winding 300 can have a coil cover or a cover made of an insulating material (such as epoxy resin) to protect the effective part of the transformer, that is, the winding turns. The cover can also include multiple input / output connections, such as for cooling tubes, for voltage bushings to output the generated voltage, etc.

[0030] Figure 1 The cooling system 200 is also shown, and the cooling system can include a heat exchanger 210, which connects a feed main pipe 230 for inputting cold water to the windings of the transformer and a return main pipe 240 for outputting the heated water from the windings of the transformer to the heat exchanger. In the example, the feed main pipe 230 and the return main pipe 240 can be made of a metal material and / or can be grounded.

[0031] The cooling system 200 may further include a cooling pipe 220, which may be made of a dielectric material and may be coupled to a supply main pipe 230 and a return main pipe 240 at coupling points 221 and 222 respectively at its two ends. The cooling pipe 220 may extend along the coil winding 300 and may form a loop around the axis Y, thereby reducing the floor area, i.e., the volume occupied by the cooling pipe. "Extending along the coil winding" means that the cooling pipe 220 (or its loop) may alternatively be arranged between adjacent or subsequent winding turns, around the coil winding, in the central vacant space inside the coil winding, or any combination thereof, such as partially around the coil and partially arranged between adjacent winding turns. By extending the cooling pipe 220 along the coil winding, the cooling capacity of the cooling system is improved because the heat generated at the winding can be dissipated more effectively due to the increased efficiency of the heat transfer solution.

[0032] The cooling pipe 220 may include a first portion 250 adjacent to a turn of the coil winding and a second portion 260 adjacent to another turn of the coil winding.

[0033] In an example (see Figure 1 ), the first portion 250 may be adjacent to an end of the coil winding (i.e., adjacent to the first turn), and the second portion 260 may be adjacent to the other end of the coil winding (i.e., adjacent to the last turn). In another example (not shown), the first portion 250 may be adjacent to the second turn of the coil winding, and the second portion 260 may be adjacent to the second last turn of the winding.

[0034] Thus, a cooling circuit for the cooling fluid flow can be formed, that is, the cooled cooling fluid can flow from the heat exchanger to the supply main pipe and the cooling pipe (which extends (at least partially) along the coil winding) and finally to the return main pipe, which guides the fluid back to the heat exchanger.

[0035] The cooling pipe 220 may be made of an insulating material (such as plastic), and in order to adapt to the limitations of each case (such as necessary connections, specific distances or lengths, etc.), that is, in order to increase the adaptability of the cooling system, the cooling pipe 220 may include different parts or pipes joined together (such as threaded connection, bonding, or by any other suitable method) to form the entire cooling pipe 220.

[0036] The cooling system 200 may further include a pump 270 to force the cooling fluid through the entire cooling circuit, that is, from the output of the heat exchanger through the entire cooling circuit and back to the input of the heat exchanger. In an example, the flow of the cooling fluid may be clockwise (see the arrow in Figure 1 ) or counterclockwise, that is, the first portion 250 may be downstream relative to the second portion 260, and vice versa.

[0037] Figure 2 shows the Figure 1 amplified portion (see the dashed area) of the transformer 1 of the example. This figure shows a first coil winding turn 301, a portion of the cooling tube 220 arranged alternately between subsequent turns of the coil winding, and a conductive connector 400 arranged at the first location 250. The conductive connector 400 may include a metal piece 401 (such as a plate, a ring, or any other suitable shaped element) to be arranged on or coupled to the cooling tube, and a conductive element 402 (such as a metal wire) that electrically connects at least the side (such as the inner side) of the metal piece 401 to be in contact with the cooling fluid and the turns of the coil winding. In Figure 2 the example, the conductive element connects the metal piece and the first turn of the coil winding. In the example, the metal piece 401 may be made of stainless steel.

[0038] The metal piece 401 may be any metal tube. In the example, the metal piece 401 may be a bushing coupled between two different sections of the cooling tube. In other examples, the metal piece 401 may be a ring inserted inside the cooling tube. In the example, the metal piece 401 may be a plate arranged on the inner side (such as adhered or coupled to the inner wall) of the cooling tube. Thus, the side of the cooling tube 220 to be in contact with the cooling fluid, i.e., the inner side, can be considered to be electrically connected to the turns of the coil winding.

[0039] In an example (not shown), the transformer 1 may include a second conductive connector arranged at the second location 260 according to any one of the disclosed examples. For example, the use of the second conductive connector may be particularly suitable according to the electrical connection of the transformer windings in a three-phase transformer. That is, for example, when the ends of the windings are not grounded, i.e., in the case of a delta, zigzag, or star connection where the neutral point is not grounded.

[0040] In the example, the cooling fluid to be introduced into the cooling tube 220 may be water. In the example, the cooling fluid may be distilled and / or deionized water that may additionally include, for example, a coagulant and / or an additive to prevent corrosion of the cooling tube and increase the operating temperature range. In the example, the cooling fluid may be any fluid (such as water) having a conductivity lower than 5·10 -4 S / m, which substantially reduces the generation of current flow in the cooling fluid, thus avoiding several problems such as heating of the cooling fluid, electrolysis, generation of ions and / or gases.

[0041] In an example, the cooling tube 220 may further include a plurality of windings (not shown) to extend the path of the cooling fluid between one end of the winding and one of the supply main pipe and the return main pipe. By extending the path (i.e., the length traveled by the cooling fluid before reaching the start of the winding and / or after leaving the end of the winding), the resistivity of the cooling fluid is increased, thereby preventing the generation of large currents in the cooling fluid and related problems.

[0042] In an example, the windings may extend the path of the cooling fluid between each end of the winding and the supply main pipe and the return main pipe, respectively. In an example where the coil winding is housed within a cover, the windings may be disposed inside or outside the cover.

[0043] In an example, the windings may include at least one of a helical member or a serpentine member.

[0044] The combination of the "serpentine member" and at least one first conductive connector may improve the function of the transformer, such as in addition to preventing dielectric problems related to high voltage differences at the closure points or related to the flow of current within the cooling fluid.

[0045] Although only a plurality of specific embodiments and examples are disclosed herein, those skilled in the art will understand that other alternative embodiments and / or uses of the disclosed innovations, as well as their obvious modifications and equivalents, are possible. Additionally, the present disclosure covers all possible combinations of the specific embodiments described. The scope of the present disclosure should not be limited by the specific embodiments, but should be determined only by a fair reading of the appended claims.

Claims

1. A non-immersed transformer, comprising: a magnetic core and a coil winding, the coil winding forming a plurality of winding turns around the magnetic core; a cooling system, the cooling system including a cooling pipe for cooling a fluid flow, the cooling pipe extending along the coil winding, and wherein the cooling pipe includes a first portion adjacent to a turn of the coil winding and a second portion adjacent to another turn of the coil winding; and a first conductive connector, the first conductive connector being arranged at one of the first portion and the second portion to electrically connect the inner side of the cooling pipe to the turn of the coil winding.

2. The transformer according to claim 1, wherein the first portion of the cooling pipe is adjacent to one end of the coil winding, and the second portion is adjacent to the other end of the coil winding.

3. The transformer according to claim 1 or 2, further comprising a second conductive connector, such that the first conductive connector is arranged at the first portion and the second conductive connector is arranged at the second portion.

4. The transformer according to claim 1 or 2, wherein the conductive connector includes a metal wire and a metal piece in electrical contact with the inner side of the cooling pipe.

5. The transformer according to claim 1 or 2, wherein the cooling pipe is made of an insulating material.

6. The transformer according to claim 1 or 2, wherein the cooling fluid is water.

7. The transformer according to claim 1 or 2, wherein the cooling system further includes: a heat exchanger; and a feed main pipe and a return main pipe, the feed main pipe and the return main pipe being coupled to the heat exchanger, and wherein the feed main pipe is connected to an input portion of the cooling pipe, and the return main pipe is connected to an output portion of the cooling pipe.

8. The transformer according to claim 7, wherein the feed main pipe and the return main pipe are grounded.

9. The transformer according to claim 7, wherein the cooling pipe further includes a plurality of winding members to extend the path of the cooling fluid between one end of the winding and one of the feed main pipe and the return main pipe.

10. The transformer according to claim 9, wherein the plurality of winding members are arranged inside a coil cover, and the winding turns are accommodated in the coil cover.

11. The transformer according to claim 9, wherein the plurality of winding members are arranged outside a coil cover, and the winding turns are accommodated in the coil cover.

12. The transformer according to claim 1 or 2, wherein the transformer is a high-voltage transformer.

Images