High-capacity on‑load tap‑changing transformer

Abstract

Disclosed in the present invention is a high-capacity on-load tap‑changing transformer, comprising a main tank, wherein a capsule-type conservator is mounted on the upper part of one end of the main tank, an on-load tap changer is mounted at the other end of the main tank, and radiators are mounted externally on two opposite sides of the main tank. An active part inside the main tank consists of windings and a core; the windings include a low-voltage winding, a high-voltage winding, a coarse regulating winding, and a fine regulating winding that are sequentially arranged from inside to outside; the high-voltage winding, the coarse regulating winding, and the fine regulating winding are connected to the on-load tap changer by means of leads. By using coarse and fine regulating structures, the coarse regulating winding and the fine regulating winding can be fully bypassed when the transformer operates at the most negative tap position, thereby effectively reducing stray losses caused by leakage flux, and also lowering resistive losses arising from the resistance of the regulating windings, and thus significantly improving the operational economy and reliability of the transformer.

Description

A large-capacity on-load tap-changing transformer Technical Field

[0001] This invention relates to the field of power transformer technology, and in particular to a large-capacity on-load tap-changing transformer. Background Technology

[0002] On-load tap-changing transformers play a vital role in power systems. They not only stabilize the load center voltage but are also indispensable equipment for connecting the power grid, regulating load current, and improving reactive power distribution.

[0003] The basic methods of on-load tap changer regulation are mainly linear voltage regulation, coarse and fine voltage regulation, and positive-negative voltage regulation. Linear voltage regulation is currently mostly used in off-load tap-changing transformers, and is less commonly used on-load tap changer regulation. Considering the current operation of my country's power system, due to the high stability and low voltage fluctuation of the power grid, and taking into account the economic performance of the products, most on-load tap-changing transformers used in the market adopt positive-negative voltage regulation. Positive-negative voltage regulation has a relatively simple structure and is currently the most widely used on-load tap changer regulation method. Coarse and fine voltage regulation, compared to positive-negative voltage regulation, results in higher transformer costs and is rarely used.

[0004] Transformers are large pieces of equipment in power systems, and like tailor-made clothing, they are customized products. Their design calculations must be based on an analysis of the transformer's operating status and the power grid's operating conditions to select the most suitable design calculation scheme. For some countries with relatively underdeveloped economies or those that are vigorously developing their power industries, and for forward-looking considerations, most power grids are currently operating with a bias towards negative connections, requiring different targeted designs for these situations.

[0005] For transformers that operate in negative tap mode for extended periods, although the forward and reverse voltage regulation structure is relatively simple and the cost is relatively low, the constant reverse connection of the voltage regulation coils during long-term negative tap operation results in high voltage regulation resistance losses and stray losses caused by leakage flux, which is detrimental to the economic operation of the transformer system. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a structurally sound, large-capacity on-load tap-changing transformer, which effectively reduces stray losses caused by leakage flux and lowers resistive losses caused by the resistance of the tap-changing winding itself, thereby significantly improving the economic efficiency and reliability of transformer operation.

[0007] The technical solution adopted in this invention is as follows:

[0008] A large-capacity on-load tap-changing transformer includes a main tank. A capsule-type oil conservator is installed on the upper part of one end of the main tank, and an on-load tap changer is installed at the other end of the main tank. Radiators are installed on the opposite sides of the main tank. The transformer body inside the main tank is composed of windings and an iron core. The windings include a low-voltage winding, a high-voltage winding, a coarse tap-changing winding, and a fine tap-changing winding arranged sequentially from the inside to the outside. The high-voltage winding, the coarse tap-changing winding, and the fine tap-changing winding are connected to the on-load tap changer by leads.

[0009] As a further improvement to the above technical solution:

[0010] The coarse voltage adjusting winding is connected to the high voltage winding at its beginning end, and the coarse voltage adjusting winding is connected to the K terminal and positive terminal of the on-load tap changer at its end, respectively. The coarse voltage adjusting winding is connected to the negative terminal of the on-load tap changer at its beginning end. The switch terminal of the on-load tap changer is connected to the terminal at the end of the fine voltage adjusting winding. By connecting the switch terminal to the positive terminal or the negative terminal, the connection or disconnection of the high voltage winding and the coarse voltage adjusting winding can be switched.

[0011] The fine voltage adjusting winding adopts a linear structure. The leads of the fine voltage adjusting winding are tapped according to the voltage ratio and connected one by one to multiple terminals of the on-load tap changer. The connection or disconnection of the fine voltage adjusting winding is adjusted by sliding the sliding contact on the on-load tap changer.

[0012] The fine voltage adjusting winding adopts radial exit, while the high voltage winding, low voltage winding, and coarse voltage adjusting winding adopt axial exit.

[0013] An electrostatic plate is placed in the 220kV high-voltage area at the upper end of the high-voltage winding. The electrostatic plate has rounded corners, and the size of the rounded corners is consistent with the divergence angle of the end electromagnetic lines. Two shaped corner rings are placed on the inner and outer diameter sides above the electrostatic plate, and the rounded corners of the shaped corner rings are consistent with the divergence angle of the end electromagnetic lines. Oil gap spacers are used to separate adjacent shaped corner rings and between shaped corner rings and the electrostatic plate. A second shaped corner ring is placed on the inner diameter of the lower end of the high-voltage winding.

[0014] The upper end of the high-voltage winding is covered with two layers of insulating molded parts on one side, and then three layers of cardboard are covered on the outside of the insulating molded parts.

[0015] The core adopts a three-phase five-column structure, including three main columns in the middle and two side columns on both sides. The two side columns are arranged in a D-shape with opposite sides. Oil channels are opened in the core. The upper and lower yokes at both ends of the core adopt a T-shaped structure with opposite sides. Lung-shaped magnetic shields are installed in both the upper and lower yokes.

[0016] The current of the on-load tap changer is selected to be 1.2 times the rated current of the high-voltage winding, and three on-load tap changers are selected to form a three-phase circuit.

[0017] The radiators are arranged in an orderly manner and divided into groups, and each group of radiators is equipped with a butterfly valve at the oil inlet and outlet; an upward-blowing fan is installed below each radiator.

[0018] Ladders are provided on the side of the main body oil tank and the side of the oil storage tank.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By employing a coarse and fine voltage regulating structure, this invention can completely detach the coarse and fine voltage regulating windings when the transformer is operating at its most negative tap. This effectively reduces stray losses caused by leakage flux and also reduces resistance losses caused by the resistance of the voltage regulating winding itself, greatly improving the economy and reliability of transformer operation.

[0021] The present invention also includes the following advantages:

[0022] The large-capacity on-load tap-changing transformer has a capacity of 525,000 kVA, a voltage ratio of 232 ± 10 × 1.25% / 21 kV, and a short-circuit impedance of 28%. At the same time, corresponding settings have been made to address the high leakage flux characteristics brought about by the large capacity, so as to reduce the diffusion of leakage flux, reduce stray losses, and avoid local overheating. Attached Figure Description

[0023] Figure 1 is a front view of the present invention.

[0024] Figure 2 is a left view of Figure 1.

[0025] Figure 3 is a top view of Figure 1.

[0026] Figure 4 is a schematic diagram of the wiring of the low-voltage winding of the present invention.

[0027] Figure 5 is a schematic diagram of the wiring of the high-voltage winding and the voltage regulating winding of the present invention.

[0028] Figure 6 is a schematic diagram of the winding arrangement of the present invention.

[0029] Figure 7 is a side view of the upper and lower yokes of the present invention.

[0030] Figure 8 is a schematic diagram of the structure of the iron core of the present invention.

[0031] The components include: 1. Main oil tank; 2. High-voltage neutral point bushing; 3. High-voltage bushing; 4. Low-voltage bushing; 5. Oil conservator; 6. Radiator; 7. On-load tap changer; 8. Coarse voltage adjusting winding; 9. Fine voltage adjusting winding; 10. Ladder; 11. Upper section oil tank; 12. Lower section oil tank; 13. Upper yoke; 14. Lung-shaped magnetic shield; 15. Upper clamp; 16. Lower yoke; 17. Lower clamp; 18. Side column; 30. High-voltage riser seat; 31. High-voltage winding; 32. Static plate; 33. Molded corner ring one; 34. Insulating molded part; 35. Cardboard; 36. Molded corner ring two; 40. Low-voltage riser seat; 41. Low-voltage winding; 60. Fan. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0033] As shown in Figures 1, 2, and 3, a large-capacity on-load tap-changing transformer of this embodiment includes a main tank 1. A capsule-type oil conservator 5 is installed on the upper part of one end of the main tank 1, and an on-load tap changer 7 is installed at the other end of the main tank 1. Radiators 6 are installed on the opposite sides of the main tank 1. The transformer body inside the main tank 1 is composed of windings and an iron core. The windings include a low-voltage winding 41, a high-voltage winding 31, a coarse tap-changing winding 8, and a fine tap-changing winding 9 arranged sequentially from the inside to the outside. The high-voltage winding 31, the coarse tap-changing winding 8, and the fine tap-changing winding 9 are connected to the on-load tap changer 7 by leads.

[0034] In this embodiment, by adopting a coarse and fine voltage adjustment structure, the coarse voltage adjustment winding 8 and the fine voltage adjustment winding 9 can be completely discarded when the transformer is operating at the most negative tap, thereby effectively reducing stray losses caused by leakage flux and reducing resistance losses caused by the resistance of the voltage adjustment winding itself.

[0035] As shown in Figure 5, the first end of the coarse voltage adjusting winding 8 is connected to the high voltage winding 31, and the last end of the coarse voltage adjusting winding 8 is connected to the K terminal and the positive terminal (+) of the on-load tap changer 7, respectively. The first end of the coarse voltage adjusting winding 8 is connected to the negative terminal (-) of the on-load tap changer 7. The switch terminal (O) of the on-load tap changer 7 is connected to the terminal at the end of the fine voltage adjusting winding 9. By connecting the switch terminal (O) to the positive terminal (+) or the negative terminal (-), the connection or disconnection of the high voltage winding 31 and the coarse voltage adjusting winding 8 can be switched.

[0036] In this embodiment, the number of turns of the high voltage winding 31 is the same as the total number of turns of the highest negative tap of the high voltage winding, the number of turns of the coarse voltage adjusting winding 8 is the same as the total number of turns of the fine voltage adjusting winding 9, and the three windings are interconnected by leads through the on-load tap changer 7.

[0037] The fine voltage adjusting winding 9 adopts a linear structure. The leads of the fine voltage adjusting winding 9 are tapped according to the voltage ratio and connected one by one to the multiple terminals of the on-load tap changer 7. The connection or disconnection of the fine voltage adjusting winding 9 is adjusted by sliding the sliding contact on the on-load tap changer 7.

[0038] In one embodiment, the fine voltage adjusting winding 9 is set with ten taps according to the voltage ratio, and eleven leads are brought out. The eleven leads are respectively connected to the (1)-(11) terminals of the on-load tap changer 7. The switch terminal is always connected to the terminal (11). When the sliding contact slides to the terminal (11), the fine voltage adjusting winding 9 is completely disconnected. When the sliding contact slides to the terminal (1), the fine voltage adjusting winding 9 is completely connected.

[0039] In this embodiment, the low-voltage winding 41 is connected using YNd1, as shown in Figure 4.

[0040] In this embodiment, the high-voltage winding 31 adopts an inner-screen continuous winding structure, while the low-voltage winding 41, the coarse voltage adjustment winding 8, and the fine voltage adjustment winding 9 all adopt a spiral winding structure.

[0041] The fine voltage adjusting winding 9 adopts radial extension, while the high voltage winding 31, low voltage winding 41 and coarse voltage adjusting winding 8 adopt axial extension.

[0042] As shown in Figure 6, an electrostatic plate 32 is placed in the 220kV high-voltage area at the upper end of the high-voltage winding 31. The electrostatic plate 32 has rounded corners, and the size of the rounded corners is basically consistent with the angle of divergence of the end electromagnetic wires, so as to avoid electric field concentration, improve the end electric field, and enhance insulation performance.

[0043] Two shaped corner rings 33 are placed on the inner and outer diameter sides above the electrostatic plate 32. The rounded corners of the shaped corner rings 33 are basically consistent with the divergence angle of the electromagnetic wires at the end, so as to improve the high voltage field strength at the end and isolate the discharge channel between high and low voltage, thus playing a good insulating role.

[0044] In this embodiment, the molded corner ring 33 is formed by extruding pulp with excellent insulating properties in a specially designed mold.

[0045] Oil gap spacers are used to separate adjacent forming corner rings 33 and between forming corner rings 33 and static plate 32. While ensuring insulation, the heat generated during winding operation is carried out by the thermal convection properties of oil, thus playing a heat dissipation role.

[0046] In this embodiment, the oil gap spacer between the electrostatic plate 32 and the molded corner ring 33 is made by stacking paper tape and pasting it onto the electrostatic plate 32. The oil gap spacer is also made with rounded corners on both the inner and outer diameter sides to improve the end electric field strength and enhance the insulation performance.

[0047] A shaped corner ring 36 is placed on the lower inner diameter of the high voltage winding 31 to improve the lower electric field between the high and low voltage and enhance the insulation performance.

[0048] The lower end of the high voltage winding 31 has the same potential as the coarse voltage adjusting winding 8, so there is no need to add protective measures such as a protective corner ring between the lower end of the high voltage winding 31 and the coarse voltage adjusting winding 8.

[0049] The upper end of the high voltage winding 31 is covered with two layers of insulating molded parts 34 on one side, and three layers of cardboard 35 are then covered on the outside of the insulating molded parts 34.

[0050] In actual operation, considering the high voltage (i.e. 220kV) at the upper end of the high voltage winding 31, first wrap 10mm insulation on one side, and then wrap the insulation molding 34 and cardboard 35.

[0051] In this embodiment, the insulating molded component 34 and the cardboard 35 are separated by support strips or corrugated cardboard to leave gaps and improve insulation performance. The lead-out molded component starts from the coil lead-out, providing comprehensive protection.

[0052] As shown in Figure 7, the upper yoke 13 and lower yoke 16 located at both ends of the iron core adopt a T-shaped structure arranged in opposite directions, and lung-shaped magnetic shields 14 are installed in both the upper yoke 13 and lower yoke 16.

[0053] In this embodiment, the low-voltage current reaches 14434A. In order to reduce the loss caused by the high current of the product, lung-shaped magnetic shields 14 are placed above and below the coil to effectively introduce the leakage magnetic flux of the coil into the iron core and reduce the leakage magnetic flux entering the steel parts and causing local overheating.

[0054] In this embodiment, by setting up the upper yoke 13 and lower yoke 16 of the T-shaped structure arranged in opposite directions, the leakage magnetic field attracted by the lung-shaped magnetic shield 14 of the upper and lower body can be easily introduced into the yoke at the T-shaped gap; in addition, by appropriately increasing the cross-sectional area of ​​the upper and lower yokes, the magnetic density of the yokes is reduced, ensuring that no local overheating occurs at the magnetic path of the magnetic shield of the body.

[0055] Meanwhile, a magnetic shield is welded to the inner wall of the main body oil tank 1 to prevent the oil tank from overheating.

[0056] As shown in Figure 8, the core adopts a three-phase five-column structure, including three main columns in the middle and two side columns 18 on both sides. The two side columns 18 are D-shaped structures arranged facing each other; oil channels are opened in the core.

[0057] By adopting a D-shaped structure for the side columns 18, compared to the conventional elliptical structure, the center distance from the main column is reduced, thus decreasing the weight of the silicon steel sheets and lowering costs. Calculations show that the weight of the silicon steel sheets is reduced by approximately 500 kg.

[0058] In this embodiment, the internal temperature rise of the iron core is reduced by appropriately adding oil channels to the iron core.

[0059] In this embodiment, the iron limb plates extending from the upper clamp 15 and lower clamp 17 are made of non-magnetic steel plates to avoid local overheating. Because the core pull plate is close to the low-voltage coil, it is also made of non-magnetic steel plate, and the magnetic shielding gap is increased to reduce eddy current losses on the pull plate surface.

[0060] High-voltage neutral point bushing 2, high-voltage bushing 3, and low-voltage bushing 4 are sequentially installed on the top surface of the main body oil tank 1. The bushing current is selected according to the rated current of the winding being greater than or equal to 1.2 times. All bushings are installed on the corresponding riser base.

[0061] The current of the on-load tap changer 7 is selected to be 1.2 times the rated current of the high-voltage winding 31. Due to the large current, three on-load tap changers 7 are selected to form a three-phase circuit.

[0062] The current of the low-voltage bushing 4 reaches 20000A. Due to the large current, the leakage magnetic field is also large. The low-voltage riser seat 40 located below the low-voltage bushing 4 is made of non-magnetic steel plate. The upper surface of the cover plate of the low-voltage riser seat 40 is also welded with a copper plate to block the leakage magnetic field formed by the low-voltage current and prevent the low-voltage riser seat 40 from overheating.

[0063] In this embodiment, the connection between the low-pressure riser 40 and the flange is made of non-magnetic stainless steel bolts to avoid overheating of the bolts.

[0064] The high-voltage bushing 3 is an oil-SF6 bushing. The high-voltage bushing 3 is installed on the high-voltage riser 30. The lower part of the high-voltage bushing 3 is immersed in transformer oil, and the upper part of the high-voltage bushing 3 is in the SF6 gas of GIS.

[0065] The radiators 6 are arranged in an orderly manner and divided into groups. Each group of radiators 6 is equipped with a butterfly valve at the oil inlet and outlet so that the radiator 6 can be disassembled and installed individually when oil leakage or other faults occur during years of operation. An upward-blowing fan 60 is installed below the radiator 6.

[0066] In one embodiment, the radiator 6 is installed in four groups, arranged in an orderly manner on opposite sides of the main body oil tank 1.

[0067] In this embodiment, the fan 60 blows air upwards, causing hot air to flow upwards, resulting in higher heat dissipation efficiency.

[0068] In this embodiment, the fan power cable is connected to the air-cooled control cabinet. Simultaneously, the transformer temperature signal is also connected to the air-cooled control cabinet. The air-cooled control cabinet controls the opening and closing of the fans 60 in groups based on the designed temperature information, minimizing fan energy consumption. In practice, the air-cooled control cabinet is installed separately on the floor.

[0069] Ladders 10 are installed on the side of the main oil tank 1 and the side of the oil storage tank 5 respectively. The ladders 10 are installed at an angle to facilitate the corresponding operations by personnel during installation and maintenance.

[0070] In this embodiment, the main body oil tank 1 is composed of an upper oil tank 11 and a lower oil tank 12 connected by bolts; an oil injection valve and an oil drain valve are installed at the end of the lower oil tank 12.

[0071] In this embodiment, the large-capacity on-load tap-changing transformer has a capacity of 525,000 kVA, a voltage ratio of 232 ± 10 × 1.25% / 21 kV, and a short-circuit impedance of 28%. At the same time, corresponding settings have been made to address the high leakage flux characteristics brought about by the large capacity, so as to reduce the diffusion of leakage flux, reduce stray losses, and avoid local overheating.

[0072] The working principle of this invention is as follows:

[0073] When the most negative tap is engaged, only the low-voltage winding 41 and the high-voltage winding 31 are engaged in operation. That is, the switch terminal (O) of the on-load tap changer 7 is connected to the negative terminal (-), and the sliding contact is connected to the terminal (11). This allows the coarse voltage adjustment winding 8 and the fine voltage adjustment winding 9 to be disconnected. At this time, the product has low leakage flux, low loss, and high operating economy.

[0074] Since this 220kV product has a capacity of 525,000kVA, it is a typical large-capacity product. The result of large capacity is large leakage flux. Therefore, appropriately reducing leakage flux has a great effect on the economic efficiency of operation.

[0075] When the voltage can be stabilized at the rated tap, simply connect the switch terminal (O) of the on-load tap changer 7 to the positive terminal (+), and the sliding contact will be switched to terminal (11).

[0076] If the voltage needs to be adjusted to the positive tap, connect the switch terminal (O) of the on-load tap changer 7 to the positive terminal (+), and the sliding contact can be switched to the corresponding terminal (one of 1-11). At this time, if the sliding contact is connected to the terminal (1), it will be in the most positive tap, i.e., the +10 tap.

[0077] This invention employs a coarse and fine voltage regulating structure, which effectively reduces stray losses caused by leakage flux and reduces resistance losses caused by the resistance of the regulating winding itself, thus greatly improving the economy and reliability of transformer operation.

[0078] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0079] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A large-capacity on-load tap-changing transformer, comprising a main body tank (1), characterized in that: The main body oil tank (1) is equipped with a capsule-type oil storage tank (5) at one end of the upper part, and an on-load tap changer (7) is installed at the other end of the main body oil tank (1). Radiators (6) are installed on the opposite sides of the main body oil tank (1). The internal body of the main body oil tank (1) is composed of windings and an iron core. The windings include a low-voltage winding (41), a high-voltage winding (31), a coarse voltage adjustment winding (8), and a fine voltage adjustment winding (9) arranged from the inside to the outside. The high-voltage winding (31), the coarse voltage adjustment winding (8), and the fine voltage adjustment winding (9) are connected to the on-load tap changer (7) by lead wires.

2. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The coarse voltage adjusting winding (8) is connected to the high voltage winding (31) at its first end, and the ends of the coarse voltage adjusting winding (8) are connected to the K terminal and the positive terminal of the on-load tap changer (7) respectively. The first end of the coarse voltage adjusting winding (8) is connected to the negative terminal of the on-load tap changer (7). The switch terminal of the on-load tap changer (7) is connected to the terminal at the end of the fine voltage adjusting winding (9). By connecting the switch terminal to the positive terminal or the negative terminal, the connection or disconnection of the high voltage winding (31) and the coarse voltage adjusting winding (8) can be switched.

3. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The fine voltage adjusting winding (9) adopts a linear structure. The leads of the fine voltage adjusting winding (9) are tapped according to the voltage ratio and connected one by one to multiple terminals of the on-load tap changer (7). The connection or disconnection of the fine voltage adjusting winding (9) is adjusted by sliding the sliding contact on the on-load tap changer (7).

4. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The fine voltage adjusting winding (9) has radial leads, while the high voltage winding (31), low voltage winding (41) and coarse voltage adjusting winding (8) have axial leads.

5. A large-capacity on-load tap-changing transformer as described in claim 4, characterized in that: An electrostatic plate (32) is placed in the 220kV high-voltage area at the upper end of the high-voltage winding (31). The electrostatic plate (32) has rounded corners, and the size of the rounded corners is consistent with the divergence angle of the end electromagnetic lines. Two shaped corner rings (33) are placed on the inner and outer diameter sides above the electrostatic plate (32). The rounded corners of the shaped corner rings (33) are consistent with the divergence angle of the end electromagnetic lines. Oil gap pads are used to separate adjacent shaped corner rings (33) and between shaped corner rings (33) and the electrostatic plate (32). A shaped corner ring (36) is placed on the inner diameter of the lower end of the high-voltage winding (31).

6. A large-capacity on-load tap-changing transformer as described in claim 4, characterized in that: The upper end of the high voltage winding (31) is covered with two layers of insulating molded parts (34) on one side, and three layers of cardboard (35) are then covered on the outside of the insulating molded parts (34).

7. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The core adopts a three-phase five-column structure, including three main columns in the middle and two side columns (18) on both sides. The two side columns (18) are arranged in a D-shape with opposite sides. Oil channels are opened in the core. The upper yoke (13) and lower yoke (16) located at both ends of the core adopt a T-shaped structure with opposite sides. Lung-shaped magnetic shields (14) are installed in both the upper yoke (13) and lower yoke (16).

8. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The current of the on-load tap changer (7) is selected to be 1.2 times the rated current of the high-voltage winding (31), and three on-load tap changers (7) are selected to form a three-phase circuit.

9. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: The radiators (6) are arranged in an orderly manner and divided into groups. Each group of radiators (6) has a butterfly valve installed at the oil inlet and outlet. A fan (60) that blows air upwards is installed below the radiator (6).

10. A large-capacity on-load tap-changing transformer as described in claim 1, characterized in that: Ladders (10) are provided on the side of the main body oil tank (1) and the side of the oil storage tank (5).

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