CN114566367A - On-load tap changer and offshore booster station with same - Google Patents

Abstract

The invention relates to an on-load tap changer and an offshore booster station provided with the same, wherein the on-load tap changer comprises an iron core column, a low-voltage winding, a high-voltage winding and a tap winding, wherein the iron core column, the low-voltage winding, the high-voltage winding and the tap winding are sequentially and concentrically sleeved from inside to outside; the voltage regulating winding comprises a coarse regulating winding and a fine regulating winding, the coarse regulating winding comprises an upper coarse regulating unit and a lower coarse regulating unit which are connected in parallel, the fine regulating winding comprises an upper fine regulating unit and a lower fine regulating unit which are connected in parallel, and the upper coarse regulating unit, the upper fine regulating unit, the lower fine regulating unit and the lower coarse regulating unit are sequentially arranged at intervals from top to bottom along the axial direction of the iron core column. According to the on-load tap changing transformer, the upper coarse adjusting unit, the upper fine adjusting unit, the lower fine adjusting unit and the lower coarse adjusting unit are sequentially arranged along the axial direction instead of the radial direction, so that the occupied area of the on-load tap changing transformer is effectively reduced, and the active effect of reducing the size of an offshore booster station is achieved.

Description

On-load tap changer and offshore booster station with same

Technical Field

The invention relates to the technical field of on-load tap changing transformer manufacturing, in particular to an on-load tap changing transformer and an offshore booster station with the same.

Background

At present, the environmental pollution and the greenhouse gas emission are increasingly serious, wind power generation is regarded as a scheme which can effectively slow down the climate change, improve the energy safety and promote the low-carbon economic growth globally, and is highly concerned by governments, organizations, enterprises and the like of various countries. In addition, wind power has become one of the fastest growing energy sources in the world in recent years due to the fact that wind power technology is relatively mature and has higher cost effectiveness and resource effectiveness.

The country has vast breadth, long coastlines, excellent congenital conditions in the east coastal region of China, developed economy, lack of conventional energy, high environmental protection requirements, rich wind energy resources and strong industrial foundation. Therefore, compared with onshore wind power, the method has good conditions for developing and constructing offshore wind power.

With the development of offshore wind power generation technology, offshore wind power plants are further and further distant from each other, and the scale of the wind power plants is larger and further, the traditional method for arranging the onshore booster station on land is no longer suitable due to large loss of low-voltage transmission lines, large copper material consumption of cables and high cost, and in order to safely, reliably and economically send electric energy generated by the offshore wind power plants to the inland, the offshore booster station is required to be arranged on the sea. Therefore, the electric energy generated by the fan group of the offshore wind farm is centrally transmitted to the offshore booster station through the submarine cable current collection link, and then is boosted and transmitted to the onshore transformer substation through the transformer of the offshore booster station to complete electric power transmission.

The offshore booster station is generally divided into an upper block and an offshore platform steel structure and is a boosting, power distribution and control center of an offshore wind farm. The transformer is composed of two or more coil windings wound on the same iron core, and the windings are connected through an alternating magnetic field and work according to the electromagnetic induction principle so as to transmit electric energy, convert voltage and current in a power system and meet the requirements of power transmission and utilization.

The transformer is used as an important component of the offshore wind farm, is a hub of the power transmission of the whole offshore wind farm, and the weight, the volume and the loss performance of the transformer are decisive factors for restricting the weight, the size and the energy consumption of the whole offshore booster station. Therefore, how to reduce the total weight of the transformer and the occupied area of the transformer on the premise of ensuring reliability, so as to reduce the investment cost of the whole offshore booster station platform, is a problem to be solved urgently by the technical personnel in the field.

Disclosure of Invention

Therefore, in order to solve the problem of large occupied area of the transformer, the on-load tap changing transformer and the offshore booster station with the on-load tap changing transformer need to be provided, and the on-load tap changing transformer and the offshore booster station with the on-load tap changing transformer can achieve the technical effect of reducing the occupied area.

According to one aspect of the application, an on-load tap changing transformer is provided, and comprises a core limb, a low-voltage winding, a high-voltage winding and a tap changing winding, wherein the core limb, the low-voltage winding, the high-voltage winding and the tap changing winding are sequentially and concentrically sleeved from inside to outside;

the voltage regulating winding comprises a coarse regulating winding and a fine regulating winding, the coarse regulating winding comprises an upper coarse regulating unit and a lower coarse regulating unit which are connected in parallel, the fine regulating winding comprises an upper fine regulating unit and a lower fine regulating unit which are connected in parallel, and the upper coarse regulating unit, the upper fine regulating unit, the lower fine regulating unit and the lower coarse regulating unit are sequentially arranged at intervals from top to bottom along the axial direction of the iron core column.

The upper coarse adjustment unit, the upper fine adjustment unit, the lower fine adjustment unit and the lower coarse adjustment unit which form the voltage regulation winding are sequentially arranged along the axial direction of the iron core column instead of being arranged along the radial direction, so that the size of the on-load voltage regulation transformer in the radial direction of the iron core column is effectively reduced, the floor area of the on-load voltage regulation transformer is further reduced, and the active effect on reducing the volume of the offshore booster station provided with the on-load voltage regulation transformer is achieved.

In one embodiment, the upper coarse tuning unit, the lower coarse tuning unit, the upper fine tuning unit, and the lower fine tuning unit have the same size in the radial direction of the core limb.

In one embodiment, the upper coarse tuning unit and the lower coarse tuning unit are symmetrically arranged by taking a virtual plane as a symmetry plane, and the virtual plane is perpendicular to the axial direction of the iron core column; and/or

The upper fine adjustment unit and the lower fine adjustment unit are symmetrically arranged by taking a virtual plane as a symmetry plane, and the virtual plane is perpendicular to the axial direction of the iron core column.

In one embodiment, the low voltage winding includes a first low voltage winding and a second low voltage winding, and the first low voltage winding and the second low voltage winding are arranged at intervals in an axial direction of the core barrel.

In one embodiment, the upper coarse tuning unit and the upper fine tuning unit are sleeved outside the first low-voltage winding, and the lower coarse tuning unit and the lower fine tuning unit are sleeved outside the second low-voltage winding.

In one embodiment, the outlet end of the first low-voltage winding is positioned at one end of the first low-voltage winding, which is far away from the second low-voltage winding;

And the outlet end of the second low-voltage winding is positioned at one end of the second low-voltage winding, which is far away from the first low-voltage winding.

In one embodiment, the first low voltage winding and the second low voltage winding are the same size in the radial direction of the core limb.

In one embodiment, the first low-voltage winding and the second low-voltage winding are symmetrically arranged with a virtual plane as a symmetry plane, and the virtual plane is perpendicular to the axial direction of the core barrel.

In one embodiment, the high-voltage winding includes a first high-voltage winding and a second high-voltage winding, the first high-voltage winding and the second high-voltage winding are connected in parallel with each other, and the first high-voltage winding and the second high-voltage winding are arranged side by side in an axial direction of the core barrel.

According to another aspect of the application, an offshore booster station is provided, comprising the on-load tap changer.

According to the offshore booster station, the coarse regulating winding and the fine regulating winding are arranged along the axial direction of the iron core column instead of the radial direction, so that the size of the on-load tap changer in the radial direction is reduced. And moreover, a coarse-fine regulation and voltage regulation mode is adopted, a coarse regulation winding is connected in series during rated tapping, and no voltage regulation is carried out during most negative tapping, so that the effect that the load losses of the on-load tap-changing transformer at each tapping position are basically the same is realized, the load loss of the most negative tapping of the on-load tap-changing transformer is reduced, the on-load tap-changing transformer is more environment-friendly, the cooling capacity is reduced, the number of radiators of the on-load tap-changing transformer is reduced, the weight of the radiator for radiating the on-load tap-changing transformer is reduced, the floor area of the radiator is reduced, and finally, the size and the weight of the offshore booster station are reduced.

Drawings

Fig. 1 is a schematic structural diagram of an on-load tap changer according to an embodiment of the present invention;

fig. 2 is a schematic wiring diagram of a high voltage winding of an on-load tap changer according to an embodiment of the present invention;

fig. 3 is a schematic wiring diagram of a low-voltage winding of an on-load tap changer according to an embodiment of the present invention.

The reference numbers indicate:

100. an on-load tap changer; 120. a core limb; 140. a low voltage winding; 141. a first low voltage winding; 143. a second low voltage winding; 160. a high voltage winding; 161. a first high voltage winding; 163. a second high voltage winding; 180. a voltage regulating winding; 181. coarse winding; 1812. an upper coarse adjustment unit; 1814. a lower coarse adjustment unit; 183. fine-tuning the winding; 1832. an upper fine adjustment unit; 1834. and a lower fine adjustment unit.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, but are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise.

In the present invention, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as being permanently connected, detachably connected, or integral; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "above," and "over" a second feature may be directly on or obliquely above the second feature, or simply mean that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1 and fig. 2, fig. 1 shows a structural schematic diagram of an on-load tap changer in an embodiment of the present invention, and fig. 2 shows a wiring schematic diagram of a high-voltage winding of the on-load tap changer in an embodiment of the present invention.

An embodiment of the present invention provides an offshore booster station (not shown), in which electric energy generated by a fan group of an offshore wind farm is centrally transmitted to the offshore booster station via a submarine cable power collection link, and then boosted by a transformer of the offshore booster station to a shore substation to complete power transmission. The offshore booster station comprises an on-load tap changing transformer 100 for adjusting voltage, the on-load tap changing transformer 100 comprises a core limb 120, a low-voltage winding 140, a high-voltage winding 160 and a tap changing winding 180, and the core limb 120, the low-voltage winding 140, the high-voltage winding 160 and the tap changing winding 180 are sequentially and concentrically sleeved from inside to outside to form a whole. It is understood that the materials, the number of turns, and other manufacturing parameters of the low voltage winding 140, the high voltage winding 160, and the voltage regulating winding 180 may be set as desired.

With reference to fig. 1 and 2, the core leg 120 is one of a three-phase three-limb iron core or a three-phase five-limb iron core, and the core leg 120 is formed by stacking high-quality grain-oriented cold-rolled silicon steel sheets. It is to be understood that the specific configuration of the leg core 120 is not limited thereto, and may be set as needed to meet various requirements.

The low-voltage winding 140 is sleeved outside the core limb 120, and the central axis of the low-voltage winding 140 coincides with the central axis of the core limb 120. The low voltage winding 140 is in a split form and includes a first low voltage winding 141 and a second low voltage winding 143. The first and second low voltage windings 141 and 143 are disposed at intervals in the axial direction of the core leg 120.

Further, the rated voltage of the first low-voltage winding 141 and the rated voltage of the second low-voltage winding 143 are the same, and the rated capacity of the first low-voltage winding 141 and the rated capacity of the second low-voltage winding 143 are also completely the same. Further, the first low voltage winding 141 and the second low voltage winding 143 are symmetrically disposed with a virtual plane perpendicular to the axial direction of the core leg 120 as a symmetry plane, the first low voltage winding 141 and the second low voltage winding 143 have the same size in the radial direction of the core leg 120, and the first low voltage winding 141 and the second low voltage winding 143 have the same position in the magnetic field.

In this way, the first low voltage winding 141 and the second low voltage winding 143 can work independently, or can work cooperatively when connected to the circuit. Since the rated voltage and the rated capacity of the first low-voltage winding 141 and the second low-voltage winding 143 are the same, an induced voltage can be prevented from being generated between the first low-voltage winding 141 and the second low-voltage winding 143, and the first low-voltage winding 141 and the second low-voltage winding 143 can be ensured to operate independently without interference.

Furthermore, the first low-voltage winding 141 is of a double-layer spiral structure with an upper outgoing line, the outgoing line end of the first low-voltage winding 141 is located at one end of the first low-voltage winding 141, which is far away from the second low-voltage winding 143, the second low-voltage winding 143 is of a double-layer spiral structure with a lower outgoing line, and the outgoing line end of the second low-voltage winding 143 is located at one end of the second low-voltage winding 143, which is far away from the first low-voltage winding 141.

In this way, the first low-voltage winding 141 and the second low-voltage winding 143 have opposite current directions at the head end and the tail end, so that the end magnetic field can be greatly cancelled, and the problem of local overheating of the metal structural member due to leakage flux generated by a large current can be solved.

Referring to fig. 1 and fig. 2, the high voltage winding 160 is sleeved outside the low voltage winding 140, and a central axis of the high voltage winding 160 coincides with central axes of the core leg 120 and the low voltage winding 140. The high voltage winding 160 includes a first high voltage winding 161 and a second high voltage winding 163, the first high voltage winding 161 and the second high voltage winding 163 are arranged side by side in the axial direction of the core limb 120, and the first high voltage winding 161 and the second high voltage winding 163 are connected in parallel with each other.

Further, since the voltages of the first high-voltage winding 161 and the second high-voltage winding 163 reach a maximum value at the middle positions thereof in the axial direction, high-voltage head ends are drawn from the middle portions of the first high-voltage winding 161 and the second high-voltage winding 163 in the axial direction for end insulation.

With continued reference to fig. 1 and 2, the voltage regulating winding 180 includes a coarse regulating winding 181 and a fine regulating winding 183, and the coarse regulating winding 181 and the fine regulating winding 183 are arranged along the axial direction of the core leg 120. Coarse tuning winding 181 comprises upper coarse tuning unit 1812 and lower coarse tuning unit 1814, upper coarse tuning unit 1812 and lower coarse tuning unit 1814 are connected in parallel with each other, and the central axes of upper coarse tuning unit 1812 and lower coarse tuning unit 1814 are coincident with the central axis of core leg 120. The fine tuning winding 183 includes an upper fine tuning unit 1832 and a lower fine tuning unit 1834, the upper fine tuning unit 1832 and the lower fine tuning unit 1834 are connected in parallel, and the central axes of the upper fine tuning unit 1832 and the lower fine tuning unit 1834 coincide with the central axis of the core limb 120.

The upper coarse adjustment unit 1812, the upper fine adjustment unit 1832, the lower fine adjustment unit 1834, and the lower coarse adjustment unit 1814 are sequentially arranged at intervals from top to bottom along the axial direction of the core rod 120, and the upper fine adjustment unit 1832 and the lower fine adjustment unit 1834 are located between the upper coarse adjustment unit 1812 and the lower coarse adjustment unit 1814. It is to be understood that the upper side in the present application refers to the upper side in fig. 1, and the lower side in the present application refers to the lower side in fig. 1.

In this way, the upper coarse tuning unit 1812, the upper fine tuning unit 1832, the lower fine tuning unit 1834, and the lower coarse tuning unit 1814 that constitute the voltage-regulating winding 180 are sequentially arranged along the axial direction of the core limb 120, rather than being arranged along the radial direction of the core limb 120, thereby effectively reducing the size of the on-load tap-changing transformer 100 in the radial direction, further reducing the floor space of the on-load tap-changing transformer 100, and playing a positive role in reducing the volume of the offshore booster station.

Further, the upper rough adjusting unit 1812 and the lower rough adjusting unit 1814 are spaced in the axial direction of the core limb 120, the upper rough adjusting unit 1812 and the lower rough adjusting unit 1814 have the same size in the radial direction of the core limb 120, and the upper rough adjusting unit 1812 and the lower rough adjusting unit 1814 are symmetrically arranged with a virtual plane perpendicular to the axial direction as a plane of symmetry. The upper fine adjustment unit 1832 and the lower fine adjustment unit 1834 are arranged at intervals in the axial direction of the core limb 120, the upper fine adjustment unit 1832 and the lower fine adjustment unit 1834 have the same size in the radial direction of the core limb 120 and are equal to the size of the upper coarse adjustment unit 1812 and the lower coarse adjustment unit 1814, and the upper fine adjustment unit 1832 and the lower fine adjustment unit 1834 are arranged symmetrically with a plane perpendicular to the axial direction as a plane of symmetry. Wherein the virtual planes are coplanar with the symmetry planes of the first and second low voltage windings 141 and 143.

In this way, the upper coarse tuning unit 1812 and the lower coarse tuning unit 1814 have the same position in the magnetic field, the upper fine tuning unit 1832 and the lower fine tuning unit 1834 have the same position in the magnetic field, the upper coarse tuning unit 1812 and the upper fine tuning unit 1832 correspondingly surround the first low-voltage winding 141, and the lower coarse tuning unit 1814 and the lower fine tuning unit 1834 correspondingly surround the second low-voltage winding 143, so as to ensure that the two ends of the voltage regulating winding 180 in the axial direction have the same working condition.

In some embodiments, the on-load tap changer 100 further comprises a coarse-fine tap changer, and the adjustment of the high-voltage on the high-voltage side can be realized by changing the number of turns of the fine-fine tap changer adjusting the connection of the voltage-regulating winding 180. Specifically, the coarse tuning winding 181 is connected in series when the rated tapping voltage is applied, and no voltage regulation is applied when the most negative tapping voltage is applied, so that the load losses of the on-load tap-changing transformer 100 at each tapping position are basically the same, and the load loss of the most negative tapping of the on-load tap-changing transformer 100 is reduced.

In some embodiments, as shown in fig. 2 and 3, the high voltage winding 160 and the tap winding 180 of the on-load tap changer 100 are connected in a "Y" shape, and the low voltage winding 140 is connected in a delta shape. The working principle of the voltage regulating winding 180 is as follows:

When the tapping position is located at "-" and the contact of the regulating switch K is changed from 9 → 1, eight-gear change of most negative tapping voltage → rated voltage can be realized; an eight-gear shift of rated tap voltage → maximum tap voltage can be achieved when the tap position is at "+" and the contact of the regulating switch K is shifted from 9 → 1.

Specifically, when the switch is switched to the "-" position, the coarse tuning winding 181 is not connected to the circuit, and the number of turns of the fine tuning voltage winding 180 connected to the circuit can be adjusted by the adjusting switch K, so that the high voltage can be adjusted within a certain range. When the contact of the regulating switch K moves to the position of "9", neither the coarse regulating winding 181 nor the fine regulating winding 183 is connected to the circuit, and the high-voltage side of the on-load tap-changing transformer 100 is the most negative tap voltage. When the contact of the regulating switch K moves to "1", the coarse regulating winding 181 is not connected to the circuit and the fine regulating winding 183 is connected to the circuit, and the high-voltage side of the on-load tap-changing transformer 100 is rated tap voltage.

When the switch is switched to a plus gear, the coarse adjusting winding 181 is connected to the circuit, and the number of turns of the fine adjusting winding 183 connected to the circuit can be adjusted through the adjusting switch K, so that the adjustment of the high-voltage within a certain range is realized. When the contact of the regulating switch K moves to "9", the coarse regulating winding 181 is connected to the circuit and the fine regulating winding 183 is not connected to the circuit, so that the high-voltage side of the on-load tap-changing transformer 100 is the rated tap voltage. When the contact of the regulating switch K moves to "1", the coarse regulating winding 181 is connected to the circuit and the fine regulating winding 183 is connected to the circuit, and the high-voltage side of the on-load tap-changing transformer 100 has the maximum tap voltage.

It is understood that the connection mode of the on-load tap changer 100 is not limited thereto, and may be set as required to meet different requirements.

In the on-load tap changer 100 and the offshore booster station provided with the same, the coarse tuning winding 181 and the fine tuning winding 183 are arranged in the axial direction of the core limb 120 instead of in the radial direction, so that the size of the on-load tap changer 100 in the radial direction is reduced. Moreover, a coarse adjustment and fine adjustment mode is adopted, a coarse adjustment winding 181 is connected in series during rated tapping, and no voltage adjustment is carried out during most negative tapping, so that the effect that the load losses of the on-load tap-changing transformer 100 at each tapping position are basically the same is realized, the load loss of the most negative tapping of the on-load tap-changing transformer 100 is reduced, the on-load tap-changing transformer 100 is more environment-friendly, the cooling capacity is reduced, the number of radiators of the on-load tap-changing transformer 100 is reduced, the weight of the radiator for radiating the on-load tap-changing transformer 100 is reduced, the floor area of the radiator is reduced, and finally, the volume and the weight of the offshore booster station are reduced.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims (10)

1. An on-load tap changing transformer is characterized by comprising an iron core column, a low-voltage winding, a high-voltage winding and a tap changing winding, wherein the iron core column, the low-voltage winding, the high-voltage winding and the tap changing winding are sequentially and concentrically sleeved from inside to outside;

the voltage regulating winding comprises a coarse regulating winding and a fine regulating winding, the coarse regulating winding comprises an upper coarse regulating unit and a lower coarse regulating unit which are connected in parallel, the fine regulating winding comprises an upper fine regulating unit and a lower fine regulating unit which are connected in parallel, and the upper coarse regulating unit, the upper fine regulating unit, the lower fine regulating unit and the lower coarse regulating unit are sequentially arranged at intervals from top to bottom along the axial direction of the iron core column.

2. The on-load tap changer of claim 1, wherein the upper coarse tuning unit, the lower coarse tuning unit, the upper fine tuning unit, and the lower fine tuning unit are the same size in a radial direction of the core limb.

3. The on-load tap changer of claim 1, wherein the upper coarse tuning unit and the lower coarse tuning unit are symmetrically arranged with a virtual plane as a symmetry plane, and the virtual plane is perpendicular to an axial direction of the core limb; and/or

The upper fine adjustment unit and the lower fine adjustment unit are symmetrically arranged by taking a virtual plane as a symmetrical plane, and the virtual plane is perpendicular to the axial direction of the iron core column.

4. The on-load tap changer of claim 1, wherein the low voltage winding comprises a first low voltage winding and a second low voltage winding, and the first low voltage winding and the second low voltage winding are arranged at intervals along an axial direction of the core limb.

5. The on-load tap changer of claim 4, wherein the upper coarse tuning unit and the upper fine tuning unit are sleeved outside the first low-voltage winding, and the lower coarse tuning unit and the lower fine tuning unit are sleeved outside the second low-voltage winding.

6. The on-load tap changer of claim 4, wherein the outlet end of the first low-voltage winding is located at one end of the first low-voltage winding, which is far away from the second low-voltage winding;

and the wire outlet end of the second low-voltage winding is positioned at one end of the second low-voltage winding, which is far away from the first low-voltage winding.

7. The on-load tap changer of claim 4, wherein the first low voltage winding and the second low voltage winding are the same size in a radial direction of the core leg.

8. The on-load tap changer of claim 4, wherein the first low voltage winding and the second low voltage winding are symmetrically arranged with a virtual plane as a symmetry plane, and the virtual plane is perpendicular to the axial direction of the core limb.

9. The on-load tap changer of claim 1, wherein the high voltage winding comprises a first high voltage winding and a second high voltage winding, the first high voltage winding and the second high voltage winding are connected in parallel with each other, and the first high voltage winding and the second high voltage winding are arranged side by side in an axial direction of the core limb.

10. An offshore booster station, comprising an on-load tap changer according to any one of claims 1 to 9.

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