Double-body 220kV step-down phase-shifting transformer and method

Abstract

The invention relates to a double-body 220kV step-down phase-shifting transformer and a method, and belongs to the technical field of three-phase self-coupling phase-shifting transformers. According to the technical scheme, 220 kV high voltage of an autotransformer is connected with a power transmission line transmitting 220 kV, 110 kV medium voltage of the autotransformer is divided into two paths, one path is medium voltage L1 which does not have a phase shifting function, only voltage transformation does not shift phase, and the autotransformer is the same as a common autotransformer; and the other path is medium voltage L2, has a phase shifting function, and is closed with 110kV medium voltage of other power grids, the phase is continuously adjustable, and the power flow of a connection line is continuously controllable. According to the 220kV three-phase self-coupling on-load transformer, the phase shifting function is added on a common 220kV three-phase self-coupling on-load transformer, the phase is continuously adjustable, and the requirement for continuous and controllable branch power flow is met; the double-bus parallel connection problem can be solved, the loop closing function is achieved, the requirement for load non-power-cut transfer supply during line maintenance and after-maintenance input is met, the power supply reliability and safety of a power grid are improved, and the development requirement of an intelligent power distribution network is met.

Description

Technical Field

[0001] The invention relates to a double-body 220kV step-down phase-shifting transformer and a method thereof, belonging to the technical field of three-phase auto-coupling phase-shifting transformers. Background Art

[0002] Three-phase three-winding autotransformers are often used as interconnecting transformers in power systems, usually with three windings: high voltage, medium voltage and low voltage. Three-phase three-winding autotransformers are widely used due to their large capacity, low loss and low cost. With the increase in power load density, the grid structure has become more complex, and dual power supply or even multi-power supply has become more and more common. It has become an inevitable trend to realize the parallel connection of dual buses through closed-loop operation. The existing technology 220kV three-phase autotransformer usually has a high-voltage side voltage of 220kV and a medium-voltage side voltage of 110kV. When the autotransformer in the line is used as a step-down transformer to transmit power from the high-voltage side to the medium-voltage side, due to the complex and changeable flow of the line transmission channel of the three-phase three-winding autotransformer, the phase angle difference on both sides of the medium-voltage 110kV step-down line is large. When the line is closed, a large steady-state current and impact current may be generated in the power grid, which may easily cause the protection system of the power grid to malfunction and cause a power outage. How to accurately adjust the voltage phase angle on both sides of the line and solve the phase angle difference on both sides of the step-down line of the three-phase autotransformer is a technical problem that needs to be solved in this field. Summary of the invention

[0003] The purpose of the present invention is to provide a double-body 220kV step-down phase-shifting transformer and method, which adds a phase-shifting function to an ordinary 220kV three-phase auto-coupling on-load transformer, and the phase is continuously adjustable to meet the demand for continuous control of branch currents; it can not only solve the problem of double bus parallel connection, but also has the function of loop closing, meet the demand for load power transfer without interruption during line maintenance and after-maintenance, improve the reliability and safety of power supply of the power grid, meet the development requirements of the intelligent distribution network, and solve the above-mentioned technical problems existing in the existing technology.

[0004] The technical solution of the present invention is: A double-body 220kV step-down phase-shifting transformer comprises an autocoupler unit and a phase-shifting unit, wherein the autocoupler unit is called an autotransformer, and the phase-shifting unit is called a phase-shifting transformer. The autocoupler unit and the phase-shifting unit are two bodies, namely, an autotransformer body and a phase-shifting transformer body, and the two bodies are placed in the same transformer oil tank; the voltage regulating switch of the autotransformer is arranged next to the autotransformer, and the phase-adjusting switch of the phase-shifting transformer is arranged next to the phase-shifting transformer; the 220kV high voltage of the autotransformer is connected to a 220kV transmission line, and the 110kV medium voltage of the autotransformer is divided into two paths, one of which is a medium voltage L1 without a phase-shifting function, and only transforms the voltage without phase-shifting, which is the same as an ordinary autotransformer; the other is a medium voltage L2 with a phase-shifting function, which is looped with the 110kV medium voltage of other power grids, and the phase is continuously adjustable, and the interconnection line flow is continuously controllable.

[0005] The phase-shifting transformer body includes a phase-shifting transformer core, an excitation winding and a phase-adjusting winding. The ends of the three-phase windings of the phase-shifting transformer are connected to form a hexagonal wiring structure. The phase-shifting transformer with a hexagonal wiring structure realizes the change of the phase angle of the two medium-voltage output voltages. The phase-shifting transformer realizes the phase shifting function through the excitation winding and the phase-adjusting winding.

[0006] When the phase-adjusting switch is in the positive tapping position, the phase angle on the medium voltage L2 side lags behind that on the medium voltage L1 side. The phase angle can be reduced by reducing the number of turns of the phase-adjusting winding, and can be increased by increasing the number of turns of the phase-adjusting winding.

[0007] When the phase-modulating switch is in negative tapping, the phase angle on the medium voltage L2 side is ahead of that on the medium voltage L1 side. Changing the number of turns of the phase-modulating winding can also change the size of the phase angle.

[0008] The autotransformer body comprises an autotransformer core, a low-voltage winding, a medium-voltage winding, a high-voltage winding and a voltage regulating winding. The windings of the autotransformer are connected separately according to the connection groups; the high-voltage side 220kV of the autotransformer is a constant, the medium-voltage line end 110kV is on-load voltage regulation, the voltage regulating switch is positive and negative regulation, when the voltage regulating switch is in the positive tap with the maximum number of turns, when the voltage regulating turns are the maximum, the medium voltage voltage is the maximum, and the current is the minimum; when the voltage regulating switch is in the negative tap with the maximum number of turns, the medium voltage voltage is the minimum, and the current is the maximum.

[0009] The autotransformer body and the phase-shifting transformer body are placed in the same transformer oil tank, which can save the space of the transformer. The transformer of the present invention can both adjust the voltage and change the phase angle, and can effectively control the voltage amplitude and phase angle on the medium voltage side, and the voltage amplitude and phase angle can be adjusted separately (decoupled). When the phase-shifting transformer is at zero phase-shifting angle, there is still enough impedance to meet the product's anti-short-circuit capability requirements, and no reactor needs to be connected in series.

[0010] The heights of the autotransformer body and the phase-shifting transformer body are inconsistent; the body with a lower height adopts a double-layer support plate structure, the lower support plate of the double-layer support plate structure fixes the iron core sheet clamp of the body, and the height of the upper support plate matches the height of the other body; the two bodies are fixed to the transformer oil tank by adjusting the height of the upper support plate.

[0011] The autotransformer body and the phase-shifting transformer body are arranged in a T-shape in the transformer oil tank, that is, the middle line of the three-phase bodies of the autotransformer body arranged in a row is perpendicular to the middle line of the three-phase bodies of the phase-shifting transformer body arranged in a row.

[0012] The ends of the three-phase windings of the phase-shifting transformer are connected to form a hexagonal wiring structure. The ends of the three-phase windings of the phase-shifting transformer are connected by connecting wires, and the three-phase windings and the three connecting wires are spaced apart to form a hexagon.

[0013] A manufacturing method of a double-body 220kV step-down phase-shifting transformer, which adds a phase-shifting function to an ordinary 220kV three-phase auto-coupling on-load transformer; it comprises an auto-coupling unit and a phase-shifting unit, the auto-coupling unit is called an auto-coupling transformer, the phase-shifting unit is called a phase-shifting transformer, the auto-coupling unit and the phase-shifting unit are two bodies, namely, an auto-coupling transformer body and a phase-shifting transformer body, and the two bodies are placed in the same transformer oil tank; the 220kV high voltage of the auto-coupling transformer is connected to the 220kV transmission line, and the 110kV medium voltage of the auto-coupling transformer is divided into two paths, one is the medium voltage L1, which does not have the phase-shifting function, only transforms the voltage but does not shift the phase, which is the same as the ordinary auto-coupling transformer; the other is the medium voltage L2, which has the phase-shifting function, and is closed-loop with the 110kV medium voltage of other power grids, the phase is continuously adjustable, and the interconnection line current is continuously controllable. It solves the demand for continuous controllable current of the branch, and also has the function of closing the loop to meet the demand for non-stop power transfer of loads during line maintenance and after-maintenance, thereby improving the reliability of power supply of the power grid.

[0014] The autotransformer body and the phase-shifting transformer body are arranged in a T shape in the transformer oil tank, the voltage regulating switch of the autotransformer is arranged next to the autotransformer, and the phase-adjusting switch of the phase-shifting transformer is arranged next to the phase-shifting transformer; the autotransformer body and the phase-shifting transformer body are placed in separate boxes, and the connection between the autotransformer and the phase-shifting transformer is placed in the box and then connected. This operation is simple and convenient for wiring. At the same time, each body is placed in a separate box to reduce the problem of unstable center of gravity of the body; the 110kV medium voltage of the phase-shifting transformer is connected to another 110kV line, which can both change voltage and shift phase, and can be looped with other power grids to achieve controllable current of the interconnection line.

[0015] Due to impedance reasons, it is impossible to ensure that the heights of the autotransformer body and the phase-shifting transformer body are consistent; the body with a low height adopts a double-layer support plate structure, the lower support plate of the double-layer support plate structure fixes the iron core sheet clamp of the body, and the height of the upper support plate matches the height of the other body; by adjusting the height of the upper support plate, the two bodies are fixed to the transformer oil tank, ensuring that the transformer is reliably fixed and operates reliably.

[0016] The double-body 220kV step-down phase-shifting transformer comprises an autotransformer body, a phase-shifting transformer body, three voltage regulating switches, three phase-adjusting switches, three high-voltage bushings, a high-voltage neutral point bushing, six medium-voltage bushings, three low-voltage bushings, a transformer oil tank, an oil storage cabinet and a cooling device; the 220kV high-voltage outlet three-phase bushings of the double-body 220kV step-down phase-shifting transformer are respectively high-voltage bushing SA, high-voltage bushing SB and high-voltage bushing SC, and the 110kV medium voltage is divided into two paths, the three-phase bushings of the medium voltage L1 are respectively medium-voltage bushing LA1, medium-voltage bushing LB1 and medium-voltage bushing LC1, and the three-phase bushings of the medium voltage L2 are respectively medium-voltage bushing LA2, medium-voltage bushing LB2 and medium-voltage bushing LC2; the three-phase low-voltage bushings are respectively low-voltage bushing a, low-voltage bushing b and low-voltage bushing c, and the high-voltage neutral point is the high-voltage neutral point bushing O.

[0017] The oil conservator is installed on the top of the transformer oil tank and is connected to the transformer oil tank. When the oil in the transformer oil tank expands with the increase of temperature, the excess oil reaches the oil conservator through the connecting pipe, so that the oil conservator completes the function of storing transformer oil. Conversely, when the temperature drops, the oil in the oil conservator reaches the transformer oil tank (or switch oil chamber) through the connecting pipe to supplement the shortage of transformer oil.

[0018] The manifold of the cooling device adopts a modular structure and is arranged in units of four or six groups of plate-type radiators, and can be installed in groups, which is convenient for operation and saves transformer installation time.

[0019] The positive effects of the present invention are as follows: a phase shifting function is added to an ordinary 220kV three-phase auto-coupling on-load transformer, and the phase is continuously adjustable, which solves the demand for continuous control of branch currents; it can not only solve the problem of double busbar parallel connection, but also has the function of loop closing, which meets the demand for non-stop power supply when the line is under maintenance and put into use after maintenance, improves the reliability and safety of power supply of the power grid, meets the development requirements of the intelligent distribution network, and has good social benefits and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the wiring of the embodiment of the present invention and the system; Figure 2 is a wiring schematic diagram of an embodiment of the present invention; Figure 3 This is a schematic diagram of the bushing outlet according to an embodiment of the present invention; Figure 4 Schematic diagram of an autotransformer body and a voltage regulating switch and a schematic diagram of a phase-shifting transformer body and a phase-adjusting switch according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the fixing structure of the double-layer support plate of the body of the embodiment of the present invention; Figure 6 is an overall layout diagram of an embodiment of the present invention; In the figure: autotransformer body 1, phase-shifting transformer body 2, voltage regulating switch 3, phase-adjusting switch 4, high-voltage bushing 5, high-voltage neutral point bushing 6, medium-voltage bushing 7, low-voltage bushing 8, transformer oil tank 9, oil storage cabinet 10, cooling device 11, upper support plate 12, and lower support plate 13. DETAILED DESCRIPTION

[0021] The present invention will be further described below through embodiments in conjunction with the accompanying drawings.

[0022] A double-body 220kV step-down phase-shifting transformer comprises an autocoupler unit and a phase-shifting unit, wherein the autocoupler unit is called an autotransformer, and the phase-shifting unit is called a phase-shifting transformer. The autocoupler unit and the phase-shifting unit are two bodies, namely an autotransformer body 1 and a phase-shifting transformer body 2, and the two bodies are placed in the same transformer oil tank 9; the voltage regulating switch 3 of the autotransformer is arranged next to the autotransformer, and the phase-adjusting switch 4 of the phase-shifting transformer is arranged next to the phase-shifting transformer; the 220kV high voltage of the autotransformer is connected to a 220kV transmission line, and the 110kV medium voltage of the autotransformer is divided into two paths, one of which is a medium voltage L1 without a phase-shifting function, and only transforms the voltage without phase-shifting, which is the same as an ordinary autotransformer; the other of which is a medium voltage L2 with a phase-shifting function, and is looped with the 110kV medium voltage of other power grids, with a continuously adjustable phase and a continuously controllable flow of the interconnecting line.

[0023] The phase-shifting transformer body includes a phase-shifting transformer core, an excitation winding and a phase-adjusting winding. The ends of the three-phase windings of the phase-shifting transformer are connected to form a hexagonal wiring structure. The phase-shifting transformer with a hexagonal wiring structure realizes the change of the phase angle of the two medium-voltage output voltages. The phase-shifting transformer realizes the phase-shifting function through the excitation winding and the phase-adjusting winding. When the phase-adjusting switch 4 is in a positive tap, the phase angle on the medium-voltage L2 side lags behind the medium-voltage L1 side. By reducing the number of turns of the phase-adjusting winding, the size of the phase angle can be reduced, and by increasing the number of turns of the phase-adjusting winding, the size of the phase angle can be increased. When the phase-adjusting switch 4 is in a negative tap, the phase angle on the medium-voltage L2 side is ahead of the medium-voltage L1 side. Changing the number of turns of the phase-adjusting winding can also change the size of the phase angle. The 110kV medium voltage of the phase-shifting transformer is connected to another 110kV line. This line can both transform and shift phases, and can be looped with other power grids to realize controllable current of the interconnecting line.

[0024] The autotransformer body 1 comprises an autotransformer core, a low voltage winding, a medium voltage winding, a high voltage winding and a voltage regulating winding, and the windings of the autotransformer are connected respectively according to the connection groups; the high voltage side 220kV of the autotransformer is a constant, the medium voltage line end 110kV is on-load voltage regulation, the voltage regulating switch 3 is positive and negative regulation, when the voltage regulating switch 3 is in the positive tap with the maximum number of turns, when the voltage regulating turns are the maximum, the medium voltage voltage is the maximum, and the current is the minimum; when the voltage regulating switch 3 is in the negative tap with the maximum number of turns, the medium voltage voltage is the minimum, and the current is the maximum.

[0025] The autotransformer body and the phase-shifting transformer body are placed in the same transformer oil tank, which can save the space of the transformer. The transformer of the present invention can both adjust the voltage and change the phase angle, and can effectively control the voltage amplitude and phase angle on the medium voltage side, and the voltage amplitude and phase angle can be adjusted separately (decoupled). When the phase-shifting transformer is at zero phase-shifting angle, there is still enough impedance to meet the product's anti-short-circuit capability requirements, and no reactor needs to be connected in series.

[0026] The autotransformer body 1 and the phase-shifting transformer body 2 are of different heights; the body with a lower height adopts a double-layer support plate structure, the lower support plate 13 of the double-layer support plate structure fixes the core sheet clamp of the body, and the height of the upper support plate 12 matches the height of the other body; the two bodies are fixed to the transformer oil tank by adjusting the height of the upper support plate.

[0027] A manufacturing method of a double-body 220kV step-down phase-shifting transformer, which adds a phase-shifting function to an ordinary 220kV three-phase auto-coupling on-load transformer; the transformer comprises an autocoupling unit and a phase-shifting unit, wherein the autocoupling unit is called an autotransformer, and the phase-shifting unit is called a phase-shifting transformer. The autocoupling unit and the phase-shifting unit are two bodies, namely, an autotransformer body 1 and a phase-shifting transformer body 2, and the two bodies are placed in the same transformer oil tank 9; the 220kV high voltage of the autotransformer is connected to a 220kV transmission line, and the 110kV medium voltage of the autotransformer is divided into two paths, one of which is a medium voltage L1, which does not have a phase-shifting function and only transforms the voltage without phase-shifting, just like an ordinary autotransformer; the other of which is a medium voltage L2, which has a phase-shifting function and is looped with other 110kV medium voltage power grids, with a continuously adjustable phase and a continuously controllable interconnection line flow. It not only meets the demand for continuous control of the branch current, but also has the function of loop closing to meet the demand for non-stop power supply when the line is under maintenance or put into operation after maintenance, thereby improving the reliability of power supply of the power grid.

[0028] The autotransformer body 1 and the phase-shifting transformer body 2 are arranged in a T shape in the transformer oil tank, the voltage regulating switch of the autotransformer is arranged next to the autotransformer, and the phase-adjusting switch of the phase-shifting transformer is arranged next to the phase-shifting transformer; the autotransformer body 1 and the phase-shifting transformer body 2 are placed in separate boxes, and the connection between the autotransformer and the phase-shifting transformer is placed in the box and then connected. This operation is simple and the wiring is convenient. At the same time, placing each body in a separate box can reduce the problem of unstable center of gravity of the body.

[0029] Due to impedance reasons, it is impossible to ensure that the heights of the autotransformer body 1 and the phase-shifting transformer body 2 are consistent; the body with a low height adopts a double-layer support plate structure, and the lower support plate 13 of the double-layer support plate structure fixes the iron core sheet clamp of the body, and the height of the upper support plate 12 matches the height of the other body; by adjusting the height of the upper support plate, the two bodies are fixed to the transformer oil tank, ensuring that the transformer is reliably fixed and operates reliably.

[0030] The double-body 220kV step-down phase-shifting transformer comprises an autotransformer body 1, a phase-shifting transformer body 2, three voltage regulating switches, three phase-adjusting switches, three high-voltage bushings 5, a high-voltage neutral point bushing 6, six medium-voltage bushings 7, three low-voltage bushings 8, a transformer oil tank 9, an oil storage cabinet 10 and a cooling device 11; the 220kV high-voltage outlet three-phase bushings of the double-body 220kV step-down phase-shifting transformer are respectively high-voltage bushing SA, high-voltage bushing SB and high-voltage bushing SC, and the 110kV medium voltage is divided into two paths, the three-phase bushings of the medium voltage L1 are respectively medium-voltage bushing LA1, medium-voltage bushing LB1 and medium-voltage bushing LC1, and the three-phase bushings of the medium voltage L2 are respectively medium-voltage bushing LA2, medium-voltage bushing LB2 and medium-voltage bushing LC2; the three-phase low-voltage bushings are respectively low-voltage bushing a, low-voltage bushing b and low-voltage bushing c, and the high-voltage neutral point is the high-voltage neutral point bushing O.

[0031] The oil conservator 10 is installed on the top of the transformer oil tank 9 and is connected to the transformer oil tank. When the oil in the transformer oil tank expands with the increase of temperature, the excess oil reaches the oil conservator through the connecting pipe, so that the oil conservator completes the function of storing transformer oil. On the contrary, when the temperature drops, the oil in the oil conservator reaches the oil tank (or switch oil chamber) through the connecting pipe to supplement the shortage of transformer oil.

[0032] The manifold of the cooling device adopts a modular structure and is arranged in units of four or six groups of plate-type radiators, and can be installed in groups, which is convenient for operation and saves transformer installation time.

Claims

1. A double-body 220kV step-down phase-shifting transformer, characterized in that: The invention comprises an autocoupler unit and a phase shift unit, wherein the autocoupler unit is called an autotransformer and the phase shifter unit is called a phase shifter. The autocoupler unit and the phase shifter unit are two bodies, namely an autotransformer body (1) and a phase shifter body (2), and the two bodies are placed in the same transformer oil tank (9); the voltage regulating switch (3) of the autotransformer is arranged next to the autotransformer, and the phase regulating switch (4) of the phase shifter is arranged next to the phase shifter; the 220 kV high voltage of the autotransformer is connected to a 220 kV transmission line, and the 110 kV medium voltage of the autotransformer is divided into two paths, one of which is a medium voltage L1 without a phase shifting function, and only transforms the voltage without phase shifting, which is the same as an ordinary autotransformer; and the other of which is a medium voltage L2 with a phase shifting function, which is connected to the 110 kV medium voltage of other power grids, and the phase is continuously adjustable, and the flow of the interconnection line is continuously controllable.

2. A double-body 220kV step-down phase-shifting transformer according to claim 1, characterized in that: The phase-shifting transformer body includes a phase-shifting transformer core, an excitation winding and a phase-adjusting winding. The ends of the three-phase windings of the phase-shifting transformer are connected to form a hexagonal wiring structure. The phase-shifting transformer with a hexagonal wiring structure realizes the change of the phase angle of the two medium-voltage output voltages. The phase-shifting transformer realizes the phase shifting function through the excitation winding and the phase-adjusting winding.

3. A double-body 220kV step-down phase-shifting transformer according to claim 1 or 2, characterized in that: When the phase-adjusting switch (4) is in the positive tapping state, the phase angle on the medium voltage L2 side lags behind that on the medium voltage L1 side. The phase angle can be reduced by reducing the number of turns of the phase-adjusting winding, and can be increased by increasing the number of turns of the phase-adjusting winding.

4. A double-body 220kV step-down phase-shifting transformer according to claim 1 or 2, characterized in that: When the phase-adjusting switch (4) is in negative tapping, the phase angle on the medium voltage L2 side is ahead of that on the medium voltage L1 side. Changing the number of turns of the phase-adjusting winding can also change the size of the phase angle.

5. A double-body 220kV step-down phase-shifting transformer according to claim 1 or 2, characterized in that: The autotransformer body (1) comprises an autotransformer core, a low-voltage winding, a medium-voltage winding, a high-voltage winding and a voltage regulating winding, and the windings of the autotransformer are connected respectively according to the connection group; the high-voltage side 220kV of the autotransformer is constant, the medium-voltage line end 110kV is on-load voltage regulation, the voltage regulating switch (3) is positive and negative regulation, when the voltage regulating switch (3) is in the positive tap with the maximum number of turns, when the voltage regulating turns are the maximum, the medium voltage voltage is the maximum, and the current is the minimum; when the voltage regulating switch (3) is in the negative tap with the maximum number of turns, the medium voltage voltage is the minimum, and the current is the maximum.

6. A double-body 220kV step-down phase-shifting transformer according to claim 1 or 2, characterized in that: The autotransformer body (1) and the phase-shifting transformer body (2) are of different heights; the body with a lower height adopts a double-layer support plate structure, the lower support plate (13) of the double-layer support plate structure fixes the core sheet clamp of the body, and the height of the upper support plate (12) matches the height of the other body; the two bodies are fixed to the transformer oil tank by adjusting the height of the upper support plate.

7. A double-body 220kV step-down phase-shifting transformer according to claim 1 or 2, characterized in that: The autotransformer body and the phase-shifting transformer body are arranged in a T-shape in the transformer oil tank, that is, the middle line of the three-phase bodies of the autotransformer body arranged in a row is perpendicular to the middle line of the three-phase bodies of the phase-shifting transformer body arranged in a row.

8. A double-body 220kV step-down phase-shifting transformer according to claim 2, characterized in that: The ends of the three-phase windings of the phase-shifting transformer are connected to form a hexagonal wiring structure. The ends of the three-phase windings of the phase-shifting transformer are connected by connecting wires, and the three-phase windings and the three connecting wires are spaced apart to form a hexagon.

9. A method for manufacturing a double-body 220kV step-down phase-shifting transformer according to any one of claims 1 to 8, characterized in that: A phase shifting function is added to an ordinary 220kV three-phase auto-coupling on-load transformer; the auto-coupling unit and the phase shifting unit are two bodies, namely, an auto-coupling transformer body (1) and a phase shifting transformer body (2), and the two bodies are placed in the same transformer oil tank (9); the 220kV high voltage of the auto-coupling transformer is connected to a 220kV transmission line, and the 110kV medium voltage of the auto-coupling transformer is divided into two paths, one of which is a medium voltage L1 without a phase shifting function, and only transforms the voltage without phase shifting, which is the same as an ordinary auto-coupling transformer; the other is a medium voltage L2 with a phase shifting function, which is connected to the 110kV medium voltage of other power grids, and the phase is continuously adjustable, and the interconnection line flow is continuously controllable.

10. A method for manufacturing a double-body 220kV step-down phase-shifting transformer according to claim 9, characterized in that: The autotransformer body (1) and the phase-shifting transformer body (2) are arranged in a T-shape in the transformer oil tank, the voltage regulating switch of the autotransformer is arranged next to the autotransformer, and the phase-shifting switch of the phase-shifting transformer is arranged next to the phase-shifting transformer; the autotransformer body (1) and the phase-shifting transformer body (2) are placed in separate boxes, and the connection between the autotransformer and the phase-shifting transformer is placed in the boxes and then connected; the 110 kV medium voltage of the phase-shifting transformer is connected to another 110 kV line, which can both change the voltage and shift the phase, and can be looped with other power grids to achieve controllable current flow of the interconnection line.

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