CN220138085U - Three-phase double-winding transformer inlet wire arrangement structure - Google Patents

Abstract

The utility model provides a three-phase double-winding transformer incoming line arrangement structure, which comprises: the transformer, the transformer framework, the first hanging wire, the second hanging wire, the first lead wire, the second lead wire, the third lead wire and the low-voltage side line inlet equipment. The high-voltage side of the transformer is electrically connected with a high-voltage side power distribution device through the first lead; the transformer framework is connected with the first lead through the first hanging wire; the low-voltage side of the transformer is electrically connected with the low-voltage side input device through the third lead; the transformer framework is connected with a low-voltage side power distribution device through the second hanging wire; the low-voltage side line inlet device is electrically connected with the second hanging line through the second lead; the first lead is a single-loop three-phase lead; the third lead is a double-circuit three-phase lead wire so as to solve the problem that the low-voltage side lead wire equipment is damaged due to overlarge working current of the three-phase double-winding transformer.

Description

Three-phase double-winding transformer inlet wire arrangement structure

Technical Field

The utility model relates to the technical field of power supply, in particular to an incoming line arrangement structure of a three-phase double-winding transformer.

Background

The electric energy output by the generator is boosted by the transformer and then is transmitted to the load center, or is transmitted to other power systems by the interconnecting transformer, then is reduced by the step-down transformer and then is transmitted to an industrial area or a living area, and finally, the voltage is reduced to the application level by the distribution transformer. The transformers are divided according to the number of phases and can be divided into single-phase transformers and three-phase transformers. The transformers are divided according to the number of windings, and can be divided into a double-winding transformer and a three-winding transformer.

To simplify the voltage class of a three-phase system, reducing the repeated step-up and step-down capacity, in some embodiments, a three-phase double-winding transformer is employed. However, when the voltage level of the low-voltage side of the three-phase double-winding transformer is low, the working current is overlarge and exceeds the rated current of the low-voltage side inlet equipment, the probability of damaging the low-voltage side inlet equipment is increased, and potential safety hazards appear.

Disclosure of Invention

The utility model provides a three-phase double-winding transformer incoming line arrangement structure, which aims to solve the problem that low-voltage side incoming line equipment is damaged due to overlarge working current of a three-phase double-winding transformer.

The utility model provides a three-phase double-winding transformer incoming line arrangement structure, which comprises: the transformer, the transformer framework, the first hanging wire, the second hanging wire, the first lead wire, the second lead wire, the third lead wire and the low-voltage side line inlet equipment.

The high-voltage side of the transformer is electrically connected with a high-voltage side power distribution device through the first lead; the transformer framework is connected with the first lead through the first hanging wire; the low-voltage side of the transformer is electrically connected with the low-voltage side input device through the third lead; the transformer framework is connected with a low-voltage side power distribution device through the second hanging wire; the low-voltage side line inlet device is electrically connected with the second hanging line through the second lead; the first lead is a single-loop three-phase lead; and the third lead is a double-circuit three-phase lead.

The first lead wire at the high-voltage side of the transformer is set to be a single-circuit three-phase lead wire, the third lead wire at the low-voltage side of the transformer is split to be a double-circuit three-phase lead wire, and the split three-phase lead wire is connected with the transformer framework according to the safe clear distances between phases and between phases under different voltage levels of the high-voltage side and the low-voltage side, so that the problem that the low-voltage side lead wire equipment is damaged due to overlarge working current of the three-phase double-winding transformer is solved.

Optionally, the low voltage side line inlet device comprises a plurality of gas insulated metal enclosed switches.

The gas-insulated metal-enclosed switch has the advantages of small occupied area, high reliability, flexible configuration, convenient installation, strong safety, strong environment adaptability and small maintenance workload, and is suitable for the low-voltage side line-incoming equipment.

Optionally, the device further comprises a first insulator string and a second insulator string; one end of the first insulator string is connected with the first hanging wire in series; the other end of the first insulator string is connected with the transformer framework; one end of the second insulator string is connected with the second hanging wire in series; the other end of the second insulator string is connected with the transformer framework.

The first and second insulator strings are used to suspend the first and second suspension wires and insulate the first and second suspension wires from the transformer frame and the ground.

Optionally, the top surface of the transformer is a rectangular plane.

The top surface of the transformer is a rectangular plane, so that internal accessories of the transformer can be protected.

Optionally, the transformer further comprises a transformer high-voltage side sleeve and a transformer low-voltage side sleeve; the high-voltage side sleeve and the low-voltage side sleeve of the transformer are arranged on the transformer, and the top end of the high-voltage side sleeve of the transformer is higher than the top surface of the transformer; the top end of the low-voltage side sleeve of the transformer is lower than the top surface of the transformer; the high-voltage side sleeve of the transformer is sleeved with the first lead; and the low-voltage side sleeve of the transformer is sleeved with the third lead. The high-voltage side sleeve of the transformer and the low-voltage side sleeve of the transformer play a role in insulation and fixation.

Optionally, the transformer framework is a gate-type framework; the transformer framework comprises a cross beam and two beam columns; the beam is of a strip-shaped structure, and the beam column is of a V-shaped structure; the beam comprises a first end and a second end, and the first end and the second end of the beam are respectively and fixedly connected with the top ends of the V-shaped structures of the two beam columns; two bottom ends of the V-shaped structure of the beam column are fixedly connected with the ground.

The transformer framework is a door-shaped framework, so that the space height can be fully utilized, the transverse arrangement size of the three-phase double-winding transformer inlet wire arrangement structure is compressed, and the occupied area of the land is reduced.

Optionally, the width of the cross beam is greater than the high voltage side incoming line electrical distance and the width of the cross beam is greater than the low voltage side incoming line electrical distance. The cross beam is facilitated to arrange the first and second suspension wires.

Optionally, the first lead wire comprises a single-circuit phase a lead wire, a single-circuit phase B lead wire and a single-circuit phase C lead wire; the single-circuit phase A incoming line, the single-circuit phase B incoming line and the single-circuit phase C incoming line are sequentially arranged in parallel; the high-voltage side incoming line electrified distance is equal to the phase-to-ground distance between the single-circuit A phase incoming line, the single-circuit B phase incoming line and the single-circuit C phase incoming line, and the sum of the phase-to-ground distance between the single-circuit A phase incoming line and the first end of the cross beam and the phase-to-ground distance between the single-circuit C phase incoming line and the second end of the cross beam.

Optionally, the third lead wire includes a first phase-return-a lead wire, a first phase-return-B lead wire, a first phase-return-C lead wire, a second phase-return-a lead wire, a second phase-return-B lead wire, and a second phase-return-C lead wire; the first phase-returning A phase incoming line, the first phase-returning B phase incoming line, the first phase-returning C phase incoming line, the second phase-returning A phase incoming line, the second phase-returning B phase incoming line and the second phase-returning C phase incoming line are sequentially arranged in parallel.

The low-voltage side incoming line charging distance is equal to the sum of a first distance, a second distance, a third distance, a fourth distance and a fifth distance; the first distance is the phase-to-ground distance between the first return A-phase wire, the first return B-phase wire and the first return C-phase wire, the second distance is the phase-to-ground distance between the second return A-phase wire, the second return B-phase wire and the second return C-phase wire, the third distance is the phase-to-phase distance between the first return C-phase wire and the second return A-phase wire, the fourth distance is the phase-to-ground distance between the first return A-phase wire and the first end of the cross beam, and the fifth distance is the phase-to-ground distance between the second return C-phase wire and the second end of the cross beam.

As can be seen from the above technical solution, the present utility model provides a three-phase double-winding transformer incoming line arrangement structure, comprising: the transformer, the transformer framework, the first hanging wire, the second hanging wire, the first lead wire, the second lead wire, the third lead wire and the low-voltage side line inlet equipment. The high-voltage side of the transformer is electrically connected with a high-voltage side power distribution device through the first lead; the transformer framework is connected with the first lead through the first hanging wire; the low-voltage side of the transformer is electrically connected with the low-voltage side input device through the third lead; the transformer framework is connected with a low-voltage side power distribution device through the second hanging wire; the low-voltage side line inlet device is electrically connected with the second hanging line through the second lead; the first lead is a single-loop three-phase lead; the third lead is a double-circuit three-phase lead wire so as to solve the problem that the low-voltage side lead wire equipment is damaged due to overlarge working current of the three-phase double-winding transformer.

Drawings

In order to more clearly illustrate the technical solution of the present utility model, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic plan view of an incoming line arrangement structure of a three-phase double-winding transformer according to an embodiment of the present utility model;

fig. 2 is a schematic cross-sectional view of an incoming line arrangement structure of a three-phase double-winding transformer according to an embodiment of the present utility model;

fig. 3 is an electrical wiring schematic diagram of a three-phase double-winding transformer inlet wire arrangement structure according to an embodiment of the present utility model.

Illustration of:

the high-voltage side transformer comprises a 1-transformer, a 2-transformer high-voltage side sleeve, a 3-transformer low-voltage side sleeve, a 4-first lead, a 5-second hanging wire, a 6-low-voltage side line feeding device, a 7-transformer framework, an 8-first hanging wire, a 9-third lead, a 10-second lead, an 11-first insulator string and a 12-second insulator string.

Detailed Description

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The embodiments described in the examples below do not represent all embodiments consistent with the utility model. Merely exemplary of systems and methods consistent with aspects of the utility model as set forth in the claims.

The transformer is a device for changing an ac voltage by using the principle of electromagnetic induction, and the main components are a primary coil, a secondary coil and an iron core. The transformers are divided according to the number of phases and can be divided into single-phase transformers and three-phase transformers. The transformers are divided according to the number of windings, and can be divided into a double-winding transformer and a three-winding transformer.

To simplify the voltage class of a three-phase system, reducing the repeated step-up and step-down capacity, in some embodiments, a three-phase double-winding transformer is employed. However, when the voltage level of the low-voltage side of the three-phase double-winding transformer is low, the working current is overlarge and exceeds the rated current of the low-voltage side inlet equipment, the probability of damaging the low-voltage side inlet equipment is increased, and potential safety hazards appear.

In order to solve the problem of damage to low-voltage side line inlet equipment caused by excessive working current of a three-phase double-winding transformer, refer to fig. 1-3, wherein fig. 1 is a schematic plan view of a line inlet arrangement structure of the three-phase double-winding transformer; FIG. 2 is a schematic cross-sectional view of a three-phase double-winding transformer inlet wire arrangement; fig. 3 is an electrical wiring schematic diagram of a three-phase double-winding transformer inlet wire arrangement. The embodiment of the utility model provides a three-phase double-winding transformer incoming line arrangement structure, which comprises the following steps: the transformer 1, the transformer frame 7, the first suspension wire 8, the second suspension wire 5, the first lead 4, the second lead 10, the third lead 9 and the low voltage side inlet device 6.

Wherein the high-voltage side of the transformer 1 is electrically connected with a high-voltage side power distribution device through the first lead 4; the transformer frame 7 is connected with the first lead wire 4 through the first hanging wire 8; the low-voltage side of the transformer 1 is electrically connected to the low-voltage side input device 6 via the third lead 9; the transformer framework 7 is connected with a low-voltage side power distribution device through the second hanging wire 5; the low voltage side line inlet device 6 is electrically connected with the second hanging line 5 through the second lead 10; the first lead 4 is a single-circuit three-phase lead; the third lead 9 is a double-loop three-phase lead.

It should be understood that, since the third lead 9 is a double-loop three-phase lead, the second hanger 5 and the second lead 10 are also double-loop three-phase leads; the first lead 4 is a single-loop three-phase lead, and the first hanging wire 8 is also a single-loop three-phase lead.

In order to further reduce the potential safety hazard, the suspension points of the first suspension wire 8 and the first lead 4 and the suspension points of the second lead 10 and the second suspension wire 5 and the distances between the lines are determined according to the phase-to-phase safety clear distance under different voltage levels of the high voltage side and the low voltage side. For example, when the voltage on the high voltage side is 220kv, the phase-to-ground safe clear distance may be 6 meters, and the lowest phase-to-ground clear distance may be 6 meters or more after the first hanging wire 8 is hung from the first lead wire 4. When the voltage of the high-voltage side is 220kv, the inter-circuit safety distance is 3 meters, and the distance between the circuits is more than or equal to 3 meters.

The first lead 4 at the high-voltage side of the transformer 1 is set as a single-circuit three-phase lead, the third lead 9 at the low-voltage side of the transformer 1 is split and set as a double-circuit three-phase lead, and the split and set as a double-circuit three-phase lead is connected with the transformer framework 7 according to the inter-phase and phase-ground safe clear distances at different voltage levels at the high-voltage side and the low-voltage side, so that the problem that the low-voltage side lead equipment 6 is damaged due to overlarge working current of the three-phase double-winding transformer 1 is solved.

In one embodiment, the high-side rated voltage of the transformer 1 is 345kV, the low-side rated voltage of the transformer 1 is 35kV, and the capacity of the transformer 1 is 360MVA. From the calculation, the operating current on the low voltage side was 6236 amperes. The low-voltage side input device 6 adopts a device with a rated voltage of 35kV, the maximum working current of the low-voltage side input device 6 is 5000 amperes and is smaller than the working current of the low-voltage side, and the low-voltage side input device 6 is damaged and potential safety hazards appear. The third lead 9 therefore needs to be wired with an enlarged unit, i.e. split into two-circuit three-phase leads, so that the operating current of the low-voltage side lead-in device 6 does not exceed the maximum operating current.

In one embodiment, the low side line inlet device 6 comprises a plurality of gas insulated metal enclosed switches.

It should be understood that, as shown in fig. 3, in this embodiment, the gas-insulated metal-enclosed switch is two, and the two-circuit three-phase wires split by the third wire 9 are controlled separately. The gas-insulated metal-enclosed switch is formed by directly connecting elements such as a circuit breaker, an isolating switch, a grounding switch, a lightning arrester, a voltage transformer, a current transformer, a sleeve, a bus and the like together, and completely sealing the components in a grounded metal shell, wherein sulfur hexafluoride gas with certain pressure is filled in the shell to serve as an insulating and arc extinguishing medium.

The gas-insulated metal-enclosed switch has the advantages of small occupied area, high reliability, flexible configuration, convenient installation, strong safety, strong environment adaptability and small maintenance workload, and is suitable for the low-voltage side line inlet equipment 6.

In one embodiment, further comprising a first insulator string 11 and a second insulator string 12; one end of the first insulator string 11 is connected in series with the first hanging wire 8; the other end of the first insulator string 11 is connected with the transformer framework 7; one end of the second insulator string 12 is connected in series with the second hanging wire 5; the other end of the second insulator string 12 is connected to the transformer frame 7.

It should be understood that the first insulator string 11 and the second insulator string 12 refer to an assembly of two or more insulator elements combined together, a flexible suspension wire.

The first and second insulator strings 11 and 12 are used to suspend the first and second suspension wires 8 and 5 and to insulate the first and second suspension wires 8 and 5 from the transformer frame 7 and the ground.

In one embodiment, the top surface of the transformer 1 is a rectangular plane.

The top surface of the transformer 1 is a rectangular plane, so that internal fittings of the transformer 1 can be protected.

In one embodiment, the transformer further comprises a transformer high-voltage side bushing 2 and a transformer low-voltage side bushing 3; the high-voltage side sleeve 2 and the low-voltage side sleeve 3 of the transformer are arranged on the transformer 1, and the top end of the high-voltage side sleeve 2 of the transformer is higher than the top surface of the transformer 1; the top end of the low-voltage side sleeve 3 of the transformer is lower than the top surface of the transformer 1; the high-voltage side sleeve 2 of the transformer is sleeved with the first lead 4; the low-voltage side sleeve 3 of the transformer is sleeved with the third lead 9.

The high-voltage side sleeve 2 of the transformer and the low-voltage side sleeve 3 of the transformer play a role in insulation and fixation, and the high-voltage side sleeve 2 of the transformer insulates the first lead wires 4 and the first lead wires 4 from the outer surface of the transformer 1; the transformer low-voltage side bushing 3 insulates between the third leads 9 and the outer surface of the transformer 1.

In one embodiment, the transformer frame 7 is a gate frame; the transformer frame 7 comprises a cross beam and two beam columns; the beam is of a strip-shaped structure, and the beam column is of a V-shaped structure; the beam comprises a first end and a second end, and the first end and the second end of the beam are respectively and fixedly connected with the top ends of the V-shaped structures of the two beam columns; two bottom ends of the V-shaped structure of the beam column are fixedly connected with the ground.

The transformer framework 7 is a door-shaped framework, so that the space height can be fully utilized, the transverse arrangement size of the three-phase double-winding transformer inlet wire arrangement structure is compressed, and the occupied area of the land is further reduced.

In one embodiment, the width of the beam is greater than the high side incoming line live distance and the width of the beam is greater than the low side incoming line live distance. The cross beam is made convenient for arranging the first hanger wire 8 and the second hanger wire 5.

In one embodiment, the first lead 4 includes a single-loop a phase lead, a single-loop B phase lead, and a single-loop C phase lead; the single-circuit phase A incoming line, the single-circuit phase B incoming line and the single-circuit phase C incoming line are sequentially arranged in parallel; the high-voltage side incoming line electrified distance is equal to the phase-to-ground distance between the single-circuit A phase incoming line, the single-circuit B phase incoming line and the single-circuit C phase incoming line, and the sum of the phase-to-ground distance between the single-circuit A phase incoming line and the first end of the cross beam and the phase-to-ground distance between the single-circuit C phase incoming line and the second end of the cross beam.

As shown in fig. 1, the phase-to-phase distance between the single-loop a-phase incoming line, the single-loop B-phase incoming line and the single-loop C-phase incoming line is L1, the phase-to-ground distance between the single-loop a-phase incoming line and the first end of the beam is L2, and the phase-to-ground distance between the single-loop C-phase incoming line and the second end of the beam is L2, so that the high-voltage side incoming line has a charging distance equal to 2×l1+2×l2, and the width of the beam should be greater than 2×l1+2×l2, so that the beam is convenient for arranging the first hanging wire 8.

In one embodiment, the third lead 9 includes a first phase-a return lead, a first phase-B return lead, a first phase-C return lead, a second phase-a return lead, a second phase-B return lead, and a second phase-C return lead; the first phase-returning A phase incoming line, the first phase-returning B phase incoming line, the first phase-returning C phase incoming line, the second phase-returning A phase incoming line, the second phase-returning B phase incoming line and the second phase-returning C phase incoming line are sequentially arranged in parallel.

The low-voltage side incoming line charging distance is equal to the sum of a first distance, a second distance, a third distance, a fourth distance and a fifth distance; the first distance is the phase-to-ground distance between the first return A-phase wire, the first return B-phase wire and the first return C-phase wire, the second distance is the phase-to-ground distance between the second return A-phase wire, the second return B-phase wire and the second return C-phase wire, the third distance is the phase-to-phase distance between the first return C-phase wire and the second return A-phase wire, the fourth distance is the phase-to-ground distance between the first return A-phase wire and the first end of the cross beam, and the fifth distance is the phase-to-ground distance between the second return C-phase wire and the second end of the cross beam.

As shown in fig. 1, the phase-to-phase distance between the first phase-to-phase line a, the first phase-to-phase line B and the first phase-to-phase line C is D1, the phase-to-phase distance between the second phase-to-phase line a, the second phase-to-phase line B and the second phase-to-phase line C is D1, the phase-to-phase distance between the first phase-to-phase line C and the second phase-to-phase line a is D3, the distance between the first phase-returning A phase-incoming line and the first end of the cross beam is D2, the distance between the second phase-returning C phase-incoming line and the second end of the cross beam is D2, so that the low-voltage side incoming line has a charging distance equal to 4 xD1+2 xD2+D3, and the width of the cross beam is larger than 4 xD1+2 xD2+D3. The cross beam is made convenient for arranging the second suspension wires 5.

As can be seen from the above technical solutions, the embodiment of the present utility model provides a three-phase double-winding transformer incoming line arrangement structure, including: the transformer 1, the transformer frame 7, the first suspension wire 8, the second suspension wire 5, the first lead 4, the second lead 10, the third lead 9 and the low voltage side inlet device 6. Wherein the high-voltage side of the transformer 1 is electrically connected with a high-voltage side power distribution device through the first lead 4; the transformer frame 7 is connected with the first lead wire 4 through the first hanging wire 8; the low-voltage side of the transformer 1 is electrically connected to the low-voltage side input device 6 via the third lead 9; the transformer framework 7 is connected with a low-voltage side power distribution device through the second hanging wire 5; the low voltage side line inlet device 6 is electrically connected with the second hanging line 5 through the second lead 10; the first lead 4 is a single-circuit three-phase lead; the third lead 9 is a double-circuit three-phase lead wire, so as to solve the problem that the low-voltage side lead wire equipment 6 is damaged due to overlarge working current of the three-phase double-winding transformer.

The above-provided detailed description is merely a few examples under the general inventive concept and does not limit the scope of the present utility model. Any other embodiments which are extended according to the solution of the utility model without inventive effort fall within the scope of protection of the utility model for a person skilled in the art.

Claims (9)

1. A three-phase double-winding transformer inlet wire arrangement, characterized by comprising: a transformer (1), a transformer frame (7), a first hanging wire (8), a second hanging wire (5), a first lead (4), a second lead (10), a third lead (9) and a low voltage side input device (6);

the high-voltage side of the transformer (1) is electrically connected with a high-voltage side power distribution device through the first lead (4); the transformer framework (7) is connected with the first lead (4) through the first hanging wire (8); the low-voltage side of the transformer (1) is electrically connected to the low-voltage side input device (6) via the third lead (9); the transformer framework (7) is connected with a low-voltage side power distribution device through the second hanging wire (5); the low-voltage side input device (6) is electrically connected with the second hanging wire (5) through the second lead wire (10); the first lead (4) is a single-loop three-phase lead; the third lead (9) is a double-circuit three-phase lead.

2. The three-phase double-winding transformer inlet arrangement according to claim 1, characterized in that the low-side inlet device (6) comprises a plurality of gas-insulated metal-enclosed switches.

3. The three-phase double-winding transformer inlet wire arrangement according to claim 1, further comprising a first insulator string (11) and a second insulator string (12); one end of the first insulator string (11) is connected with the first hanging wire (8) in series; the other end of the first insulator string (11) is connected with the transformer framework (7); one end of the second insulator string (12) is connected with the second hanging wire (5) in series; the other end of the second insulator string (12) is connected with the transformer framework (7).

4. The three-phase double-winding transformer inlet wire arrangement according to claim 1, characterized in that the top surface of the transformer (1) is a rectangular plane.

5. The three-phase double-winding transformer inlet wire arrangement according to claim 1, further comprising a transformer high-side bushing (2) and a transformer low-side bushing (3);

the high-voltage side sleeve (2) and the low-voltage side sleeve (3) of the transformer are arranged on the transformer (1), and the top end of the high-voltage side sleeve (2) of the transformer is higher than the top surface of the transformer (1); the top end of the low-voltage side sleeve (3) of the transformer is lower than the top surface of the transformer (1); the high-voltage side sleeve (2) of the transformer is sleeved with the first lead (4); the low-voltage side sleeve (3) of the transformer is sleeved with the third lead (9).

6. The three-phase double-winding transformer inlet wire arrangement according to claim 1, characterized in that the transformer frame (7) is a gate frame; the transformer frame (7) comprises a cross beam and two beams and columns; the beam is of a strip-shaped structure, and the beam column is of a V-shaped structure; the beam comprises a first end and a second end, and the first end and the second end of the beam are respectively and fixedly connected with the top ends of the V-shaped structures of the two beam columns; two bottom ends of the V-shaped structure of the beam column are fixedly connected with the ground.

7. The three-phase double-winding transformer inlet arrangement of claim 6, wherein a width of the cross beam is greater than a high-side inlet charging distance and a width of the cross beam is greater than a low-side inlet charging distance.

8. The three-phase double-winding transformer inlet arrangement according to claim 7, characterized in that the first lead (4) comprises a single-return a-phase inlet, a single-return B-phase inlet and a single-return C-phase inlet; the single-circuit phase A incoming line, the single-circuit phase B incoming line and the single-circuit phase C incoming line are sequentially arranged in parallel; the high-voltage side incoming line electrified distance is equal to the phase-to-ground distance between the single-circuit A phase incoming line, the single-circuit B phase incoming line and the single-circuit C phase incoming line, and the sum of the phase-to-ground distance between the single-circuit A phase incoming line and the first end of the cross beam and the phase-to-ground distance between the single-circuit C phase incoming line and the second end of the cross beam.

9. The three-phase double-winding transformer inlet arrangement according to claim 1, characterized in that the third lead (9) comprises a first return a-phase inlet, a first return B-phase inlet, a first return C-phase inlet, a second return a-phase inlet, a second return B-phase inlet and a second return C-phase inlet; the first phase-returning A incoming line, the first phase-returning B incoming line, the first phase-returning C incoming line, the second phase-returning A incoming line, the second phase-returning B incoming line and the second phase-returning C incoming line are sequentially arranged in parallel;

the low-voltage side incoming line charging distance is equal to the sum of a first distance, a second distance, a third distance, a fourth distance and a fifth distance; the first distance is the phase-to-ground distance between the first return A-phase wire, the first return B-phase wire and the first return C-phase wire, the second distance is the phase-to-ground distance between the second return A-phase wire, the second return B-phase wire and the second return C-phase wire, the third distance is the phase-to-phase distance between the first return C-phase wire and the second return A-phase wire, the fourth distance is the phase-to-ground distance between the first return A-phase wire and the first end of the cross beam, and the fifth distance is the phase-to-ground distance between the second return C-phase wire and the second end of the cross beam.