Paper-wrapped self-adhesive transposed conductor and three-winding power transformer

Abstract

The utility model discloses a paper-wrapped self-adhesive transposed conductor, which comprises an inner core formed by arranging and combining a plurality of flat conductors and an electrical insulation paper tape wrapped outside the inner core, the plurality of flat conductors are tightly arranged in an array shape, and when a paint film wrapped outside the conductors is heated, the conductors are tightly adhered together to form a firm whole; and the flat wires are consistent in length in the magnetic field. The utility model further discloses a three-winding power transformer which comprises an iron core, a low-voltage coil, a medium-voltage coil and a high-voltage coil, the low-voltage coil, the medium-voltage coil and the high-voltage coil are sequentially wound outwards with the iron core as the center, and the medium-voltage coil is formed by winding the paper-wrapped self-adhesive transposed conductor. The mechanical property, the lodging-resistant strength, the yield limit and other properties of the paper-wrapped self-adhesive transposed conductor are all higher than those of a common conductor; the three-winding power transformer of the medium-voltage coil formed by winding the paper-wrapped self-adhesive transposed conductor has better sudden short circuit resistance mechanical performance, is not easy to damage, has higher current density and is beneficial to saving cost.

Description

Technical Field

[0001] The utility model relates to the technical field related to power transformers, and more precisely to a paper-wrapped self-adhesive transposed conductor and a three-winding power transformer. Background Art

[0002] In order to ensure the safe and stable operation of the power grid, the transformer's short-circuit resistance must be guaranteed. Therefore, it is necessary to improve the transformer structure design and improve the transformer's short-circuit resistance mechanical strength. In order to detect the transformer's short-circuit resistance, a short-circuit test is required. Taking a 110kV three-winding transformer with a capacity of 50000kVA as an example, the cost of random short-circuit testing is as high as 500,000, which is very expensive. Therefore, how to design an effective transformer short-circuit resistance solution is crucial to reducing costs.

[0003] See also Figures 1 to 3 The existing three-winding power transformer includes an iron core 1 and a low-voltage coil 21, a medium-voltage coil 22, and a high-voltage coil 23 which are wound outward in sequence with the iron core 1 as the center. When the three-winding power transformer is short-circuited, the coils are subject to radial force and axial force. The radial force causes the outer coil to be subjected to radial tension, resulting in permanent deformation of the coil, insulation cracking, and even wire breakage, causing inter-turn short circuits and coil burning. The radial force causes the inner coil to be subjected to radial pressure, resulting in instability, bending, and wire tilting of the inner coil. The axial force causes the wire to bend axially and vibrate axially, resulting in loosening, torsional shedding, or collapse between the wire and the axial oil channel gasket. Figures 1 to 3 Under the three working conditions, the medium voltage coil 22 must not only withstand the radial pressure when it is used as an inner coil in the first working condition, but also withstand the radial tension when it is used as an outer coil in working condition 3. The high voltage coil 23 and the low voltage coil 21 only need to withstand radial tension and radial pressure respectively in the three working conditions. If the medium voltage coil 22 is a coil wound with ordinary wires, due to the poor mechanical properties of ordinary wires, easy instability, insufficient friction between turns, poor anti-lodging strength, low yield limit and other factors, if it encounters various sudden short circuits during operation, the above accidents are very likely to occur.

[0004] In order to ensure the short-circuit resistance and structural strength of the three-winding power transformer, it is necessary to overcome the above problems caused by the coil structure. The current solution includes reducing the current density to reduce the short-circuit current multiple and thus reduce the short-circuit mechanical force, but the reduction in current density brings a large increase in the cost of the wire; the current solution also includes increasing the support and clamping force of the wire through process measures, but it will cause the transformer structure to become complicated and non-universal, the operation is more complicated, the production cycle is long and the effect is not good. Utility Model Content

[0005] In view of this, the purpose of the utility model is to provide a paper-wrapped self-adhesive transposed conductor to replace the existing ordinary conductors and improve the structural strength.

[0006] Another object of the utility model is to provide a three-winding power transformer, which adopts the paper-wrapped self-adhesive transposed conductor to form a medium-voltage coil.

[0007] In order to achieve the above-mentioned purpose, the utility model provides a paper-wrapped self-adhesive transposed conductor, comprising an inner core formed by arranging and combining a plurality of flat conductors and an electrical insulating paper tape wrapped around the outer portion of the inner core, wherein the plurality of flat conductors are closely arranged in an array, adjacent flat conductors are fixedly connected, and each of the flat conductors has the same length in a magnetic field.

[0008] Preferably, the flat wire comprises a wire core and an acetal paint film wrapped around the wire core, the acetal paint films of adjacent flat wires are in contact with each other, and when heated, the flat wires are bonded to each other to form an integrated solidified structure.

[0009] Preferably, 29 flat wires are included, 28 of which are arranged in two rows, and the remaining flat wire is arranged in a single row at the end.

[0010] The utility model provides a three-winding power transformer, comprising an iron core and a low-voltage coil, a medium-voltage coil and a high-voltage coil which are sequentially wound outward with the iron core as the center, wherein the medium-voltage coil is formed by winding a paper-wrapped self-adhesive transposed conductor.

[0011] Compared with the prior art, the advantages of a paper-wrapped self-adhesive transposed conductor and a three-winding power transformer disclosed by the utility model are: the mechanical properties, lodging resistance, yield limit and other properties of the paper-wrapped self-adhesive transposed conductor are stronger than those of ordinary conductors; the medium-voltage coil formed by winding the paper-wrapped self-adhesive transposed conductor has better structural strength and has good ability to resist sudden short-circuit mechanical forces; the three-winding power transformer using the medium-voltage coil formed by winding the paper-wrapped self-adhesive transposed conductor has better mechanical properties against sudden short circuits, is not easy to be damaged, and has a higher current density, which helps to save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] like Figure 1 The figure shows the stress diagram of the coil of the three-winding power transformer in the prior art under the first working condition.

[0014] like Figure 2The figure shows the stress diagram of the coil of the three-winding power transformer in the prior art under the second working condition.

[0015] like Figure 3 The figure shows the stress diagram of the coil of the prior art three-winding power transformer under the third working condition.

[0016] like Figure 4 Shown is a cross-sectional view of a paper-wrapped self-adhesive transposed conductor of the utility model. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0018] like Figure 4 As shown, a paper-wrapped self-adhesive transposed conductor 3 of the present application includes an inner core formed by arranging and combining a plurality of flat conductors 31 and an electrical insulating paper tape 32 wrapped around the inner core, wherein the plurality of flat conductors 31 are closely arranged in an array, adjacent flat conductors 31 are fixedly connected, and each flat conductor 31 has the same length in the magnetic field. The paper-wrapped self-adhesive transposed conductor 3 has a higher current density and structural strength, and the conductor eddy current loss is small.

[0019] The flat conductor 31 includes a conductor core 311 and an acetal paint film 312 wrapped around the conductor core 311, and the acetal paint films 312 of adjacent flat conductors 31 are in contact with each other. The inner core of the paper-wrapped self-adhesive transposed conductor 3 is dried after being wound with the electrical insulating paper tape 32, and the acetal paint films 312 of adjacent flat conductors 31 are tightly bonded together after being heated to form a solid overall structure, thereby improving the mechanical properties, lodging resistance, yield limit and other properties of the paper-wrapped self-adhesive transposed conductor 3.

[0020] Preferably, the paper-wrapped self-adhesive transposed conductor 3 includes 29 flat conductors 31, of which 28 flat conductors 31 are arranged in two rows, and the remaining flat conductor 31 is arranged in a single row at the end. The lengths of the two sides of the cross section of the flat conductor 31 are 1.3 mm and 6.2 mm, and the thickness of the electrical insulating paper tape 32 is 0.6 mm.

[0021] The present application also provides a three-winding power transformer, comprising an iron core and a low-voltage coil, a medium-voltage coil, and a high-voltage coil wound outward in sequence with the iron core as the center, wherein the medium-voltage coil is formed by winding the paper-wrapped self-adhesive transposed conductor 3.

[0022] The following is an analysis of the effect of the average annular stress of the paper-wrapped self-adhesive transposed conductor 3 described in the present application. The average annular stress is an important stress to ensure that the coil does not lose radial stability. It is an average annular tensile stress for the outer coil and an average annular compressive stress for the inner coil. Ordinary wires are used as a control. The ordinary wires have a 9x1.7mm core, and the core is wrapped with a 0.45mm thick insulating paper tape.

[0023] According to the national standard GB1094.5 "Power transformer part 5: ability to withstand short circuit":

[0024] The average annular stress is: σ=Fr / (2π*Acu)

[0025] Average annular tensile stress: σ1≤0.9Rp0.2;

[0026] Average annular compressive stress: ordinary wire σ2≤0.35Rp0.2;

[0027] Self-adhesive transposed conductor σ2≤0.6Rp0.2;

[0028] σ1——Average annular tensile stress, N / mm2

[0029] σ2——Average annular compressive stress, N / mm2

[0030] Fr——Radial force, N (simulated calculation of this transformer compression stress = 56000N, tensile stress = 147000N)

[0031] Acu———conductor cross-sectional area, mm2

[0032] Rp0.2——The yield limit is the stress when the permanent deformation is 0.2%, MPa

[0033] (Ordinary conductor: 100MPa, paper-wrapped self-adhesive transposed conductor: 220MPa)

[0034] The medium voltage coil of the transformer in this example uses 29 paper-wrapped self-adhesive transposed conductors, which are wound continuously.

[0035] Wire gauge: HRNC3-0.6 1.3x6.2x(29) / 22.5x13.24, 1 wire in parallel, wire cross-sectional area 234mm2

[0036] (If ordinary wires are used, the wire gauge is: ZB-0.45 1.7x9 / 2.15x9.45, 16 wires in parallel, and the wire cross-sectional area is 239mm2)

[0037] When in Figure 1 In the first working condition shown: the average annular compressive stress of the medium voltage coil as the inner coil:

[0038] σ2=Fr / (2π*Acu)=56000 / (2π*234)=38.1MPa;

[0039] This value is larger than 0.35Rp0.2=35MPa of ordinary wires and smaller than 0.6Rp0.2=132MPa of self-adhesive composite wires, so the self-adhesive composite wires meet the requirements while ordinary wires do not.

[0040] When in Figure 2 In the second working condition shown: the average annular tensile stress of the medium voltage coil as the outer coil:

[0041] σ1=Fr / (2π*Acu)=147000 / (2π*234)=100MPa;

[0042] This value is larger than 0.9Rp0.2=90MPa of ordinary wires and smaller than 0.9Rp0.2=198MPa of self-adhesive composite wires, so the self-adhesive composite wires meet the requirements while ordinary wires do not.

[0043] Here, only the main stress, namely the average annular stress, is calculated and evaluated. The results reflected in this stress verification using different conductors can better reflect the differences between different conductors. From the above results, it can be seen that the medium-voltage coil using the paper-wrapped self-adhesive transposed conductor has passed the verification. Compared with the ordinary conductor structure, this structure can achieve a higher current density and save considerable costs. At the same time, the overall structure is simple and reliable, has strong versatility, and is easy to produce.

[0044] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A paper-wrapped self-adhesive transposed conductor, characterized in that: It includes an inner core formed by arranging and combining a plurality of flat wires and an electrical insulating paper tape wrapped around the inner core. The plurality of flat wires are closely arranged in an array, adjacent flat wires are fixedly connected, and each flat wire has the same length in the magnetic field.

2. The paper-wrapped self-adhesive transposed conductor according to claim 1, characterized in that: The flat wire comprises a wire core and an acetal paint film wrapped around the wire core. The acetal paint films of adjacent flat wires are in contact with each other. When heated, the flat wires are bonded to each other to form an integrated solidified structure.

3. The paper-wrapped self-adhesive transposed conductor according to claim 1, characterized in that: The invention comprises 29 flat wires, 28 of which are arranged in two rows, and the remaining flat wire is arranged in a single row at the end.

4. A three-winding power transformer, characterized in that: It comprises an iron core and a low-voltage coil, a medium-voltage coil and a high-voltage coil which are wound outward in sequence with the iron core as the center, wherein the medium-voltage coil is formed by winding the paper-wrapped self-adhesive transposed conductor according to any one of claims 1-3.

Images