CA2495382C

CA2495382C - Winding arrangement

Info

Publication number: CA2495382C
Application number: CA2495382A
Authority: CA
Inventors: Peter Heinzig; Jens Hoppe; Dietmar Jahnel
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2002-08-16
Filing date: 2003-07-30
Publication date: 2012-10-23
Anticipated expiration: 2023-07-30
Also published as: BRPI0313483B1; AU2003264248A1; EP1529296A1; CA2495382A1; CN1672226A; HK1080211A1; WO2004019351A1; HK1080211B; BR0313483A; CN1331171C; DE10238521A1; DE10238521B4; EP1529296B1

Abstract

The invention relates to a winding arrangement having a high electric strength. The winding arrangement has at least two juxtaposed windings (34, 37) arranged in a row, said windings being surrounded by a barrier arrangement (38, 40) configured with insulating material. A tubular electric shield (62, 63; 64, 65) is provided in the area of both front faces of the winding (5, 6; 7, 8; 58, 59; 60, 61) of at least one of said windings (1, 3, 4), said shield coaxially surrounding the corresponding winding (1, 2; 3, 4; 37) while leaving an intermediate gap (23A, 63A) and extending axially outward over the corresponding front face of the winding (5, 6; 7, 8; 58, 59; 60, 61) in such a way that its axial height (B) relative to the corresponding front face of the winding (58, 59) is the same or greater than half of the radial width (A) of the intermediate gap (23A, 63A).

Description

WINDING ARRANGEMENT
FIELD OF INVENTION

The invention relates to a winding arrangement having at least two windings which are arranged next to one another in a row. US patent specification 4,318,066 has disclosed a transformer winding which is coaxially surrounded by a tubular, electrostatic shield. The shield extends over the entire axial length of the winding and ends with the two winding end sides. Three further tubular shields, which surround the winding, which decrease in their axial length in stepped fashion from the outside inwards and all of which end with the upper winding end side of the winding, are also provided between the winding and the electrostatic shield. The connection of the winding is also provided there. The electrostatic shields which vary in their length are provided for the purpose of achieving a uniform voltage distribution along the winding when a pulsed voltage is applied to the winding; in this case, the electrostatic shields act as capacitors for dissipating the voltage.

BACKGROUND OF INVENTION

Winding arrangements having at least two windings which are arranged next to one another in a row, as are provided, for example, for inductors, may have, for example, a corresponding core, each of the windings surrounding a limb of the core, and each limb being connected magnetically outside the windings by the core yoke to form a closed circuit. It is also conventional to accommodate such a winding arrangement in a tank formed by conductive walls and to fill the tank with an insulating medium, for example cooling oil.

Such winding arrangements may also be provided for transformers, each of the two windings forming in each case a transformer winding of a respective transformer winding combination. The transformer windings formed by the windings are in this case each associated with a phase and an electrical side, for example the primary side of the transformer, each of the transformer winding combinations having a second transformer winding which forms the other electrical side of the corresponding phase.

In particular in the case of an application of the winding arrangement in an inductor or a transformer for high-voltage DC transmission applications (HVDC
transmission), not only an electrical AC voltage which is subject to harmonics but also a DC
voltage is as a result applied to the windings. Consequently, this windings need to be designed such that such harmonics and DC voltages can be applied to them.
Correspondingly, the windings are subjected to corresponding AC voltage and DC
voltage testing before use. In the case of such DC voltage testing, a test DC
voltage is applied to the windings individually in succession or all at once.

SUMMARY
The object of some embodiments of the invention is to specify a winding arrangement which has high dielectric strength.

The object may be achieved by a winding arrangement having at least two windings, which are arranged next to one another in a row and each of which is surrounded by a barrier arrangement formed with an insulating material, and each having a tubular electric shield in the region of each of the two winding end sides of at least one of the windings, each shield coaxially surrounding the at least one winding leaving an intermediate gap and extending axially outwards beyond the respective winding end side such that its axial height, in relation to the respective winding end side, is equal to or greater than half the radial width of the intermediate gap.

Owing to the fact that the windings are each surrounded by a barrier arrangement formed with insulating material, there is a high degree of electrical insulation with respect to a core limb which may be present and also with respect to a tank which may be present, which may have tank wall screens which are magnetic on the inside, and in which the winding arrangement is arranged, i.e. with respect to electrical parts lying outside the winding. In addition, the tubular electric shields in the region of each winding end side mean that the electrical field is guided there such that the barrier arrangement is subjected to as little electrical load as possible there. If one assumes that the barrier arrangement has at least one wall made of insulating material which surrounds the winding and in the process, in particular on the winding end sides of one winding, engages around the radially outer winding edge which is formed by the winding outer surface and the winding end side, the shields mean that, in particular, the electrical field strength, which is formed between the shield and the corresponding winding - in particular the winding edge of said winding - and occurs, for example, when a DC
voltage is applied to the windings or when they are subjected to DC voltage testing, enters the barrier arrangement such that it is essentially perpendicular to the surface of the wall of said barrier arrangement or emerges from said barrier arrangement again. In this case, very low tangential electrical field strength components thus occur, i.e. ones which are directed along the surface of the wall of the barrier arrangement. In one embodiment without shields, an electrical field which is essentially directed in the axial direction forms when a DC
voltage is applied in this manner, in particular in the regions of the barrier arrangement in which the winding edges of the two adjacent windings are close to one another. This causes strong, tangential electrical field strengths, which are directed along the surface of the wall of the barrier arrangement and which can lead to an electrical fault, to occur precisely in that region of the barrier arrangement which is adjacent to the outer winding edge. When designing the shields as regards the height in relation to the respective winding end side, by which height each shield extends beyond the winding end side, it has been shown that it is sufficient for effective field guidance if this height is at least half the radial width of the intermediate gap. To this extent, the height also needs to increase correspondingly as the radial width of the intermediate gap becomes larger. In particular when using the winding arrangement according to some embodiments of the invention for an inductor, in which the two electrical windings are connected in parallel, the design according to some embodiments of the invention of the winding arrangement has proved to be particularly advantageous. Providing the barrier arrangement and the electrostatic shields also makes possible a particularly compact design of the winding arrangement with the tank, since the electrical fields forming in particular when a DC
voltage is applied (as described) are guided and are also made uniform towards the outside, as a result of which the likelihood of a flashover between one of the windings and electrically conductive parts at another potential which are arranged outside the windings is reduced. A winding arrangement which is particularly safe in electrical terms is provided if all of the windings have, in the region of their winding end sides, the type of shields which are provided for the at least one winding.

In one preferred embodiment, the two electric shields are formed jointly with a continuous, tubular, joint shield which extends axially over the entire winding. As a result, corresponding screening towards the outside is achieved along the entire winding. This has proved to be particularly advantageous when the winding arrangement according to some embodiments of the invention is arranged in a tank, in which magnet core stacks, which are aligned parallel to the core yokes and are arranged in the interior of the tank on the tank wall, are provided outside the winding in order to improve the magnetic field guidance. In the case of winding arrangements without electric shields, increases in field strength forming at the corners and edges generally provided in the case of the magnet core stacks may lead to flashovers between the winding and the magnet core stacks. The electrical field profile between the winding and the tank wall or the magnet core stacks is made uniform by the electric shields, as a result of which the risk of an electrical flashover between the winding and the tank wall is considerably reduced.

The winding arrangement preferably forms an inductor for high-voltage DC
transmission systems (HVDC transmission systems). The winding arrangement according to some embodiments of the invention is particularly suitable for such an inductor.

In accordance with another preferred refinement, each of the two windings forms a respective external transformer winding of a respective transformer winding combination, each transformer winding combination having the external transformer winding which coaxially surrounds an internal transformer winding. In the process, the two transformer windings are magnetically coupled and serve the purpose of transforming an electrical phase, for example a polyphase electrical power supply system.

The winding arrangement is preferably part of a transformer for HVDC
transmission systems. In such HVDC transmission systems, a high DC voltage may be applied to the transformer; owing to the design according to some embodiments of the invention, the winding arrangement is thus particularly well suited for such a transformer.

The barrier arrangement may be designed, for example, for engaging around the outer winding edge such that the wall is formed with a tube, which radially surrounds the winding, is made of insulating material and protrudes beyond the winding end side, and with in each case an insulating material disk which closes the insulating material tube at each end side in the manner of a lid. In one preferred refinement, in the region of the winding end sides, each barrier arrangement has in each case at least one rounded-off outer flange ring which engages around the outer winding edge.

In one preferred refinement, the shields each have a screen for field guidance purposes in the region of their ends. The screen for field guidance purposes makes it possible to prevent high concentrations of electrical field strength in the region of the ends of the shields.

The winding arrangement is preferably arranged in a conductive tank.
According to one aspect of the present invention, there is provided a winding arrangement having at least two windings, which are arranged next to one another in a row and each of which is surrounded by a barrier arrangement formed with insulating material, and each having a continuous tubular electric shield extending axially over the entire winding, each shield coaxially surrounding one of the windings leaving an intermediate gap and extending axially outwards beyond a respective winding end side such that its axial height, in relation to the respective winding end side, is equal to or greater than half the radial width of the intermediate gap.

BRIEF DESCRIPTION OF THE DRAWINGS

The winding arrangement according to some embodiments of the invention will be explained in more detail below with reference to the drawing, in which:

figure 1 shows a sectional illustration of an inductor having the winding arrangement according to an embodiment of the invention, figure 2 shows a transformer having the winding arrangement according to an embodiment of the invention, figure 3 shows a detail of a first modification of a winding arrangement having a screen for field guidance purposes, and figure 4 shows a detail of a second modification of a winding arrangement having a screen for field guidance purposes.

DETAILED DESCRIPTION

Figure 1 shows a winding arrangement having two windings 1 and 2, which are arranged next to one another in a row and each extend along an axis 85 and 86.
The electrical connections of the windings 1 and 2 are omitted in figure 1 for reasons of clarity. Each of the windings 1 and 2 is surrounded by a respective barrier arrangement 3 and 4 formed from insulating material. Each of the barrier arrangements 3 and 4 has an outer flange ring 9, 10 and 11, 12, respectively, on each of the winding end sides 5, 6, 7 and 8. An inner flange ring 13, 14 and 15, 16 is also provided on the winding end sides 5, 6 and 7, 8 respectively. The outer flange rings 9., 10 and 11, 12 each engage around the radially outer winding edge 19 and 20, respectively, and 21 and 22, respectively, which are formed by the winding outer surface 17 and 18, respectively, and the adjacent winding end side 5 and 6, respectively, and 7 and 8, respectively. The inner flange rings 13, 14 and 15, engage around a respective radially inner winding edge 19A, 20A and 21A, 22A.

For screening purposes, the tubular joint shields 23 and 24 are provided in the case of both windings 1 and 2 in the regions of their winding end sides 5, 6 and 7, 8, respectively. The joint shields 23 and 24 surround the windings 1 and 2, respectively, leaving an intermediate gap 23A and 24A and are linked to ground potential, i.e. connected to ground potential via a connection. Here, the joint shields 23 and 24 each extend over the entire axial length of the associated windings 1 and 2, respectively, and at the winding end sides 5, 6 and 7, 8, respectively, beyond the winding end sides, to be precise such that, as is explained by way of example using the joint shield 23, the axial height B in relation to the winding end side 5 is more than half the radial width A of the intermediate gap 23A.

If one considers, for example, the winding edge 19, said winding edge 19 is particularly well electrically insulated with respect to conductive parts, such as the core 25, the tank 26 or the magnet core stack 28 arranged in the tank 26 on the wall 27 of said tank, which are arranged outside the winding 1 by means of the outer flange ring 9. The joint shield 23 also makes it possible in this region to guide the electrical field originating from the winding end side 5 and the winding outer surface 17 in the region of the winding edge 19 and produced during operation or during DC
voltage testing such that it is virtually perpendicular to the surfaces 29 and 30 of the outer flange ring 9 and ends at the shield 23. To this extent, the electrical load on the barrier arrangement 3 in the region of the winding edge 19 when a DC voltage is applied during operation or during DC voltage testing is low.

If the joint shields 23 and 24 were not to be provided, an electrical field would be produced, in particular when a DC voltage is applied, in particular simultaneously, to the windings 1 and 2 in the region of the winding edges 19 and 21 which lie very close to one another, i.e. in the core window 31 of the core 25, and this electrical field would extend essentially in the axial direction, i.e. no longer perpendicularly to the surfaces 29 and 39 of the outer flange ring 9 and the corresponding surfaces of the outer flange ring 11.
This would result in a high electrical load along the surface 29 or 30, in particular in the region close to the winding edge 19, which may lead to an electrical fault.
The barrier arrangements 3 and 4 with their outer flange rings 9, 10, 11 and 12 and the inner flange rings 13, 14, 15 and 16 are formed in particular from pressboard.
The transformer tank 26 may be filled with an insulating medium, for example cooling oil.

Furthermore, it is also possible for the joint shield 24 to be omitted. Likewise, the core 25 may also be omitted so as to produce a core-less inductor.

Figure 2 shows a sectional illustration through a winding arrangement provided for a two-phase transformer.

Two transformer winding combinations 32 and 33 are provided which each extend along an axis 87 and 88, respectively, the transformer winding combination 32 having an external transformer winding 34 and an internal transformer winding 35, and the second transformer winding combination 33 having an external transformer winding 37 and an internal transformer winding 36. The respective external transformer windings 34 and 37 coaxially surround the respective internal transformer windings 35 and 36. Here too, the electrical connections of the transformer windings 34, 35, 36 and 37 are not illustrated for reasons of clarity. Each of the transformer windings 34, 35, 36, 37 is surrounded by a barrier arrangement 38, 39, 40, 41 associated with it. Each of the barrier arrangements 38, 39, 40, 41 has outer flange rings 42, 43, 44, 45, 46, 47, 48 and 49 which are comparable to the outer flange rings 9, 10, 11 and 12 shown in figure 1 and inner flange rings 50, 51, 52, 53, 54, 55, 56, 57 which are comparable to the inner flange rings 13, 14, 15 and 16 shown in figure 1.

Tubular electric shields 62, 63 and 64, 65 surrounding the transformer windings 34 and 37, respectively, are provided in the region of the winding end sides 58, 59, 60 and 61 of the external transformer windings 34 and 37. The electric shields 62, 63, 64 and 65 surround their respective winding so as to form a respective intermediate gap 62A, 63A, 64A and 65A. In comparison to the winding arrangement shown in figure 1, in this case, for example, the two individual shields 62 and 63 are provided in place of the joint shield 23 and each extend only over part of the axial length of the transformer winding 34. In other words: The joint shields 23 and 24 combine both the function of the two shields 62 and 63 and, respectively, 64 and 65. The shields 62, 63, 64 and 65 also extend in the axial direction beyond the respective winding end side 58, 59, 60 and 61 such that, as explained using the example of the shield 62, their respective axial height D in relation to the winding end side 58, 59, 60, 61 is at least equal to half the radial width C of the intermediate gap 62A.

The winding arrangement shown in figure 2 is arranged within a transformer tank 66. Each of the transformer winding combinations 32 and 33 surrounds a core limb 67 and 68, respectively, of a transformer core 69; the core limbs 67 and 68 are connected magnetically via core yokes 70 and 71 to form a closed magnetic circuit.
Magnet core stacks 74 and 75 are provided on the insides 72 and 73 of the transformer tank 66 in order to improve the magnetic field guidance.

In this arrangement too, the barrier arrangements 38 to 41 may be formed from pressboard, and the transformer tank 66 may likewise be filled with an insulating medium, for example cooling oil.

The electric shields 62, 63, 64 and 65 have the same function as the joint shields 23 and 24 shown in figure 1, namely, in particular in the core window 76 of the transformer core 69, of guiding the electrical field such that it passes tangentially through the outer flange rings 46 and 42 and, respectively, 43 and 47 and the barrier arrangement 38 and 40 is subjected to a low electrical load.

In place of the joint shields 23 and 24 shown in figure 1, the shields 62 to 64 shown in figure 2 may also be provided there.

On the other hand, the shields 62 and 63 and/or 64 and 65 shown in figure 2 may in each case be replaced by corresponding axially continuous joint shields, as shown in figure 1, in the winding arrangement shown in figure 2. The shields 62 and 63 are in this case formed jointly, i.e. integrally, with a continuous joint shield which extends axially over the entire winding; the same applies in this case to the shields 64 and 65. Furthermore, the transformer core 69 may be omitted in this case too. The shields 64 and 65 may also be omitted in this embodiment, and the shields 62 and 63 are sufficient for screening purposes;
however, in order to achieve particularly effective screening, shields 62, 63, 64 and 65 are provided in the region of all of the winding end sides 58 to 60.

The barrier arrangements 3, 4 shown in figure 1 and 38 to 41 shown in figure 2 may be formed with two or more layers, i.e. with two or more outer flange rings and inner flange rings.

The shields 62 to 65 and 84 and the joint shields 23 and 24 may have screens for field guidance purposes in the region of their ends, as illustrated in each case in figures 3 and 4.

Figure 3 shows a detail lying in the region of a winding end side 79 of a winding 77. The winding 77 extends along an axis 78 and is surrounded by a shield 81 leaving an intermediate gap 80, and said shield 81 is to be regarded as being representative of the shields 62 to 65 or the joint shields 23 and 24. In the region of its end 82, the shield 81 has a screen 83 for field guidance purposes. This screen 83 surrounds the axis 78 and extends in the circumferential direction of the shield 81 along the end 82. The screen has two conductive wires 84 and 84A which are each electrically insulated by a corresponding insulation 89 and 89A and jointly by a joint insulation 90. The two conductive wires 84 and 84A are connected to ground potential. The two wires 84 and 85 are interrupted at least once along their length along the circumference of the shield 81 such that there is no closed winding. The screen 83 serves the purpose of preventing excessive fields or high field concentrations in the region of the end 82 of the shield 81.

Figure 4 shows a modified screen 91 for field guidance purposes; it has an individual conductive wire 92 when compared with the screen 83 shown in figure 3, said wire 92 being surrounded by an electrical insulation 93. The wire 92 is also connected to ground potential and is interrupted at least once along its length along the circumference of the shield 81 such that there is no closed winding.
The screens 83 and 91 are intended to ensure that no excessive fields occur at the end 82 of the shield 81.
They may also be in the form of an electrical, conductive tube running around the axis 78 along the end of the shield 81, for example having a circular or elliptical cross section. A conductive foil may also be provided in place of a tube on a correspondingly formed mount. The screens 83 and 91 may also be formed with the shield 81 itself by the shield 81 being bent back so as to form a rounded-off brim, or it may also by bent back to such an extent that the bent-back part produces a type of circumferential tube.

The shields 62 to 65 and the joint shields 23 and 24 may each have a screen 83 or 91 for field guidance purposes in the region of its ends.

Claims

CLAIMS:

1. A winding arrangement having at least two windings, which are arranged next to one another in a row and each of which is surrounded by a barrier arrangement formed with insulating material, and each having a continuous tubular electric shield extending axially over the entire winding, each shield coaxially surrounding one of the windings leaving an intermediate gap and extending axially outwards beyond a respective winding end side such that its axial height, in relation to the respective winding end side, is equal to or greater than half the radial width of the intermediate gap.

2. The winding arrangement as claimed in claim 1 which forms an inductor for high-voltage DC transmission systems.

3. The winding arrangement as claimed in claim 1, wherein each of the two windings forms a respective external transformer winding of a respective transformer winding combination, each transformer winding combination having the external transformer winding which coaxially surrounds an internal transformer winding.

4. The winding arrangement as claimed in claim 3, which is part of a transformer for high-voltage DC transmission systems.

5. The winding arrangement as claimed in any one of claims 1 to 4, wherein in the region of the respective winding end side, the barrier arrangement has in each case at least one outer flange ring which engages around the radially outer winding edge.

6. The winding arrangement as claimed in any one of claims 1 to 5, wherein the shields each have a screen for field guidance purposes in the region of their ends.

7. The winding arrangement as claimed in any one of claims 1 to 6, which is arranged in a conductive tank.

8. The winding arrangement as claimed in any one of claims 1 to 7, wherein the windings each surround a core limb of a transformer core.