KR20010049163A - A mechanically supported winding - Google Patents

Abstract

The invention relates to a power transformer (1) or reactor comprising a winding (3) consisting of a winding coil (2) with a concentric array winding turn, wherein at least one winding turn has a high voltage cable (111) with an outer semiconductor layer (115). Characterized in that the windings 3 are arranged axially between each winding turn, and the windings 3 have winding separation spacers 8, 9 arranged to be fixed in the axial direction. It relates to a power transformer (1) or a reactor.

Description

Mechanically Supported Windings {A MECHANICALLY SUPPORTED WINDING}

Current power transformers are generally oil cooled. The transformer is provided with a core comprising a core consisting of a plurality of core legs connected by yokes and a winding consisting of coils (first, second, regular) contained in a closed tank filled with oil. Heat generated in the coils and cores is removed by oil circulating internally through the coils and cores and is released into the ambient air through the conduit walls. The circulating oil is forcibly made by the oil pump or naturally by the oil internal temperature difference. The oil circulation is externally cooled with an air or water cooling device. External air cooling of the oil is forced and / or effected by natural convection. Oil has insulation in addition to the heat transfer role in high voltage oil cooled transformers.

Dry transformers are generally air cooled and normally cooled by natural convection when used at low power loads as current dry transformers. This technology is described in GB 1.147. Axial cooling ducts disclosed in 049 and made by corrugated windings, wherein the axial ducts for winding cooling inserted into mold resins are disclosed in EP 83107410 or the use of crossflow fans at full load is 7303919-0.

Moreover, conventional power transformers are provided with special rings to ensure the stability of the windings against short circuits. The winding is mounted as a unit to the core. The series of plates is mounted as a row that is tightly fixed to the barrier cylinder. All equipment is mounted in a row on the lower spacer ring. A compression ring for compressing the winding is located between the yoke of the core and the winding. Short circuits are prevented by iron yokes by clamps that place the laminate in place.

There is no iron core when the winding is used for reactive power compensation of the reactor. The winding in this case is formed only of coils.

U.S. Patent 5 036 165 discloses conductors in which the insulation is provided with an inner layer and an outer layer of semiconductor pyrolyzed glass fibers. For example, as described in US Pat. No. 5 066 881, it is known to provide a generator with a conductor having such an insulation, wherein the semiconductor pyrolytic glass fiber layer is in contact with two parallel bars formed of the conductor and The insulation is wrapped by the outer layer of semiconductor pyrolytic glass fibers. Pyrolytic glass fiber materials are preferred because they retain their resistance even after the implantation treatment.

The present invention relates to windings of air-cooled conductor power transformers and reactors and is provided with a spacer between the conductor windings to enable air cooling and grounding in a mechanically coupled winding structure.

1 shows an axial cross section of a winding core according to the invention.

2 shows plane A-A according to FIG. 1 of a winding coil with a spacer according to the invention.

3a shows a part of an upper end plate according to the invention.

3b shows a part of a lower end plate according to the invention.

4 shows a high voltage cable according to the invention.

It is an object of the present invention to make a winding of a new type of power transformer or reactor, the winding comprising a high voltage cable with an outer semiconductor layer. The windings are provided with spacers, which not only comprise means for applying axial compressive stress to the windings, but are arranged to make cooling ducts between the concentric winding turns. The problem of the short circuit of the winding can be solved, for example, by making the clamp smaller and lighter, which pre-absorbs the force of the transformer. This reduces the eddy current of the clamp to reduce the overall eddy current loss.

The winding is mechanically in the form of a small integrated winding unit which absorbs stress, such as short circuit energy, without transmitting force to the iron core of the transformer.

It is a further object of the present invention to provide an axially cylindrical duct between each winding turn so that the coolant is correctly dispensed to meet the cooling requirements of the windings. Cylindrical ducts are made by spacers inserted during coil winding. Cooling flow is produced by the fan and spacers are sized to allow flow to occur in the ducts for each winding cooling regulation.

Another advantage of this transformer design is that it is mounted on a cable drum in a cable factory before the winding is mounted around the iron core in the field, which is a significant advance in this type of transformer manufacturing technology.

The present invention relates to the windings of a power transformer or reactor. The winding includes a high voltage cable wound around the transformer core. The windings extend axially along the length of the winding and in particular comprise a plurality of spacers that radially separate each winding cable turn to create an axial cylindrical cooling duct.

According to an embodiment of the invention the windings are arranged with an axial cylindrical cooling duct between each winding turn disposed outside and the ducts are made by spacers while winding the core.

According to an embodiment, the spacers are also arranged to axially clamp the windings together, in particular to form an integrated winding unit which absorbs mechanical short circuit energy.

Furthermore, the spacer is arranged with an elastic layer to absorb the vibration generated in the windings.

In the power transformer according to the invention, the winding is of a type corresponding to a cable with a solid, extruded insulator (for example a cable with an XLPE cable or an EPR insulator) as used for power distribution. The cable is composed of an inner electrical conductor composed of at least one stranded portion, an inner semiconductor layer surrounding the electrical conductor, a solid insulating layer surrounding the inner semiconductor layer, and an outer semiconductor layer surrounding the insulating layer. Such a cable is flexible, which is a very important property. Because the technique for the device according to the invention is basically based on a winding system in which windings are formed from cables which are bent during assembly. Flexibility of XLPE cables generally has a radius of curvature of about 20 cm for a 30 mm diameter cable and a radius of curvature of about 65 cm for an 80 mm diameter cable. In the present application, the term "flexible" means that the winding is bent downward with a radius of curvature of about 4 times the cable diameter, preferably 8 to 12 times the cable diameter.

The windings of the present invention should be configured to maintain their properties even when the windings are bent and thermally stressed during operation. In this connection it is particularly important that the layers maintain their adhesion to each other. The physical properties of the layers are important, in particular the elasticity and relative coefficient of thermal expansion. For example, in an XLPE cable, the insulation layer is made of crosslinked low density polyethylene, and the semiconductor layer is made of polyethylene mixed with soot and metal particles. Volume changes due to temperature changes are absorbed as cable radius changes, and due to the relatively small difference between the coefficients of thermal expansion of the layers with respect to the elasticity of these materials, radial expansion can occur without losing adhesion between the layers.

The foregoing material combinations should only be considered as examples. Other bonds and semiconductor states that meet certain conditions (ie, resistive ranges of 10 ⁻¹ to 10 ⁶ ohm-cm, for example 1-500 ohm-cm or 10-200 ohm-cm) are described herein. Falls within the scope of.

The insulating layer is for example a crosslinked material such as low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polybutylene (PB), polymethylpentene (PMP), crosslinked polyethylene (XLPE) or It consists of a rubber such as ethylene propylene rubber (EPR) or silicone rubber.

The inner and outer semiconductor layers have the same base material but are mixed with particles of conductor material such as chute or metal powder.

The mechanical properties of these materials, in particular the coefficient of thermal expansion, are relatively less affected by the mixing of the chute or the metal particles, at least in proportions required to achieve the conductivity required by the present invention. Therefore, the insulating layer and the semiconductor layer have the same coefficient of thermal expansion.

Ethylene-vinyl-acetate copolymers / nitrile rubbers, butyl graft polyethylene, ethylene-butyl-acrylate-copolymers and ethylene-ethyl-acrylates also constitute suitable polymers for semiconductors. Although different types of materials are used as the base of the various layers, it is preferable that their coefficient of thermal expansion is substantially the same. This is even more the case when the aforementioned materials are combined.

The aforementioned materials have a relatively good elasticity of E-modulus, where E < 500 MPa, preferably E < 200 MPa. The elasticity is such that a slight difference between the coefficients of thermal expansion for the material in the layer is sufficient to be absorbed in the radial direction of elasticity, so that no cracking or other damage occurs and the layers do not separate from each other. . The material of the layer is elastic and the adhesion between the layers has at least the same size as the weakest part of the material.

The conductivity of the two semiconductor layers should be large enough so that the potential along each layer is about the same. The conductivity of the outer semiconductor layer should be large enough to cover the electric field in the cable, but small enough not to cause losses due to the current induced in the longitudinal direction of the layer.

Thus, each two semiconductor layers consist of one equipotential surface and a winding, the electric field being surrounded by these layers. Of course, one or more additional semiconductor layers may be disposed on the insulating layer.

The invention is explained below with reference to the accompanying drawings.

1 shows a cross-sectional view of a power transformer 1 provided with a winding coil 2 having a winding 3 wound up in a spiral arrangement starting from the lower end plate 4. The windings do not have to be coupled together. Portions of embodiments of other windings with different cable diameters are shown in the figures. As shown in the figure, with different cable diameters of different cable turns, each winding is provided with axial spacers a, b, c for securing each winding of the coil in an axial position. Multiple spacers 8, 9 are inserted between each winding turn 5, 6, 7. In the figure the first spacer 8 is inserted between the first winding turn 5 and the second winding turn 6 arranged concentrically. The second spacer 9 is inserted between the second winding turn 6 and a similar concentric third winding turn 7. Insert the remaining spacers in this way. Each spacer 8, 9 of the winding coil 2 is clamped to the lower end plate 4 and tightly tightened by the clamping means 10 with respect to the upper end plate 11. As shown in FIG. 1, the first spacer 8 is thicker than the second spacer, for example making a wide duct between the winding turns. The winding coil includes its own part along the iron core, which need not be supported by the iron core to compensate for any short circuit energy that occurs. The winding structure does not necessarily contact the iron core in the so-called windows. Winding coil 2 wraps leg 12 of an iron core connected to yoke 13 to contact another leg (not shown) at the upper and lower ends. The spacers 8, 9 are cylindrical or rectangular in cross section and are provided with at least one end with clamping means in the form of nuts with screws or wedges. As shown in FIG. 2, the spacers 8, 9 are radially located outwardly in the form of "spokes" from the legs 12 of the iron core with the end plates 4, 11. The number of end plates varies between 8 and 16 depending on the size of the windings, but in the preferred embodiment there are 12 end plates 11 arranged around the entire winding coil. Five spacers are located radially through each "spoke" of this type of winding coil. Spacers 8, 9 additionally create axial cylindrical cooling ducts 13, 14 between the respective radially located windings 5, 6, 7. The winding turn is air cooled by pressurizing air through the duct by a fan (not shown). The spacers 8, 9 are located throughout the winding coil 2 and in the longitudinal axial direction. The spacer is inserted between the winding turns while winding the coil.

Therefore, each winding coil is surrounded by cooling ducts arranged for flowing cooling air. The cooling regime, which means that there is a different cooling flow in the concentric duct, depends on the windings. As described above, the spacers are arranged radially in different dimensions to achieve accurate cooling of the duct.

The first spacer 8 is a metal or reinforced plastic coated with a rubber layer 16 which functions as a spring to reduce the vibration of the windings during operation. The clamping means is designed as a wedge in the first embodiment and as a screw-bolt mechanism in the second embodiment. The winding unit is clamped so that the winding functions mechanically as a separate unit. The pressure applied during the clamp is sufficient to maintain the windings and is not higher than the gable's XLPE-insulator can withstand. In this embodiment, the transformer unit is mounted to the iron core in a suitable manner.

3a shows an upper end plate 11 which provides a numerical aperture of opening 16 which corresponds to the number of spacers 8. The spacer 8 extends through the opening 16 and is arranged to be axially tightened to the end plate 11 with a tensile resistance nut 18. When the spacer is electrically conductive, the end of the spacer is connected to the grounding means 20. Additionally, FIG. 3A shows a spacer 8 core 22 connected at the upper end to a welded upper bolt 31 provided with a screw 32 for tightening the nut 18 to the upper end plate 11. .

The core of the spacer 8 is connected to the lower bolt 34 welded at the lower end 33 as in the above method of providing the lower nut 36 and the screw 35 for tightening to the lower end plate 4 (FIG. 3 b). In the figure the winding turns are designed by reference numerals 1-8 such that the innermost winding turn is designated by reference 1 and the outermost turn by reference 8. As shown in the figure, each spacer 8 is provided with flexible braking means 40, preferably made of rubber. The thickness of the braking means 40 is adjusted according to the distance between the winding turns, depending on the fact that the difference of the winding turns is formed of a cable having a different diameter. Moreover, the winding unit is locked to the core of the transformer by a core detenter 42 which is screwed to the lower bolt 34 which is screwed into the transformer core via the reference plate 44. .

4 is a cross-sectional view of the high voltage cable 111 used for the windings according to the invention. The high voltage cable 111 comprises a number of stranded wires 112 having a circular cross section of, for example, copper (Cu). The twisted pair 112 is arranged at the center of the high voltage cable 111. The first semiconductor layer 113 is arranged around the strand 112. An insulating layer 114, for example XLPE insulator, is arranged around the first semiconductor layer 113. The second semiconductor layer 115 is arranged around the insulating layer 114. Therefore, the concept of a high voltage cable of the present invention generally does not include an external protective screen that encloses something like a power distribution cable. High voltage cables have a diameter of 20-250 mm and a conduction area of 40-3000 mm ² .

Claims (14)

A power transformer (1) or reactor comprising a winding (3) consisting of a winding coil (2) having a concentric array winding turn, At least one winding turn is formed by a high voltage cable 111 having an outer semiconductor layer 115, in which the windings 3 are arranged axially between each winding turn, and the windings 3 are fixed axially. Power transformer or reactor, characterized in that it has a winding separation spacer (8, 9) arranged to be. The support means according to claim 1, wherein the spacers (8, 9) extend radially on both sides of the winding coil (2) to form a mechanical winding structure with windings concentrically arranged in a cage-like structure. And (4,11) arranged in cooperation with. 3. The support means (4) and (11) are formed as an upper end plate (11), and the upper end plate (11) is provided with an opening (16) from which spacers (8, 9) extend. And (8,9) is arranged to be axially tightened with respect to the end plate (11). 4. Device according to claim 3, characterized in that the upper end plate (11) extends from the innermost winding turn (5) to the outermost winding turn for the entire winding coil. 5. Device according to claim 4, characterized in that the plurality of support means (4,11) are arranged radially on at least one entire face of the winding coil (2) to form a spoke shaped support surface. 6. The support according to any one of claims 2 to 5, wherein the support means (4, 11) are formed of a lower end plate (4) on which the spacers (8, 9) are clamped, or on the lower end plate (4). And 11) an opening (16) extending from the spacer arranged such that the spacer (8,9) is axially fixed. 7. Device according to claim 6, characterized in that the plurality of lower end plates (4) are arranged radially on the entire side of the winding coil (2) which forms the spokes of the lower support surface. 8. The device of claim 7, wherein the outer semiconductor layer (115) is grounded. 9. The winding of claim 1 wherein the winding is flexible and includes a conductive core surrounded by an inner semiconductor layer 113, an insulating layer 114 of a solid surrounding the inner semiconductor layer 113, and the insulation. An outer semiconductor layer (115) surrounding the layer (114), said layers (113, 114, 115) being attached to each other. 10. The material according to any one of claims 1 to 9, wherein the layers 113, 114 and 115 are made of a material having an elastic modulus and a coefficient of thermal expansion such that volume changes of the layers 113, 114 and 115 resulting from temperature changes during operation are absorbed by the elasticity of the material. And thus the layers (113, 114, 115) are adapted to adhere to one another even with temperature changes occurring during operation. Device according to one of the preceding claims, characterized in that the material of the layer (113, 114, 115) preferably has a high modulus with an elastic modulus of 500 MPa or less, preferably an elastic modulus of 200 MPa or less. 12. The device according to any one of the preceding claims, wherein the coefficient of thermal expansion of the layer (113, 114, 115) material is the same. 13. Apparatus according to any of the preceding claims, wherein the adhesion between the layers (113, 114, 115) is at least equal to the adhesion of the weakest part. 14. An apparatus according to any one of the preceding claims, wherein each semiconductor layer (113, 115) constitutes one equipotential surface.