EP2661759A1 - Transformer winding - Google Patents

Abstract

The invention relates to a transformer winding (10, 50, 70) comprising at least two hollow-cylindrical, axially adjacent winding modules (12, 14, 52, 54, 72, 74, 76, 78), which are arranged about a common winding axis (16, 56, 80) and have an electrical conductor (18, 20) wound in layers, and a common electrical insulting layer (22, 68, 82), by means of which the winding modules (12, 14, 52, 54, 72, 74, 76, 78) are enveloped. The insulating layer (22, 68, 82) has at least one annular, radial depression (28, 30, 58, 60, 62, 64, 66, 84, 86, 88) or annular, radial elevation (32), which is salient transversely to the winding axis (16, 56, 80) on the radial outer face (24, 90) of said insulating layer (22, 68, 82).

Description

 transformer winding

description

The invention relates to a transformer winding comprising at least two hollow cylindrical axially adjacent winding modules arranged around a common winding axis with a layer-wound electrical conductor and a common electrical insulation layer, by which the winding modules are enveloped.

It is well known that power transformers, for example, with a rated power of a few MVA and in a voltage range of, for example, 5kV to 30kV or 110kV, sometimes even up to 170kV, are also designed as dry-type transformers, wherein in the latter voltage range well rated power of 50MVA and are possible about it. The hochspannungssei- term windings are usually isolated by a mixture of glass roving and epoxy resin, the insulation layer formed therefrom usually encloses the winding.

For structural reasons, it is also customary to construct such a winding of a plurality of winding modules, that is, from a plurality of axially adjacent hollow cylindrical winding segments, which are preferably electrically connected to each other radially inside and thus electrically connected in series. As a result, the voltage stress between radially adjacent winding layers is reduced and thus also the corresponding required insulation effort. However, this has the consequence that when operating the winding between axially adjacent winding modules at their end faces an increased Spannungsdif-

CONFIRMATION COPY occurs, which leads to an increased stress on the interposed insulating layer. Of course, a corresponding voltage stress also occurs when galvanically isolated windings are arranged axially adjacent. The insulating material as such is readily dimensioned such that it can withstand this stress in its interior.

Under a hollow cylindrical winding is according to the invention not only a winding with a circular cross-section to understand, but this term also includes an approximately rectangular cross-section with rounded corners. In this way, the winding window available is optimally utilized when the winding is installed on a transformer core having a rectangular cross section.

The disadvantage, however, is that along the outer surface of the insulating layer of the winding and in particular over the region of the axially adjacent winding segments also builds up a potential difference. This can lead along the outer surface of the common insulation layer of the winding to unwanted discharges or partial breakdowns, which is still favored by a possible contamination of the outer surface.

Based on this prior art, it is an object of the invention to provide a transformer winding, which has an improved insulation behavior along the outer surface of the insulating layer.

This object is achieved by a transformer winding of the aforementioned type. This is characterized in that the insulating layer has at least one transverse to the winding axis pronounced annular radial recess or elevation on its radial outer surface.

Such an annular radial depression or elevation advantageously extends the creepage path along the axial extent of the surface, wherein the voltage stress also takes place along the axial surface due to the axially adjacent arrangement of the winding modules. Thus, similar to ribs of a ceramic insulator, an increase in the voltage carrying capacity is achieved. is sufficient, with an increase in size - at least in the case of wells - avoided in an advantageous manner. The configuration of a depression or an elevation may, for example, have a rectangular, semicircular, parabolic, umbrella-like or else Gaussian curve-like cross section. What is essential is ultimately an extension of the creepage path along the surface and the avoidance of the formation of a continuous moisture film on the surface.

According to a particularly preferred embodiment of the transformer winding according to the invention encloses the at least one annular radial recess or survey the transformer winding completely, ie at an angle of 360 ° about the winding axis. Thus, advantageously, an extension of the axial creepage path takes place uniformly over the entire circumference of the winding. In addition, this makes the production of the insulating layer, which is usually also wound, simplified accordingly. But also, for example, a subsequent milling a ring-like radial recess in an existing insulating layer is simplified.

According to a likewise preferred variant, at least one annular radial depression is arranged between the at least two axially adjacent winding modules. There is to be calculated as mentioned above with the highest voltage difference or field strength, which is why an extension of the creepage path particularly advantageous effect on the insulation capacity of the winding. In addition, such a depression can be made deeper there than directly above a winding module, because the depression can protrude into the intermediate space between the axially adjacent winding modules. In this way, the creepage distance is extended in the isolationistically critical area in a particularly effective manner.

A recess arranged in this way can be realized particularly effectively according to the invention if a radially outer winding layer of a winding module is shortened axially with respect to winding layers located radially below it. Then, the space available between the axially adjacent winding modules is increased in the radially outer area, where half there is also provided an enlarged space for the arrangement of a radial annular recess. The insulation resistance is thus advantageously increased with a corresponding design of the depression.

According to the invention, the transformer winding can be produced particularly simply if it is arranged on a coil former. As also manufacturing technology advantageous, it turns out when the winding is limited at its two axial end faces of one end plate. Then, in fact, a kind of laterally limited bobbin is formed, which is particularly suitable for a winding process, wherein preferably both the electrical conductor and the insulating layer are wound in a common manufacturing process.

According to a variant embodiment of the winding according to the invention, this has at least two winding modules, which are electrically connected to each other radially inside. By dividing a high-voltage winding into a plurality of winding modules, the voltage stress between adjacent winding layers is advantageously reduced, which advantageously reduces the insulation effort between the layers. When using four series-connected winding modules then preferably the two axially outer with the two axially inner winding modules are electrically connected radially inside and the two inner winding modules radially outward. However, it is also provided according to the invention that the winding comprises at least two groups of two radially inwardly electrically connected winding modules, which are not necessarily galvanically connected to one another.

According to a particularly preferred embodiment of the winding according to the invention, the common electrical insulation layer has a wound insulating material, for example a fiber roving. This can be wound production technology together with the electrical conductor, wherein the fiber roving is soaked, for example, with a moist epoxy resin. After such a winding process, the winding is then to cure the resin to a polymerization temperature, depending on the used resin, for example, 160 ° C, to heat, so that the resin then cures completely. However, the use of a dry or at least tacky, tape-like insulating material proves to be particularly advantageous for winding recesses or elevations according to the invention, because this is significantly more dimensionally stable during the winding process. Thus, for example, the winding of a survey with rectangular cross-section is particularly easy by a corresponding number of winding layers of a dry insulation tape are wrapped one above the other.

However, the insulating ability of a dry wound insulation tape or fiber roving is usually reduced due to the infinitesimal small gaps formed between the layers, especially since a correspondingly high mechanical stability is difficult to ensure, possibly by the use of an adhesive layer on a flat side of the insulating tape. Therefore, according to the invention, it is also provided that the wound insulating material is a fiber roving or glass fiber roving pre-impregnated with resin in the B state, which has been heated to a polymerization temperature after the winding process.

B-state of a resin means that the curing process of the resin has already started but has been discontinued intentionally so that the resin is in a state of incomplete polymerization. However, the B-state of a resin can also mean that this has been converted into a solid state by appropriate heating to a melting temperature of, for example, 80 ° C. and subsequent cooling, without the actual chemical reaction of the polymerization having already been initiated. In such a state, the resin can be remelted at a corresponding temperature, wherein the actual polymerization takes place at a temperature above the melting temperature, for example at a baking temperature in the range of 120 ° C to 140 ° C.

The use of such a resin, in particular epoxy resin, both a dimensionally stable winding process is possible as well as the subsequent reflow and polymerization process a particularly high insulation and mechanical stability.

According to a further embodiment of the transformer winding according to the invention, the common electrical insulation layer has a part by means the insulation material wrapped transversely to the winding axis arranged flexible profile strip, through which at least a portion of the radial annular depressions or elevations is formed. The profiled strip is made of an insulating material and protrudes preferably with a first part of the radial outer surface of the insulating layer and is arranged with a second in the insulating layer and thereby fixed that preferably parallel to the winding axis extending profile areas are fixed with wound insulation material. Ultimately, however, the profile strip is to be regarded as part of the insulating layer itself, by which the creepage path is extended in an advantageous manner.

According to a further variant of the transformer winding, the flexible profile strip has a T-shaped profile cross-section. This is particularly suitable to be anchored in the insulation layer. But there are also other profile shapes such as a multiple T cross-section, for example, a TTT cross-section, conceivable, which would then, if necessary, also be placed so deep in the insulation that it does not protrude but is formed by a depression.

According to another variant of the invention, the flexible profile strip consists at least predominantly of a silicone rubber. Because of the high material flexibility, this can be particularly easily adapted to the outer contour shape of a winding according to the invention, but of course also pre-bent and possibly less flexible profile strip pieces can be used.

The advantages of an improved insulation capability of a winding according to the invention also become apparent for a transformer which has a transformer core and, preferably, three windings according to the invention. These are needed to realize a three-phase transformer, as is common in power distribution networks.

Further advantageous embodiment possibilities can be found in the further dependent claims. Reference to the embodiments illustrated in the drawings, the invention, further embodiments and other advantages will be described in detail.

Show it:

1 shows a section through part of a first exemplary transformer winding,

 Fig. 2 is a section through the second exemplary transformer winding and

3 shows a section through part of a third exemplary transformer winding.

1 shows a section through part of a first exemplary transformer winding 10, which is arranged rotationally symmetrically about a winding axis 16. The winding is arranged on a bobbin 36, which is bounded at its axial ends by two end plates 38, 40. Two axially adjacent hollow-cylindrical winding modules 12, 14 are provided which each comprise a plurality of winding layers of a single conductor 18, 20. A winding layer is illustrated drawing technology as a horizontal line, which, however, symbolizes a plurality of axially adjacent turns of a conductor 18, 20, which in turn is arranged around the winding axis 16. The two winding modules 12, 14 are electrically connected in series with one another by means of a galvanic connection 34. By dividing the winding into two winding modules 12, 14, the voltage stress between the individual winding layers is advantageously halved. Both winding modules 12, 14 are surrounded by a common insulation layer 22, in this case a wound insulating material preimpregnated with an epoxy resin in the B state, which was finally heated to a polymerization temperature. The insulating layer 22 not only surrounds the outer surfaces of the winding, but it is also provided between them also between the individual winding layers and thus ensures the electrical insulation between the wound conductor layers.

During operation of the winding 10, the highest voltage stress on the radially outer surface 24 of the insulating layer results exactly between the two winding modules 12, 14. In order to avoid a discharge or a partial breakdown along the Au To avoid ßenfläche two annular radial 26 recesses 28, 30 and an intermediate elevation 32 are provided which serve in particular the extension of the creepage along the axial extent of the outer surface 24.

Provided radially inward is another winding 42, which is intended to symbolize a winding on the underside, whereas the radially outer winding according to the invention is intended to symbolize a winding on the high side with a rated voltage of, for example, 60 kV. In the case of a winding on the underwinding, an elongation of the creepage path according to the invention is not essential because of the lower stress load associated with a lower rated voltage of, for example, 6 kV.

FIG. 2 shows a complete section through a second exemplary transformer winding 50, that is to say with a partial section above the winding axis 50 and with a partial section below the winding axis 56. Arranged around the winding axis 56 are two hollow cylindrical and axially adjacent winding modules 52, 54, each with five winding layers are indicated. In the upper section, the galvanic connections of the layers to each other and the galvanic connection between the winding modules 52, 54 are shown, while only the winding layers are shown in the lower section. The two winding modules are surrounded by a common insulation layer 68. Arranged on the radial outer surface of the insulation layer 68 are five ring-shaped radial depressions 58, 60, 62, 64, 66, which serve to extend the creeping path. Depending on the structural boundary conditions, depressions prove to be more advantageous over surveys, because they have no additional space requirement and also allow material savings. The respective radially outer two winding layers are axially reset in the axial center of the winding 50, so that the annular radial recess 58 could be correspondingly deeper and larger than the other wells 60, 62, 64, 66. This proves to be particularly advantageous because in the axial gap between the two winding modules along the outer surface of the insulating layer is operatively expected to be the highest voltage stress. Therefore, the extension of the creepage path advantageously correlates with the local stress loading. 3 shows a section through a portion of a third exemplary transformer winding 70 disposed about a winding axis 80. The winding corresponds essentially to the winding 10 shown in FIG. 1, wherein, in contrast to this, however, four axially adjacent winding modules 72, 74, 76, 78 are provided which in each case comprise two galvanically interconnected sub-groups of the winding modules 72 and 74 and 76 and 78 are divided, the groups are in turn galvanically separated from each other. The winding modules 72, 74, 76, 78 are surrounded by a common insulation layer 82 or enclosed therein. The highest stress loads along the radially outer surface 90 occur in the axial direction between adjacent winding modules 72, 74, 76, 78. These are also exactly the areas where the creepage distance has been lengthened in the axial direction by corresponding radial ring-like depressions 84, 86, 88, so that a correspondingly increased dielectric strength results.

Another Kriechwegverlängerung in the region of the adjoining sub-groups 72, 74 and 76, 78 is realized by protruding from the insulating material flexible profile strips 90, 92, 94, wherein the arranged in the recess 86 profile strip protrudes only from the bottom of the recess, but not from the winding surface. The profile strips are made of an electrically insulating material such as a silicone rubber. In their lower, so radially inner region, the T-shaped profile strips are fixed by a plurality of the transverse T-bar enclosing layers of a wound insulation material. By creeping out of the radial surface of the insulating layer part then the Kriechwegverlängerung.

Reference numeral list Section through part of a first exemplary transformer winding first winding module of the first transformer winding

second winding module of the first transformer winding

winding axis

Head of first winding module

Head of second winding module

first common electrical insulation layer

Radial outer surface of the first insulating layer

radial alignment

first transverse to the winding axis recess

second transverse to the winding axis recess

first transversely to the winding axis extending survey

galvanic connection

bobbins

first face plate

second face plate

further transformer winding

Section through second exemplary transformer winding

first winding module of the second transformer winding

second winding module of the second transformer winding

winding axis

first transverse to the winding axis recess

second transverse to the winding axis recess

third transverse to the winding axis depression

fourth transverse to the winding axis recess

fifth recess extending transversely to the winding axis

second common electrical insulation layer

Section through part of a third exemplary transformer winding first winding module of the third transformer winding

second winding module of third transformer winding

third winding module of third transformer winding

fourth winding module of third transformer winding 80 winding axis

 82 third common electrical insulation layer

84 first extending transversely to the winding axis recess

86 second transverse to the winding axis recess

88 third transverse to the winding axis depression

90 radial outer surface of third insulation layer

92 first flexible profile strip

 94 second flexible profile strip

 96 third flexible profile strip

Claims

claims 1. transformer winding (10, 50, 70) comprising  at least two axially adjacent winding modules (12, 14, 52, 54, 72, 74, 76, 78) arranged in a hollow cylinder around a common winding axis (16, 56, 80) with a layer-wound electrical conductor (18, 20),  a common electrical insulation layer (22, 68, 82) through which the winding modules (12, 14, 52, 54, 72, 74, 76, 78) are enveloped, wherein the insulating layer (22, 68, 82) has on its radially outer surface (24, 90) at least one annular radial depression (28, 30, 58, 60, 62, 64, 66), which is pronounced transversely to the winding axis (16, 56, 80). 84, 86, 88) or annular radial projection (32), characterized in that the common electrical insulation layer (22, 68, .82) has a wound insulation material and a flexible profile strip (90, 92, 94) arranged transversely to the winding axis (16, 56, 80) partly by means of the insulation material, through which at least one Part of the radial annular recesses (28, 30, 58, 60, 62, 64, 66, 84, 86, 88) or protrusions (32) is formed. 2. Transformer winding according to claim 1, characterized in that the at least one annular radial recess (28, 30, 58, 60, 62, 64, 66, 84, 86, 88) or elevation (32) completely surrounds the transformer winding. 3. Transformer winding according to one of claims 1 or 2, characterized in that at least one annular radial recess (28, 30, 58, 60, 62, 64, 66, 84, 86, 88) between the at least two axially adjacent winding modules (12 , 14, 52, 54, 72, 74, 76, 78). 4. Transformer winding according to claim 3, characterized in that a radially outer winding layer of a winding module is axially shortened with respect to radially below it winding layers and the shape of the annular radial recess is adapted thereto. 5. Transformer winding according to one of the preceding claims, characterized in that it is arranged on a bobbin (36). 6. transformer winding according to one of the preceding claims, characterized in that it is limited at its two axial end faces of a respective end plate (38, 40). 7. Transformer winding according to one of the preceding claims, characterized in that at least two winding modules (12, 14, 52, 54, 72, 74, 76, 78) radially inwardly are electrically connected to each other (34). 8. Transformer winding according to claim 7, characterized in that these at least two groups (72 + 74, 76 + 78) of two radially inwardly galvanically interconnected winding modules (12, 14, 52, 54, 72, 74, 76, 78) includes. 9. transformer winding according to one of the preceding claims, characterized in that the wound insulation material is a dry insulation material. 10. Transformer winding according to claim 9, characterized in that the wound insulation material is a pre-impregnated with resin in the B state fiber roving, which was heated to a polymerization temperature after the winding process. 11. Transformer winding according to one of the preceding claims, characterized in that the flexible profile strip (90, 92, 94) has a T-profile. 12. Transformer winding according to one of the preceding claims, characterized in that the flexible profile strip (90, 92, 94) at least predominantly consists of a silicone rubber. 13. Transformer with a transformer core and at least one voltage-side and a high-voltage side transformer winding, characterized in that the high-voltage side transformer winding is designed according to one of claims 1 to 12.