EP3984054B1 - Interrupter unit having a vacuum tube and an insulating housing - Google Patents

Description

The invention relates to an interrupter unit according to the preamble of patent claim 1.

To avoid climate-damaging sulfur hexafluoride, modern interrupter units are either filled with alternative insulating gases or combinations of vacuum interrupters with surrounding air insulation are used. In the second case described, a common structure is designed in such a way that a vacuum interrupter is in turn arranged in another closed space in which cleaned air or another air-like gas mixture is located. In order to further increase the insulating capability of such an arrangement, it is expedient to enclose the vacuum interrupter, the outer circumference of which is formed at least partially by an insulating material, for example an insulating ceramic, with a further insulating housing, in particular on a plastic basis such as epoxy resin . This insulating housing is thus arranged between the outer circumference of the vacuum interrupter and the gas space, which contains clean air, for example. The insulating housing is pushed over the vacuum tube or the insulating housing is cast around the vacuum tube in a casting process. In both alternative methods, it is always difficult to make an interface between the vacuum tube and the insulating housing free of air bubbles or other inclusions. Such bubbles in turn lead to partial discharges in this area during operation, as a result of which the material of the insulating housing is subject to erosion. The material is attacked at this point and loses its electrical insulating ability. In the worst case, long-term damage to the material of the insulating housing can lead to a breakdown in the boundary layer or a breakdown to the outside into the gas space. A breaker unit with a vacuum interrupter, arranged in an insulating housing, z. B. from the WO 00/41199 A1 known.

The object of the invention is to provide an interrupter unit with a vacuum interrupter and an insulating housing which, compared to the prior art, has improved protection against partial discharges in the border area between the vacuum interrupter and the insulating housing and thus prevents premature damage or erosion of the material of the insulating housing becomes.

The solution to the problem consists in an interrupter unit with the features of patent claim 1.

The interrupter unit according to claim 1 comprises a vacuum interrupter and an insulating housing, the insulating housing having an inner surface and the vacuum interrupter being at least partially bounded by an electrically insulating structural material. The structural material in turn has an outer surface, with the insulating housing at least partially surrounding the vacuum interrupter. In an operational state of the interrupter unit, the inner surface of the insulating housing and the outer surface of the vacuum interrupter are separated from one another by an adhesion layer. The invention is characterized in that both the inner surface and the outer surface are at least partially provided with a conductive layer, so that the following layer sequence results in a border area between the vacuum interrupter and the insulating housing, directed radially outwards from a switching axis: First comes from the inside to the outside the structural material of the vacuum interrupter. This structural material has the outer surface, which in turn is provided with a conductive layer or includes such a conductive layer. There then follows an adhesion layer, which is surrounded by a further conductive layer on the insulating housing or on its inner surface, and this further conductive layer is on the Inner surface of the insulating housing attached. A volume material of the insulating housing also follows.

The layer sequence described comprises two electrically conductive layers which delimit the adhesion layer from both sides when viewed radially. During operation of the interrupter unit, in particular during a switching process in which a corresponding electrical field is directed radially outwards from the switching axis, this means that the two conductive layers on the one hand on the structural material of the vacuum interrupter and on the other hand on the inner surface of the insulating housing are the same have potential. This in turn means that there is no electric field in the adhesion layer, which is located between the two conductive layers and in which there are also possible air pockets. The adhesion layer is therefore field-free. Due to the local absence of an electrical field in the area of the adhesion layer, there is no partial discharge in the area of any air inclusions or gas bubbles and therefore no local erosion of the affected material. In this way, the service life of the combination of interrupter unit and insulating housing and its operational reliability is significantly increased compared to the prior art.

It should be noted that the adhesion layer is preferably an adhesive layer that is additionally introduced between the two conductive layers. In principle, however, the two conductive layers can also be designed in such a way that they interact with one another through a corresponding process treatment, for example heat treatment, again for example through diffusion processes, so that the adhesion layer forms in the border region between the two electrically conductive layers. The adhesion layer could thus also emerge from the two conductive layers. The term electrically conductive also means a semiconductive material that is based on conventional semiconductor materials, for example such as silicon, silicon carbide or compound semiconductors such as gallium arsenide or includes this. The electrical conductivity of the layer is dimensioned in such a way that the electrical resistance of the layer in the axial direction is in a range between 10 ⁸ and 10 ¹⁵ ohms.

Furthermore, it is expedient for the insulating housing to have a decreasing permittivity radially outward, starting from the switching axis. The permittivity at the outer edge of the insulating housing is preferably as close as possible to 1, which means a small jump in field strength at the transition to the outer insulating medium, for example the cleaned air. Realistic values for the permittivity of well-suited materials for the insulating housing, such as e.g. B. plastics, especially based on epoxy resin are between 1.2 and 2, especially between 1.2 and 1.5. The permittivity in the insulating housing can decrease in steps radially outwards, which can be achieved by layering different materials in the insulating housing. A gradual change in permittivity radially outwards can also be useful and can be represented.

Further embodiments of the invention:
Further features and further exemplary embodiments are explained in more detail with reference to the following drawings. These are purely schematic representations that do not represent a restriction of the scope of protection.

Figur 1

eine Darstellung zur Herstellung einer Unterbrechereinheit mit einem Isoliergehäuse

Figur 2

eine vergrößerte Darstellung des Grenzbereichs zwischen Isoliergehäuse und Vakuumschaltröhre gemäß des Ausschnittes II aus Figur 1,

Figur 3

eine Abhängigkeit des elektrischen Feldes entlang der radialen Ausdehnung r gemäß III aus Figur 1.

show:

figure 1

an illustration of the production of an interrupter unit with an insulating housing

figure 2

an enlarged view of the border area between the insulating housing and the vacuum interrupter according to section II figure 1 ,

figure 3

a dependency of the electric field along the radial extent r according to III figure 1 .

In figure 1 the structure or the creation of an interrupter unit 2 with a vacuum interrupter 4 and an insulating housing 6 is illustrated. In the illustration on the far left according to a, a vacuum interrupter 4 is shown which has a structural material 22 which surrounds a vacuum space 28 . Two switching contacts 26 are shown schematically in the vacuum space 28 , at least one of which can be moved translationally along a switching axis 20 . The outer shape of the vacuum interrupter 4 is to be understood purely schematically, the structural material 22, which usually consists of an insulating ceramic material or includes this, usually only represents part of a housing of a vacuum interrupter 4. In particular in one area , In which the switching contacts 26 move along the switching axis 20, the vacuum interrupter 4 is delimited on the outside by a metallic outer material.

Furthermore, according to sub-figure b in figure 1 a conductive or semiconductive layer 16 is applied to an outer surface 10 of the vacuum tube 4 or the structural material 22 . This is, for example, a powdered silicon carbide material that is embedded in an epoxy matrix and has a SIC filling level of between 50 and 70 percent of the total volume. The resulting layer 16 has a conductivity which is dimensioned such that the electrical resistance of the layer is in a range between 10 ⁸ and 10 ¹⁵ ohms in the axial direction. The conductivity of the layer 16 is determined according to the resulting from the rated voltage and the specified geometric parameters of the vacuum interrupter and the resulting electric field.

Furthermore, according to part c, an insulating housing 6 is pushed over the vacuum interrupter 4 . In this case, the insulating housing 6 is configured cylindrically here schematically, where here a form-fitting application of the insulating housing 6 is illustrated. In principle, it is also possible or expedient to cast the insulating housing 6 onto the vacuum interrupter 4, in particular onto the structural material 22. However, a further conductive layer 14 which is attached to an inner surface 8 of the insulating housing 6 is expedient here. The same conditions that have already been explained for layer 16 apply to layer 16; in principle, layers 14 and 16 should be of the same type. However, they can also be different in terms of their material and their conductivity if, for example, different adhesion conditions and the resulting different coating processes make this necessary. This is expedient if the field freedom or field reduction between the layers 14, 16, to be described in more detail below, is achieved.

The interrupter unit is shown schematically in a finished state in partial figure d. The boundary area 18 between the structural material 22 of the vacuum interrupter 4 and a volume material 24 of the insulating housing 6 is in figure 1 represented by a circle, which is provided with the reference number II and its enlarged representation in FIG figure 2 is shown. figure 2 shows therefore this section, the boundary area 18 between the vacuum interrupter 4 and the insulating housing 6, wherein on the left side of the figure 2 the structural material 22 (for example aluminum oxide) is shown as the outer boundary of the vacuum interrupter 4 . This structural material 22 has an outer surface 10 on which a conductive layer 16 is applied. The composition of the conductive layer 16 has already been described in the previous paragraph. An adhesion layer 12 follows, which is preferably and essentially formed by an organic adhesive. Then follows another electrically conductive layer 14, which is very similar in composition to layer 16 or even consists of the same material. This is applied to an inner surface 8 of the insulating housing 6 . The volume material follows 24 of the insulating housing 6. This material is preferably an epoxy resin.

According to figure 2 12, bubbles 32 are shown between layers 16 and 14 in adhesion layer 12. FIG. These bubbles 32 form undesirably, but are difficult to avoid when the insulating housing is applied to the vacuum interrupter 4 or to the structural material 22 of the vacuum interrupter 4 . It should be noted here that the sequence of the layers in the boundary region 18 is described along the arrow r, which describes a radial sequence starting from the shifting axis 20 outwards.

In figure 3 , which also represents the electric field seen along the radial extension of the arrow r from the switching axis 20, it can be seen how the electric field weakens continuously starting from the switching axis 20 in the vacuum space 28. The offset of the field strength in figure 3 , which is separated in the area 28 by the two dashed lines, only shows that this is a section, which means that in a true-to-scale representation this area 28 in figure 3 would have a greater extent. A real jump in electric field strength occurs with the appearance of the structural material 22, in which case the field penetrates from the vacuum into the structural material 22, which has a higher permittivity than the vacuum in the vacuum space 28, and therefore the electric field strong is reduced. Here, too, the electric field E gradually decreases radially outwards.

The layers 12, 14 and 16 then follow along the arrow r in the radial direction figure 3 it can be seen that there is no electric field in this area. This is followed by the volume material 24 of the insulating housing 6, in which the electric field E continues to decrease until the air space 30 begins on the outer surface of the insulating housing 6, which also has an insulating effect. In this air space 30 can be cleaned air, but also normal air, i.e. an outside atmosphere, but also an air-like mixture that includes nitrogen and carbon dioxide. This is a further level of isolation for the breaker unit 2 in which the electric field continues to decrease.

In figure 3 a jump between the material 24 of the insulating housing 6 can again be seen with respect to the electric field. This is because the permittivity of the air or gas outside the insulating case 6 is close to 1. The material 24 of the insulating housing 6 usually has a higher permittivity, and it would be desirable for the permittivity of the material 24 to decrease along the radius, so that the jump that can be seen here between the transition from 24 to the area 30 reduced and as low as possible. For this purpose, it can be expedient for the volume material 24 of the insulating housing 6 to have different permittivities along the arrow r. Basically, the permittivity of the material outdoors should be as low as possible, i.e. as close to 1 as possible. Inside, the permittivity can be higher. This can be achieved by a layered structure of the volume material 24, so that two or more layers of different material with different permittivities are placed concentrically around one another. However, it is also expedient to design the material in such a way that there is a gradient-like behavior of the permittivity in the direction of the arrow r.

In areas 12, 14 and 16, where according to figure 3 the electric field is zero or near zero, the electrically conductive layers 14 and 16 sandwiching the adhesion layer 12 are positioned as described. As in figure 2 shown, bubbles 32 can occur in the adhesion layer 12, in which a partial discharge can occur when an electric field is applied, whereby the material of the adhesion layer or also the surrounding material or the volume material 24 of the insulating housing 6 erodes and ultimately ages. This aging process can reduce the dielectric strength and thus also the service life of the combination of insulating housing 6 and interrupter unit 2 and thus necessitate an earlier replacement. However, due to the layers 14 and 16 described, the adhesion layer 12 is embedded in such a way that the same potential is present on its inside and outside and the electric field there therefore drops to zero and therefore no partial discharge in the critical area of the adhesion layer 12 , in which bubbles 32 can form, takes place. The risk of erosion in this transition or boundary area 18 is reduced to almost zero by the layers 14 and 16 described.

It should be noted here that the adhesion layer 12 is generally an adhesive layer that is suitable for gluing the material 24 of the insulating housing 6 to the structural material 22 of the vacuum interrupter 4 . In principle, it can also be expedient to bring the layers 14 and 16 directly onto one another and to subject them to a corresponding treatment so that an adhesion layer forms between them, or the adhesion layer 12 is formed directly by the layers 14 and 16 . This can involve, for example, diffusion processes or chemical conversion in a further border area between these two layers 14 and 16 . This measure also helps to suppress bubbles 32 and, if they do occur, to render them harmless with regard to a partial discharge by embedding them in materials with the same potential.

Reference List

2

breaker unit

4

vacuum interrupter

6

insulating housing

8th

inner surface insulating housing

10

outer surface vacuum tube

12

adhesion layer

14

conductive layer inner surface

16

conductive layer outer surface

18

border area

20

shift axis

22

structural material

24

vacuum material insulation housing

26

switching contacts

28

vacuum space

30

air space/gas space

32

Blow

Claims (8)

1. Interrupter unit comprising a vacuum switch tube (4) and an insulating housing (6), wherein the insulating housing (6) has an inner surface (8) and the vacuum switch tube (4) is bordered at least partially by an electrically insulating structure material (22), which has an outer surface (10), and the insulating housing (6) at least partially surrounds the vacuum switch tube (4), wherein, in an operational state of the interrupter unit (2), the inner surface (8) of the insulating housing (6) and the outer surface (10) of the vacuum switch tube (4) are separated by an adhesion layer (12), characterized in that both the inner surface (8) of the insulating housing and the outer surface (10) of the vacuum switch tube are provided at least partially with an electrically conductive layer (14, 16) so that, in a boundary region (18) between the vacuum switch tube (4) and the insulating housing (6), the following layer sequence is produced in the radially outward direction from a switch axis (20): structure material (22) of the vacuum switch tube, outer surface (10) of the structure material (22), conductive layer (16) at the outer surface (10) of the structure material (22), adhesion layer (12), conductive layer (14) at the insulating housing (6), inner surface of the insulating housing (8), volume material (24) of the insulating housing (6).
2. Interrupter unit according to Claim 1, characterized in that the conductive layers (14, 16) comprise a semiconducting material.
3. Interrupter unit according to Claim 1 or 2, characterized in that the conductivity of the conductive layer is calculated such that the electric resistance of the layer in the axial direction is in a range between 10⁸ and 10¹⁵ ohm.
4. Interrupter unit according to one of the preceding claims, characterized in that the conductive layer contains silicon carbide.
5. Interrupter unit according to one of the preceding claims, characterized in that the insulating housing (6) has a decreasing permittivity in the radially outward direction starting from the switch axis (20).
6. Interrupter unit according to Claim 4, characterized in that the permittivity of the insulating housing decreases radially outwards in stages.
7. Interrupter unit according to one of the preceding claims, characterized in that the insulating housing has, at its radially outer edge, a permittivity which is between 1 and 2, in particular is between 1.2 and 1.5.
8. Interrupter unit according to one of the preceding claims, characterized in that the insulating housing is formed substantially by a plastic material, in particular by an epoxy resin.

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