EP3559968B1 - Insulation arrangement for a high or medium voltage assembly - Google Patents

Description

The invention relates to an insulator arrangement for a high-voltage or medium-voltage system according to the preamble of patent claim 1.

A ceramic material is often used as the insulating material in high and medium-voltage systems, in particular switchgear. The insulating capacity of these solid bodies is generally quite high. Defects in the lattice structure or grain structure of the ceramic materials can lead to a breakdown at high voltages, in particular higher than 72kV. i.e. With these materials, the breakdown field strength E _bd is reached above a critical electrical voltage or a critical potential. However, the critical breakdown field strength _Ebd , which is influenced by the defects mentioned, cannot be increased solely by making the ceramic insulator correspondingly thicker or longer. This is due to the fact that an increase in the thickness or length of the insulator does not result in a linear increase in the breakdown field strength E _bd , but rather that there is an essentially root-shaped relationship between the thickness or length of an insulator and its breakdown field strength. i.e. only a relatively small increase in the breakdown field strength can be achieved by a large increase in the thickness or length of the insulator. As a result of this root-shaped relationship between thickness and breakdown field strength, the material expansion of the insulating material or the insulating element would have to be increased disproportionately in order to achieve a significant increase in the breakdown field strength. Although this is technically possible to a certain extent, it is not economically feasible.

The object of the invention is therefore to provide an insulator arrangement for a high-voltage or medium-voltage system which, compared to the prior art, ensures an increase in the breakdown field strength of the insulator arrangement with constant geometric dimensions. From the JP 2014 182877 A a resin molded vacuum interrupter is known.

The solution to the problem consists in an insulator arrangement for a high-voltage and medium-voltage system with the features of patent claim 1.

The insulator arrangement according to the invention for a high-voltage or medium-voltage system according to patent claim 1 has at least one ceramic structural element which is designed to be axisymmetric. A typical symmetrical configuration of the structural element would be a cylinder shape, which can however also run conically; an elliptical distortion of the cross section is also technically possible in principle. In this case, the structural element has at least two ring-shaped base regions which are separated from one another by a likewise ring-shaped blocking region. Ring-shaped is understood here to mean a cylindrical shape, which can also run conically or in the form of a hollow cone, which has a circular or elliptical cross section. The invention is characterized in that the permittivity of the material of the blocking region is at least twice as high as the permittivity of the material of the base region.

By inserting blocking areas or at least one blocking area between two base areas of the insulator arrangement with a significant increase in the permittivity of the blocking area compared to the base area by at least a factor of 2, the electric field strength of the electric field induced by the high-voltage system becomes clear in the blocking areas compared to the base areas humiliated. This is referred to as weak-field areas; ideally, these are field-free areas. This field weakening is determined by the ratio of the relative permittivity of the material of the base regions and the relative permittivity of the blocking regions. This electrically subdivides the ceramic internally into short axial pieces, greatly increasing the electrical strength of the section as well as that of the entire insulator assembly.

The permittivity ε, which is also referred to as the electrical conductivity or the electrical function, is understood to mean the permeability of a material for electrical fields. The vacuum also has a permittivity that is also referred to as the electric field constant ε ₀ . The relative permittivity ε _r of a substance results from the ratio of its actual permittivity ε to the electric field constant ε ₀ : $${\mathrm{e}}_{\mathrm{right}}=\mathrm{e}/{\mathrm{e}}_0.$$

In the following, the relative permittivity ε _r described in Equation 1 is used for the permittivity.

A significant weakening of the electric field in the blocking regions can already be observed by a difference of a factor of 2 between the relative permittivities of the base region and the blocking region. In principle, however, it is true that the weakening of the electric field in the blocking areas and thus the resulting segmentation of the base areas in areas that are electrically decoupled from one another is all the stronger, the higher the relative permittivity in the blocking areas, i.e. the higher the factor between the permittivity of the blocking area and the permittivity of the base region. It has been found that it is even more advantageous if the relative permittivity of the blocking region is at least five times as high as the permittivity of the base region; it is particularly advantageous if it is at least ten times or is particularly advantageously at least 100 times as high as the permittivity of the base region.

Such a high permittivity can be achieved in particular by a titanate, ie a salt of titanic acid, in particular barium titanate. An advantageous combination is an aluminum oxide or a material that includes aluminum oxide as the material for the base area and a material based on a titanate, in particular barium titanate or calcium titanate, for the blocking area. The titanium oxide also has a high permittivity and is suitable as a material or as a material component of the blocking region.

In this case, the relative permittivity of the material of the base region is usually and preferably between 5 and 25. The relative permittivity is a unitless variable which, as stated, results from the ratio of the total permittivity and the electric field constant ε ₀ . In contrast, the relative permittivity of the material of the blocking region is at least twice as high as the relative permittivity of the base region, ie it is at least 10 and is in a range between 10 and 10,000. The relative permittivity of the control range is particularly preferably in a range between 100 and 10,000, particularly preferably between 1,000 and 10,000.

The length of the base areas in the direction of the axis of symmetry can be between a value of 5 mm and 50 mm. It has been found that particularly good segmentation of the insulator arrangement or of the structural element results in these length ranges of the base regions. The same applies to a linear expansion of the blocking areas that is between 0.1 mm and 5 mm.

The ratio of the linear extent of a respective base region to a respective Linear expansion of the associated restricted area has an amount between 10 and 100.

It is expedient for the insulator arrangement described to be part of a high-voltage or medium-voltage switchgear, which can be either a vacuum switchgear or a gas-insulated switchgear.

Furthermore, it is expedient if shielding elements are attached to an inner wall of the insulating structural element, which serve to deflect and divert the electric field and to distribute the equipotential lines more homogeneously in the material of the structural element. These shielding elements, also known as shielding plates, are preferably arranged in such a way that they are fastened in the structural element where there is a blocking area. Equipotential lines are lines with the same electrical potential. They are perpendicular to the corresponding field lines of the associated electrical field and have a comparable density. Narrow equipotential lines correspond to narrow field lines, equipotential lines drawn apart also lead to field lines drawn apart.

• Figur 1 eine Hochspannungsschaltanlagen mit einer Isolatoranordnung nach dem Stand der Technik,
• Figur 2 eine projizierte Ansicht eines isolierenden Strukturelementes mit Basisbereichen und Sperrbereichen,
• Figur 3 eine dreidimensionale Draufsicht auf das Strukturelement nach Figur 2,
• Figur 4 ein halbierter Querschnitt durch ein Strukturelement gemäß Figur 2 mit eingezeichneten Äquipotentiallinien,
• Figur 5 eine analoge Darstellung wie in Figur 4 jedoch mit zusätzlichen Schirmelementen.

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

• figure 1 a high-voltage switchgear with an insulator arrangement according to the prior art,
• figure 2 a projected view of an insulating structure element with base areas and blocking areas,
• figure 3 a three-dimensional top view of the structural element figure 2 ,
• figure 4 a halved cross-section through a structural element according to FIG figure 2 with drawn equipotential lines,
• figure 5 an analogous representation as in figure 4 but with additional screen elements.

In figure 1 a representation of a high-voltage switchgear 3 is given, which has a switch room 26 in which two switching contacts 24 are shown to be axially movable relative to one another, an electrical contact being able to be made or separated by an axial movement of at least one of the switching contacts. Furthermore, the switchgear 3 has insulator arrangements 1 which comprise at least one insulating structural element 2 . For the switchgear shown here figure 1 the insulator arrangement 1 has three structural elements 2 . In principle and preferably, however, the insulator arrangement 1 consists of only one structural element 2 if possible. The possibility of realizing this will be discussed in more detail below. In an insulator arrangement 1 according to the prior art, as a rule, a plurality of structural elements, which consist in particular of an oxide ceramic, for example aluminum oxide ceramic, are joined together to form the entire insulator arrangement 1 by means of a corresponding joining method. By joining several conventional structural elements, it is possible to achieve segmentation, which in turn leads to a higher breakdown field strength and thus to a strong increase in voltage. The length of the insulator arrangement 1 in its axial direction is determined in particular by its breakdown field strength or its maximum isolable voltage.

In figure 2 a structural element 2 is shown which has both base regions 4 and blocking regions 6 . The base areas 4 have an axial length extension 8 which is greater than an axial length extension 12 of the blocking areas 6. Two base areas 4 are separated from one another by a blocking area 6 in each case. The axial expansion is described in each case along the axis of rotation 10 . In figure 3 is the same insulating structural element 2 from the better clarity figure 2 given in a three-dimensional representation. In the Figures 4 and 5 is in each case the course of equipotential lines of equipotential lines 16 of an electric field which is induced by the electric current flow present in the switch room 26. Only the right half of the cross section of the structural element 2 is shown. The axis of symmetry 10 is located on the outer left edge, in the middle of the illustration figure 4 and also according to figure 5 a section through the base regions 4 and through the blocking regions 6 is given. In doing so, they are divided Figures 4 and 5 in each case on the left in the image in an area 18 within the structural element and in an area 22 outside of the structural element and in an area 20 which represents the section through the material of the structural element.

Starting from the axis of symmetry 10, a homogeneous electric field, which is described by the equipotential lines 16, is shown. The homogeneity of the field in area 18 is shown by the relatively even distance between the equipotential lines 16. In contrast, in area 22 outside of structural element 2, the course of the equipotential lines is very different; here there are areas with a high density of equipotential lines, in which a strong electric field prevails and an area with widely spread equipotential lines 16 in which there is a weaker electric field. It is noticeable that there are almost no equipotential lines 16 in the blocking areas 6, which means that an extremely weak electric field or, in the ideal case, no electric field prevails in the blocking areas 6. This in turn leads to electrical segmentation of the insulating structural element, ie the ceramic insulator, being produced by the blocking regions 6 . The base regions 4 thus act like further subordinate insulating structural elements which are electrically isolated from their neighboring base region are separated by the restricted area 6.

An analogous representation of this is in figure 5 given, the equipotential lines almost not occurring here in the blocking areas 6 and thus the described segmentation between base areas is achieved. figure 5 However, FIG. Corresponding screen elements 14 are also in figure 1 shown accordingly. The screen elements 14 are preferably designed in such a way that they are anchored in the blocking areas 6 in the structural element 2 .

The reduction of the equipotential lines 16 or the electric field 16 represented in this way in the blocking regions 6 of the structural element 2 is achieved in that the material of the blocking regions 6 has a relative permittivity which is at least twice as high as the relative permittivity of the base regions 4. In this way, the electric field is practically pushed out of the blocking areas 6 . This in turn causes the structure element 2 to be electrically segmented into the base regions 4 . This in turn has a similar effect on the breakdown field strength as the joining of several structural elements, as shown in figure 1 with the designation 2' for the structural element. In principle, the joining of structural elements 2 to form an insulator arrangement 1 is not desirable, since this involves cost-intensive work processes that require quality assurance and a high level of technical complexity in order to ensure vacuum tightness or gas tightness. It is thus possible through the described arrangement of the structural element 2 and the segmentation into base regions 4 and blocking regions 6 to configure the entire insulator arrangement 1, a switchgear 3 or generally a high-voltage or medium-voltage system 3 with just one insulating structural element 2. Whether this is technically sufficient also depends on the required total breakdown field strength or the maximum applied voltage. For example, high-voltage switchgear of 72 kV can be realized by a structural element 2 with a length extension in the axial direction of 80 mm or less. With the conventionally described technology, two to three structural elements would have to be joined together using a joining process. In summary, it can be said that an insulator arrangement 1 should only comprise one structural element 2, but in the case of high-voltage systems with very high voltage, two or more structural elements 2 can also be joined to form an insulator arrangement 1, in which case this then has a total length expansion that is significantly lower than the linear expansion of conventionally equipped structural elements according to the prior art without the segmentation described.

A further advantage in the manufacture of the insulator structure is that during the manufacture of the structural element 2, materials for the base regions 4 and materials for the blocking regions 6 can be introduced alternately into a compression mold and can already be pressed and sintered into this structure. i.e. A segmented structural element 2 can be produced by a conventional work step by introducing the materials alternately into the corresponding mold, which has a breakdown strength and a strength that can only be achieved using conventional means with structural elements that are connected to one another by complex soldering or joining methods. In this way, the manufacturing costs of the insulator arrangement can be significantly reduced and the claimed linear expansion and thus the installation space of the switchgear and the external dimensioning of the switchgear can be reduced.

Claims (8)

1. Insulator arrangement for a high-voltage or medium-voltage switchgear assembly (3) having at least one axially symmetrical insulating structure element (2), characterized in that the ceramic structure element (2) has at least two annular base regions (4) which are separated from one another by an annular blocking region (6), as a result of which the ceramic structure element (2) is internally subdivided in electrical terms into short axial pieces in such a way that the ratio of the length expansion (8) of a respective base region to the respective length expansion (12) of the blocking region (6) arranged therebetween is between 10 and 100, wherein the relative permittivity of the material of the blocking region (6) is at least twice as high as the relative permittivity of the material of the base regions, and wherein the length expansion (12) of the blocking region (6) in the direction of the axis of symmetry (10) is between 0.1 mm and 5 mm.
2. Insulator arrangement according to Claim 1, characterized in that the relative permittivity of the material of the blocking region (6) is at least five times, in particular ten times, in particular 100 times, as high as the relative permittivity of the base region (4).
3. Insulator arrangement according to Claim 1 or 2, characterized in that the material of the blocking region (6) comprises a titanate, in particular barium titanate.
4. Insulator arrangement according to one of Claims 1 to 3, characterized in that the material of the base region (4) has a relative permittivity which lies between 5 and 25.
5. Insulator arrangement according to one of Claims 1 to 3, characterized in that the relative permittivity of the material of the blocking region (6) is between 10 and 10,000, in particular between 100 and 10,000, in particular between 1000 and 10,000.
6. Insulator arrangement according to one of the preceding claims, characterized in that the length expansion (8) of the base regions (4) in the direction of the axis of symmetry (10) is between 5 mm and 50 mm.
7. Insulator arrangement according to Claim 1, characterized in that shielding elements (14) are fitted on an inner wall (28) of the structure element (2).
8. Insulator arrangement according to Claim 7, characterized in that the shielding elements (14) are arranged in or on a blocking region (6).

Images