EP4016576A1 - Electrical switching device for medium and / or high voltage applications - Google Patents

Abstract

The invention relates to an electrical switching device, in particular for medium and/or high voltage applications, having at least two contactable conductor elements that can be spaced apart by a movement device and a housing that defines a switching chamber and is made of an insulator and two metal caps that seal the housing axially. The invention proposes for the first time to apply a coating with a high permittivity or one that is high relative to the ambient air, made of a plastic, in particular a filled plastic, in whole or in part, on the housing surface of a vacuum interrupter, so that the field lines are broken at critical points, in particular at triple points, and arcs so far be prevented as possible.

Description

The invention relates to an electrical switching device, in particular for medium and/or high voltage applications, having at least two contactable conductor elements which can be spaced apart via a movement device and a housing which is made of one or more insulators and defines a switching chamber, parts of the switching chamber being able to be made of metal. usually in the vicinity of the contact gap and two, preferably metal, caps that close off the housing axially.

In the case of medium and/or high voltage applications, generally speaking at voltages greater than 1 kV, the high voltages require more complex switching devices that can withstand the electrical fields that occur, are as resistant as possible to degradation effects and also flashovers outside of the actual switching chamber should avoid.

A classic example of this are the vacuum circuit breakers (VCBs), which are core components in power transmission and distribution, particularly in their switching systems. They cover a large part of medium-voltage switching applications, i.e. switching applications in the range from 1 kV to 52 kV, for example, as well as a relevant part in low-voltage systems. Their use in high-voltage transmission systems, for example at voltages greater than 52 kV, is also increasing. While a VCB is closed most of the time, meaning that the conductor elements are contacted, its main task is to interrupt currents in AC systems under nominal conditions, i.e. in particular to switch nominal currents on and off, or preferably to interrupt currents under fault conditions , especially short circuits to interrupt and protect the system. Other applications include pure switching of load currents using contacting conductor elements, mostly used in low and medium voltage systems.

The vacuum interrupter (VI, also vacuum interrupter) is the core element of a VCB. A vacuum interrupter usually has a pair of contacts which are formed by corresponding conductor elements, at least one of which can be moved by means of a movement device in order to be able to bring about the open and closed states of the switching device. Usually, one conductor element is moved axially with respect to the other fixed conductor element. The contacts may be fabricated from conductive bolts, particularly metal, which provide both electrical and thermal conduction and the mechanical means to hold and/or move the contacts.

A VI also comprises a vacuum-tight housing and the aforementioned movement device and can also comprise a metal bellows which is connected to the housing on one side and to the moving conductor element, in particular the moving bolt, on the other side. The housing is essentially formed by an insulating component, i.e. an insulator, for example a ceramic tube, which is connected to the conductor elements via connecting elements, metal caps or the like being used, for example, which close the insulating component in the axial direction to form the switching chamber . Inside the switching chamber there is a permanent high vacuum of less than 10^-4 hPa or 10^-4 mbar. The vacuum is necessary to ensure the "make-break" operations and to ensure the isolation properties of the switching device in the open state.

When the switching device is in an open state, it is necessary to isolate the rated voltage of the system as well as high amplitude transient voltages such as be triggered by lightning striking the system. When the switching device changes from the closed to the open state, thus spacing the contacts of the conductor elements, rated currents or short-circuit currents must be interrupted, which lead to the appearance of transient voltage spikes across the VI that are significantly higher than the AC voltage ratings of the system.

High voltages in vacuum systems usually generate free electrons through field emission processes when the electric field strength is sufficiently high. The acceleration of the electrons in the high electric fields increases the kinetic energy of these electrons, for example up to energies exceeding tens or even hundreds of KeV. The interaction of these high-energy electrons with the housing structures leads to the production of high-energy X-rays that can exit the vacuum interrupter. While under normal conditions the fault current within the vacuum interrupter is minimal and does not produce any appreciable X-ray radiation, circumstances can arise, for example when transient voltage spikes of high amplitude occur, in which the resulting X-ray radiation produces free electrons on and/or near the outer surface of the insulator. These electrons can be accelerated by the electric fields on and near the insulator surface, disturbing the electric field distribution in sensitive areas and leading to gas breakdown, resulting in failure of the vacuum interrupter operation.

Even in cases where there is no detectable X-ray emission, for example in low and medium voltage applications, the high electric fields in critical areas of the vacuum interrupter, for example at the connection of the insulator and the metal caps by soldering (brazing), can lead to the ejection of electrons, resulting in an appreciable amount of field emission. These electrons can also locally disturb the electric field and lead to further Field amplification and/or charge multiplication due to electron avalanches, which in turn can result in the loss of insulation strength and/or the voltage resistance of the vacuum interrupter.

Similar challenges exist on the inner surfaces of the vacuum interrupter, while an additional problem must be solved. Due to the interruption of the current (rated current as well as short-circuit current), parts of the contact material are vaporized and distributed as hot metal vapor within the switching chamber. This metal vapor can settle on the insulator surface and over time builds up a conductive metal layer. This metal layer, even if it is only slightly conductive, can also disturb the electric field outside and inside the vacuum interrupter and thus degrade the voltage withstand capability of the vacuum interrupter over time. In this context, it was proposed that a shielding element, which can also be made of metal, be provided in the contact area of the conductor elements to intercept free metal particles of the conductor elements, but this also has an influence on the field distribution within the switching chamber, but also on the insulator.

For the above reasons, the housing of the interrupter, and in particular the insulator, which is usually made of ceramic, must be able to withstand high voltages across the relevant surface, even in the presence of X-rays and free electrons, or, in some cases, even when the insulator is contaminated by dust particles electrostatically attached to the outer surface of the insulator. Since the insulator contributes significantly to the cost of a vacuum interrupter (or other switching device) and also negatively affects the cost of other structural elements of the vacuum interrupter (or other switching device), it is necessary to optimize the housing for maximum dielectric strength with minimum component size.

So far, this problem has been solved by selecting the inner and outer geometry of the vacuum interrupter in such a way that the expected electric field strengths do not exceed empirically derived limits for a specific geometry of the vacuum interrupter. Since these limitations cannot be precisely predicted, particularly for triple point regions and/or sharp metal edges, the design of vacuum interrupters not only depends on electric field calculations during the design process, but also requires a large amount of empirical optimization. This also relates to the build-up of metallic layers on the inner surfaces of the insulator, which, as already mentioned, are usually to be avoided today by using shielding structures (shielding elements) within the switching chamber. However, nowadays the deposits of the metal vapor and their influence on the dielectric strength of the vacuum interrupter VI cannot be quantitatively predicted in a sufficiently accurate way.

It should also be noted that the design processes mentioned all result in a reduction of the insulating properties of the vacuum interrupter's outer structure well below the dielectric strength of air or other gases surrounding the vacuum interrupter, so that housing and/or insulator sizes - in terms of length and/or or the diameter - are required, which are not optimal in terms of costs and space. The addition of shielding elements relative to the metal vapors introduces distortions into the operational electric fields at the insulator, which can result in strong fields at certain locations and consequent overloading of the insulator caused by charges building up there. However, other causes also lead to such high local fields on the insulator of the housing of the vacuum interrupter, as has already been explained, with the problems presented here also applying to other switching devices, such as gas switches, in addition to the vacuum interrupter mentioned by way of example.

As a rule, the well-known VIs are often built symmetrically to an - imagined - center plane of the tube in order to minimize the number of different components and the complexity of the structure. However, the real environment of the tube generally strongly distorts the electric field, so that areas of the tube are strongly electric - in the sense of a high mean electric field strength.

There is therefore a need to meet the different requirements for dielectric strength, such as high lightning impulse voltages with strong transient switching edges - for example 1.2µm rise time and an exponentially falling trailing edge with a time constant of 50ps, nominal voltages of 50Hz or 60Hz fundamental frequency with harmonic components up to the kHz range, as well as the so-called nominal withstand voltage of 50/60Hz at up to twice the nominal voltage amplitude, for a load duration of up to one minute, through the design of the switching device.

It is therefore the object of the present invention to specify a switching device with a - preferably cylindrical - housing comprising an insulator and axial end caps, which has increased dielectric strength with a minimal overall size and manufacturing costs of the switching device, in particular a switching device that is used particularly in the heavily electrically loaded Areas - as explained above - the housing shows improved dielectric strength.

This object is solved by the subject matter of the present invention as disclosed in the description, the figures and the claims.

Accordingly, the subject of the present invention is an electrical switching device with at least two contactable conductor elements that can be spaced apart via a movement device and a housing that defines a switching chamber and that at least partially surrounds the conductor elements. wherein the housing has an insulator body and areas of an electrical contact and wherein the housing has at least partially a refractive-control coating on the outside, which has a dielectrically insulating matrix, optionally containing filler, with a permittivity ε _r >/=2.

"Permittivity" refers to the ability of a material to polarize through electric fields. Permittivity is a material property of electrically insulating polar or non-polar compounds that only becomes apparent when these compounds are exposed to an electric field.

The matrix material can be selected from the group consisting of elastomers, duroplastics, thermoplastics and/or glass. The various coating methods for producing the coating can be selected accordingly.

The matrix material is preferably applied as a paint, in particular in the form of a wet paint or powder paint. Other application methods, such as spraying, immersion, potting, etc. are conceivable, but they are not in the foreground given the current state of research into the technology.

A major advantage of application as a powder paint and/or wet paint is that the refractive-controlling coating produced is free of pores. Although this type of freedom from pores is also obtained by encapsulation, the homogeneity of the coating generally suffers, particularly at the edges.

When applied as a wet paint, this usually includes solvents that are not present in the matrix material or are only present in small amounts after the paint has dried.

According to an advantageous embodiment, the matrix consists of a polymeric matrix material, for example a polymeric resin, which is present in the form of a polymeric binder.

A polymer or a polymeric binder is referred to as a "polymeric matrix". The polymeric matrix includes in particular a resin or a resin mixture, such as epoxy resin, silicone elastomer, siloxane resin, silicone resin, polyvinyl alcohol, polyester imide and similar duroplastic, thermoplastic plastics, as well as any combinations, copolymers, blends and mixtures of the above resins and/or plastics. The polymeric matrix can be filled or unfilled as a coating with a permittivity of ε _r >/=2.

The matrix preferably contains fillers with a high permittivity compared to air, in particular refractive-dielectrically insulating fillers, such as ceramic fillers, which are polar and/or easily polarizable in an electric field.

The materials for the filler(s) are preferably selected from class 1 ceramic materials, which meet high stability requirements and whose permittivities have a low dependence on temperature and field strength. These include, for example, compounds such as selected titanates, which show reproducibly low temperature coefficients and low dielectric losses. Their permittivity is largely independent of the field strength, which has advantages for the application under discussion here.

The ceramic materials particularly suitable here for the filler(s) have relative permittivities ε _r in the range from
ε _r >/= 2 to ε _r </= 200, preferably from
ε _r >/= 10 to ε _r </= 100.

Fillers made of a material which is commercially available from the field of capacitor ceramics and is therefore comparatively inexpensive and available in sufficient quantities are preferred. In particular, the materials come into consideration that have an almost linear temperature profile of the capacitor capacitance demonstrate. For example, these are in the form of one or more ceramic(s), in particular ceramic(s) with metal nitride, metal carbide, metal boride and/or metal oxides such as titanium dioxide, aluminum oxide, ceramics comprising selected compounds of titanate are also suitable because of their field strength-independent permittivity. In addition to mixed oxides, such as titanate and/or mixtures of different metal oxides, oxides of metal alloys in any combination with all of the above-mentioned materials are particularly suitable for fillers that exhibit largely field strength-independent permittivity.

For example, a mixture of finely ground paraelectrics such as titanium dioxide with admixtures of magnesium (Mg), zinc (Zn), zirconium (Zr), niobium (Nb), tantalum (Ta), cobalt (Co) and/or Suitable for strontium (Sr). The following compounds are mentioned here as examples: MgNb ₂ O ₆ , ZnNb ₂ O ₆ , MgTa ₂ C> ₆ , ZnTa ₂ O ₆ , such as (ZnMg)TiO ₃ , (ZrSn)TiO ₄ and/or Ba ₂ Ti ₉ O ₂₀ , and any combinations and mixtures of the compounds mentioned.

When applied in the form of a powder coating, customary additives such as hardeners, accelerators and/or additives may be present in the amounts conventionally recognized as advantageous. Both duroplastics and thermoplastics can be applied in the form of a powder coating.

A hardener is present when additive polymerisation takes place. An accelerator, initiator and/or catalyst is used in all instances where resin is cured.

The matrix material is usually applied before, during, but preferably after the manufacture of the housing. For example, the refractive-control layer, which is produced by coating with the matrix material, by spraying, doctoring, dipping, brushing and / or other methods, the production of a thin homogeneous - in particular as homogeneous as possible and as non-porous as possible - allow coating applied.

The application method is preferably carried out automatically.

The refractive-controlling coating is preferably a filled coating of one or more matrix materials, which can be organic, for example in the form of a polymer, or inorganic, for example as glass, in which the filler is introduced.

The amount of filler in the refractive control coating can vary within wide limits. A filler concentration of 1% by volume - i.e. the almost unfilled matrix material with a relatively low refraction, which is almost exclusively caused by the dielectric barrier that forms the matrix material - can be present in the coating up to a filling of 70% by volume. The preferred range for the amount of filler is between 20 and 60% by volume, in particular from 30% by volume to 40% by volume, of filling in the matrix material.

The filler particles of the refractive control coating do not have a preferred shape, they can be embedded in the matrix in any shape and size. For example, the filler particles are irregular after appropriate grinding.

Filled paints, whose particles are as close as possible to a spherical shape, are better suited for processing than other shapes, because the specific surface area is the lowest and the lowest possible processing viscosity is achieved with the same degree of filling.

The size of the fillers may vary. Different filler fractions can be present in the filler. The housing can be provided with differently filled coatings in different areas.

With thicker coatings and/or with certain material combinations, the field lines are broken more than with others. The level of the permittivity and the thickness of the applied refractive-controlling coating determine how much the electric field is equalized.

Within the scope of the present invention, thicknesses of the refractive-controlling coating of 10 μm to 5 mm, preferably in the range between 100 μm and 3 mm, particularly preferably in the range between 500 μm and 2 mm, have proven to be expedient.

In the present case, the permittivity of the coating is used according to one embodiment of the invention—filled or unfilled—so that the electric field on the surface of the housing of the switching chamber is pushed away by the increased permittivity compared to the uncoated surface, thus reducing local field overshoots. This is explained again in FIG. 2 and shown schematically.

Without the refractive control layer, an insulating gas such as nitrogen, air, or sulfur hexafluoride would typically be present at the surface of the housing. All these gases have a comparatively small permittivity. Air, for example, has the permittivity ε _r = 1.00059. A coating made of a plastic such as a resin, on the other hand, has a permittivity of at least twice the value ε _r = 2 - example silicone resin - up to about ε _r = 9 - example polyvinyl alcohol. This refers to the cured resins.

The refractive-control coating proposed here breaks the exiting field lines according to the refractive field control - refraction = refraction - because the field displacement from the material with a higher dielectric constant to the material with a lower dielectric constant makes it more difficult for the field to penetrate into the higher permittivity, since the electric field is pushed away from the edge or triple point.

The triple point, for example, is the area of the housing in which a metal electrode, a solid insulator and a gaseous insulator - in this case the surrounding gas - come together.

According to an advantageous embodiment, the refractive-controlling coating is applied at least partially to at least one of the contacting sides of the housing. This is particularly so because the refractive-controlling coating is also a dielectric barrier that, applied to the metal electrodes, ensures that electrons have a much harder time escaping from the metal. Or, in other words, the electrical flashover between the electrodes is shifted to higher voltages by the dielectric barrier. Due to the refractive field shift then again in addition to even higher voltages.

The refractive-controlling coating is preferably provided on both metallic caps of the housing, which axially close off the—preferably cylindrical—insulator body to form the switching chamber, in whole or in part in addition to being applied to the insulator body.

The refractive control coating thus covers the housing in whole or in part or in selected areas. The refractive-controlling coating is applied, for example, directly to the housing surface or, for example, to a lower layer, such as a resistive layer after the EP 3146551 B1 .

A lower layer, on which the refractive-controlling coating is applied, can be both a further refractive-controlling layer and another, in particular a resistive layer after the EP 3146551 B1 , but preferred also, deviating from this, a resistive-capacitive layer.

The lower layer is preferably a thinner layer than the upper one, so that the layer thicknesses increase from the inside to the outside on the outer surface of the housing.

In the case of a coating on a resistive lower layer, provision is made in particular for the matrix materials of the respective coatings to be compatible with one another. It is preferred, for example, that the matrix materials are at least mutually inert, but advantageously they can be mixed with one another and/or in one another as desired. It is very preferred that the matrix materials of different layers - ie, for example, the matrix material of a refractive control coating according to an embodiment of the present invention and the matrix material of a resistive coating according to the EP 3146551 B1 - have the same or similar chemical composition.

The coatings can also be provided combined in the form of layer stacks, with a resistive coating according to the EP 3146551 B1 is preferably provided on the insulating areas of the housing of the switching device, such as on a ceramic cylinder, whereas the refractively controlling coating is provided in particular on the caps of the housing, ie the contacting areas. However, both coatings can extend over one another as desired and in particular also over all areas of the housing on the outside.

All layers of the overall coating of the housing fully or partially cover the respective parts of the housing, but on the outside.

The embodiments in which the refractive-controlling coating is not applied over the entire surface of the housing may be mentioned here as being particularly suitable. but only partially covers the housing. In this case, it is particularly preferred if the refractive-controlling coating is applied to the caps, in particular to the metal caps and/or to the edges that form the caps with the insulator body.

Here again, it is particularly preferred that the refractive-controlling coating also extends—forming an edge—beyond the edge, for example also onto the surface of the insulator body.

In this case, it is irrelevant whether the insulator body itself is still coated, for example provided with a resistive coating, or not.

• dass die untere - resistive Schicht komplett das ganze Gehäuse bedeckt und die obere refraktiv-steuernde Schicht die untere Schicht nur teilweise abdeckt;
• dass die untere Schicht die Gehäuse-Außenoberfläche nur teilweise bedeckt, insbesondere dass die untere Schicht in Form einer resistiv-kapazitiven Schicht aufgebracht ist und die obere refraktiv-steuernde Schicht die untere Schicht und die gesamte Gehäuse-Außenoberfläche ganz oder teilweise bedeckt;
• dass die untere Schicht teilweise von der oberen Schicht unbedeckt bleibt;
• dass resistiv-kapazitive Bereiche der unteren Schicht mit der refraktiv-steuernden oberen Schicht abgedeckt sind;
• dass zwei oder mehr Schichten einer Art verschiedene Gehäusebereiche bedecken und sich dabei eine oder keine Überlappung ergibt;
• etc...

There are all possible layer combinations of coatings on the housing, in particular of coatings of the resistive coating in question here after EP 3146551 B1 on the one hand and a refractive-controlling coating according to an embodiment of the present invention on the other hand conceivable, for example

• that the lower - resistive layer completely covers the whole housing and the upper refractive-controlling layer only partially covers the lower layer;
• that the lower layer only partially covers the outer surface of the housing, in particular that the lower layer is applied in the form of a resistive-capacitive layer and the upper refractive-controlling layer completely or partially covers the lower layer and the entire outer surface of the housing;
• that the bottom layer remains partially uncovered by the top layer;
• that resistive-capacitive areas of the lower layer are covered with the refractive-controlling upper layer;
• that two or more layers of a species cover different areas of the housing with some or no overlap;
• Etc...

According to that EP 3146551 B1 if the resistive layer is applied over the entire surface of the outer surface of the housing, according to the present invention it can, in contrast, also only partially cover the outside of the housing, in particular it can also be in the form of a resistive-capacitive layer with a non-galvanic - i.e. not via a contact - be applied electrically conductively connected area.

In principle, it is advantageous if the lower layer is thinner than the upper layer.

In principle, it is advantageous if the refractive-controlling layer lies on the resistive layer.

• Figur 1 zeigt eine Schaltvorrichtung nach einer Ausführungsform der vorliegenden Erfindung als Vakuumröhre und
• Figur 2 zeigt schematisch die Wirkung einer refraktiv steuernden Beschichtung auf einer Gehäuse-Oberfläche eines Gehäuses einer Schaltvorrichtung nach einer beispielhaften Ausführungsform der Erfindung.

A switching device according to the present invention is in figure 1 shown.

• figure 1 12 shows a switching device according to an embodiment of the present invention as a vacuum tube and
• figure 2 12 schematically shows the effect of a refractive control coating on a housing surface of a housing of a switching device according to an exemplary embodiment of the invention.

figure 1 shows an embodiment of a switching device 1 according to the invention, here a vacuum interrupter, in the form of a basic sketch. A housing 3 composed here of two tubular ceramic parts, i.e. insulator bodies 2, is closed by metal caps 4, which form areas with electrical contacts, and defines a switching chamber 5, into which two conductor elements 6, designed for example as bolts, with contacts 7 are guided.

This in 1 The lower one of the conductor elements 6 is designed to be movable according to the arrow 8 and the indicated movement device 9 and can be displaced in the direction of extension 10 of the conductor elements 6, which also forms the axis of symmetry of the switching device 1, in order to bring the contacts 7 into contact or space them apart, whereby presently an open, so spaced state of the switching device 1 is shown. Due to the mobility of the lower conductor element 6, this is coupled to the metal cap 4 via a metal bellows 11; the metal caps 4 are conductively connected to the conductor elements 6 on both sides.

Inside the switching chamber 5 there is a vacuum, in this case with a pressure of <10 ^-4 hPa.

However, the invention also relates to gas switches where the gas is inside the switches. The gas circuit breakers also included here mean those in which gas serves as the switching medium on the one hand and - after successful disconnection - as the insulating medium on the other. Usually SF6 is used nowadays. Since SF6 is to be replaced as a strong greenhouse gas, switches with CO2, fluoronitrile or other alternative gases are also conceivable in the future.

In order, for example, to prevent metal vapors produced when switching device 1 is opened from reaching the inner surface of insulator 2, here ceramic, a metal shielding element 12 (vapour shield) is provided in the contacting area in switching chamber 5. However, this shielding element 12 also causes a distortion of the electric field, so that in an area behind the shielding elements there would be a lower electric field during operation than in the "unshielded" areas, where charges can accumulate, for example, and thus can provide further field distortions that could call into question the functionality of the switching device 1.

In order to counteract this, it is provided in the exemplary embodiment outlined here that a refractive-controlling coating 13 according to a Embodiment of the invention is located.

The refractive-controlling and - here over the entire surface - applied coating 13 of the embodiment shown here comprises a polymer matrix which is filled with a high-permittivity filler made of a ceramic material ε _r in the range of greater than/equal to 2 to 200, preferably from 10 to 100 , is filled. The matrix contains 30% by volume of the filler. It is a mixture of titanium dioxide and aluminum oxide particles.

The refractive-controlling coating 13 is relatively inexpensive in terms of material price and can be sprayed on relatively easily—also automatically. Their presence can be detected relatively easily using a scanning electron microscope and elemental analysis.

the figure 2 shows schematically the effect of a refractive control coating on a housing outer surface like that in figure 1 housing 3 shown.

figure 2 shows schematically the course of the field and equipotential lines 15, 14 at each triple point, right half with a refractive-controlling coating 13 and left for comparison without such a coating, according to the prior art. As can be seen, the field lines 15 on the left run unbroken from the metal cap 4 into the surrounding gas, eg air. This can result in lightning discharges 16 . On the right, where the coating 13 lies between the metal cap 4 and the ambient air, the field lines 15 are broken at the transition from the coating with high permittivity into the surrounding air with low permittivity - see area 17 - thereby both the equipotential lines 14 and the field lines 15 far apart, so that no arcs occur.

The length of the housing 3 of a switching device 1 can be reduced by the refractive-controlling coating 13, as proposed for this application for the first time, and thus the overall length of the electrical switching device 1. This saves material costs. For example, a housing 3 could be manufactured for a specific voltage level. Exactly this housing 3 could then be coated with the refractively controlling coating 13 according to an embodiment of the present invention, and thus be usable for the next higher voltage level. In terms of process technology, this results in a design that can be used for two voltage levels, with the same two housings 3 being usable for two switching devices 1 of different voltage levels!

The only difference between the two housings is the additional refractive control coating 13.

The special advantage of the use of a refractive-controlling coating, which is presented here for the first time, is that because hardly any current flows through this coating, it is very resistant to aging and lasts longer and more reliably.

The invention proposes for the first time a coating with high permittivity or at least high relative to the ambient air ε _r = 1 made of a plastic ε _r >/= 2, in particular ε _r >/= 3, in particular a filled plastic, on the housing surface of a vacuum interrupter entirely or partially applied so that in critical areas, especially at triple points, the field lines are broken and arcs are drawn apart as much as possible, thus preventing lightning.

The present invention is not limited to vacuum tubes, but relates to other switches, for example gas-insulated switches—for example those with SF6 and/or clean air—as the switching gas. In the case of gas switches with clean air, this is usually only used as an insulating medium and is not located in the interrupter unit, where the arc occurs and the switching operation takes place.

Reference List

1

switching device

2

insulator

3

Housing

4

cap

5

switching chamber

6

ladder element

7

Contact

8th

Arrow

9

moving device

10

direction of extension

11

metal bellows

12

screen element

13

refractive control coating

14

equipotential lines

15

field lines

16

lightning

17

Area in which field lines are broken refractively

Claims (18)

Electrical switching device (1) with at least two contactable conductor elements (6) that can be spaced apart via a movement device (9) and a housing (3) that defines a switching chamber (5) and at least partially surrounds the conductor elements (6), the housing ( 3) has an insulator body (2) and areas of an electrical contact (4) and wherein the housing (3) has at least partially a refractive-controlling coating (13) on the outside, which has a dielectrically insulating matrix made of a material with a permittivity ε _r >/ = 2 includes. Switching device according to claim 1, wherein the matrix of the refractive-controlling coating (13) is present containing filler. Switching device according to one of the preceding claims, in which the refractive-controlling coating is present at least in a region of an electrical contact (4). Switching device according to claim 1, wherein the material of the filler particles of the at least one filler fraction is a ceramic with a permittivity ε _r >/= 3 and ε _r </= 200. Switching device according to one of the preceding claims, wherein the material of the filler particles of the at least one filler fraction comprises a ceramic with at least one metal oxide, a metal mixed oxide and/or a titanate. A switching device as claimed in any one of the preceding claims, wherein the total amount of filler particles in the matrix is in the range from 1% to 70% by volume. Switching device according to one of the preceding claims, wherein the resin is selected from the group of elastomers, thermosets, thermoplastics and/or glass. Switching device according to one of the preceding claims, in which the matrix is a polymeric resin and/or a polymeric resin mixture. Switching device according to one of the preceding claims, wherein the polymeric resin or the polymeric resin mixture comprises at least one compound selected from the group consisting of the following compounds: epoxy resin, silicone elastomer, siloxane resin, silicone resin, polyvinyl alcohol, polyesterimide, and any mixtures and/or combinations of the above compounds. Switching device according to one of the preceding claims, in which the refractive-controlling coating is provided in combination with at least one further coating on the outer surface of the housing (13). Switching device according to claim 10, wherein the further coating is a resistive coating. Switching device according to one of the preceding claims, wherein the resistive coating completely or partially covers the outer surface of the housing. Switching device according to one of the preceding claims, the refractive-controlling coating (13) is provided at least partly over the resistive coating. Switching device according to one of the preceding claims, in which the refractive-control coating has a layer thickness of less than or equal to 5 mm. Switching device according to one of the preceding claims, wherein the refractive control coating is present with a layer thickness of less than or equal to 2 mm. Switching device according to one of the preceding claims, wherein the refractive control coating can be applied as a wet paint. Switching device according to one of the preceding claims, in which the refractive-controlling coating can be applied as a powder coating. Switching device according to one of the preceding claims, wherein the switching device is a vacuum switch or a gas switch.

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