WO2015039918A1

WO2015039918A1 - High-voltage circuit breaker with improved robustness

Info

Publication number: WO2015039918A1
Application number: PCT/EP2014/069118
Authority: WO
Inventors: Helmut Heiermeier; Henrik Dahlgren; Timothy Sutherland
Original assignee: Abb Technology Ag
Priority date: 2013-09-18
Filing date: 2014-09-09
Publication date: 2015-03-26

Abstract

A gas insulated high voltage circuit breaker (1) comprises: a first arcing contact (31) and a second arcing contact (41), wherein at least one of the two arcing contacts (31, 41) is axially movable along an axis (A-A'); and a nozzle (32) surrounding an axially extending channel (33), wherein during a breaking operation, an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel (33), wherein at least a part of an inner surface of the nozzle (32) is coated with a first ceramic coating (34) in order to protect it from an influence of the arc.

Description

HIGH- VOLTAGE CIRCUIT BREAKER WITH

IMPROVED ROBUSTNESS

BACKGROUND OF THE INVENTION

[0001] The subject matter described herein relates generally to a gas-insulated high- voltage circuit breaker, and more particularly, to a circuit breaker wherein certain parts were treated to increase robustness and quality.

[0002] The increase in size of electrical power transmission networks experienced over the last decades has resulted in an increase of the maximum interruption current (also referred to as short-circuit current) that a circuit breaker can safely interrupt. In particular, high-voltage circuit breakers (i.e. suitable for high-voltage applications) based on gas insulation are known for their capacity to safely interrupt high currents between the contacts of the circuit breaker. In gas-insulated circuit breakers, a gas, such as sulfur hexafluoride, is used for extinguishing the arc generated when a current is interrupted. Thereby, during interruption, an electric arc develops between the arcing contacts, wherein the geometric region in which the arc develops is typically surrounded by an insulating nozzle. This nozzle often comprises PTFE and is integrally connected with the first arcing contact. PTFE typically provides a significant resistance against corrosion caused by the electrical arc and the plasma developing in the arcing region. The nozzle typically serves for guiding a gas stream for extinguishing or blowing off the arc.

[0003] In double movement breakers, the action for moving one of the two arcing contacts is transmitted via a mechanism or auxiliary transmission to the other arcing contact, such that the retracting movement of a first arcing contact is accompanied by a simultaneous or time-coordinated retracting movement of the second arcing contact. Typically, an external driving mechanism is actuating only one of the arcing contacts, and the driving movement is transmitted via the mechanical mechanism to the second arcing contact. [0004] In breakers using such a double movement system, the kinetic transfer of the force from a first moving arcing contact to a second moving arcing contact, which usually has a pin shape, is preferably achieved by employing the insulating nozzle as a force transmitting element. As the nozzle typically comprises PTFE, this poses a potential problem for using the nozzle as a force transmitter, as PTFE has generally far less mechanical stability than, e.g., metals. In order to obtain a decent and stable force transfer without any deformation in the kinetic chain, a metal portion, respectively metallic ring portion, attached to the insulating nozzle is often applied. Usually, this so called nozzle ring is made using an aluminium material in order to save weight. It is attached to an end portion of the insulating nozzle.

[0005] This nozzle ring is typically designed in order to combine different functions: Transfer of the force, guiding the exhaust gas as an elongated portion of the nozzle throat, and electrical shielding and equalizing of the electrical field. However, the metallic ring may also cause problems in conjunction with the hot plasma and the arc nearby.

[0006] The invention starts from DE 10 2006 034 742 Al, which discloses an insulating nozzle made of a first less-arc-resistant material (PTFE) and having a coating made of a second more-arc-resistant ceramic material in a heating channel region.

BRIEF DESCRIPTION OF THE INVENTION

[0007] Thus, it is an objective of the present invention to provide a more robust circuit breaker. This task is solved by the circuit breaker of the independent claims. Embodiments are given by dependent claims and each of their combinations and also in the description and figures.

[0008] In a first alternative aspect, the gas-insulated high voltage circuit breaker comprises: a first arcing contact and a second arcing contact, wherein at least one of the two arcing contacts is axially movable along an axis; a nozzle surrounding an axially extending channel, wherein during a breaking operation an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel; wherein further the nozzle comprises at least one metallic ring portion, which is located at an end of the nozzle and is coated with a first ceramic coating to protect it (i.e. the nozzle and, in particular, the metallic ring portion) from an influence of the arc. [0009] In embodiments, at least a part of an inner surface of the nozzle is coated with the first ceramic coating in order to protect the nozzle from an influence of the arc. In particular, the metallic ring portion forms part of the nozzle, and more particularly of the inner surface of the nozzle. [0010] In embodiments, the inner surface of the nozzle is fully coated with the first ceramic coating; and/or the inner surface of the nozzle is facing towards the axially extending channel.

[0011] In a second alternative aspect, the gas-insulated high voltage circuit breaker (1) comprises: a first arcing contact (31) and a second arcing contact (41), wherein at least one of the two arcing contacts (31, 41) is axially movable along an axis (A- A'); a nozzle (32) surrounding an axially extending channel (33), wherein during a breaking operation an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel (33); and wherein the high voltage circuit breaker further comprises at least one metallic shielding element located in a region radially outwards from the nozzle, wherein the shielding element is coated with a second ceramic coating in order to avoid particles from being expelled from the shielding element by a high electric field during operation of the circuit breaker.

[0012] In embodiments, the the metallic shielding element is part of the nozzle, or the metallic shielding element (62) is part of the metallic ring portion (60) or is mounted to the metallic ring portion.

[0013] A third alternative aspect of the invention disclosed herein includes a gas- insulated high voltage circuit breaker, which comprises a first arcing contact and a second arcing contact, wherein at least one of the two arcing contacts is axially movable along an axis; a nozzle surrounding an axially extending channel, wherein during a breaking operation, an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel, wherein at least a part of an inner surface of the nozzle is coated with a first ceramic coating in order to protect it from an influence of the arc.

[0014] Thereby in all these alternative aspects of the invention, at least a part of the nozzle, in particular the metal ring portion located at the end of the nozzle and/or the metallic shield element located at an outer side of the nozzle, is or are coated with a ceramic coating to protect the nozzle or part of the nozzle from damage, including damage by hot gases and/or damage induced by high-electric-field stress.

[0015] In a fourth alternative aspect or embodiment relating to the other aspects of the invention, the gas-insulated high voltage circuit breaker comprises: a first arcing contact and a second arcing contact, wherein at least one of the two arcing contacts is axially movable along an axis (A-A'); a first nominal contact and a second nominal contact, wherein at least one of the two nominal contacts is axially movable along an axis (A- A'); a nozzle surrounding an axially extending channel, wherein during a breaking operation, an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel; and wherein an end portion of at least one of the nominal contacts is coated with a third ceramic coating.

[0016] Thereby, in particular in the first and third alternative aspects of the invention, a part of the nozzle is protected from erosion due to hot gases. This is achieved by a ceramic coating of the nozzle throat or in general channel, and in particular by the first ceramic coating applied to an inner surface of the nozzle and preferably to the at least one metallic ring portion located at an end of the nozzle (i.e. located on an inner surface of the end of the nozzle). The ceramic coating is lightweight and thus does not add additional weight to the part, but makes it resistant against the arc and hot gases. A similar coating is used in embodiments (i.e. of all alternative aspects of the invention) to coat highly field stressed areas, in particular of the nozzle ring or nozzle shielding or nominal contact, in order to avoid that metallic particles from the commutation arc can hook up, in particular to the nozzle ring or nozzle shielding or nominal contact, respectively.

[0017] An additional advantage of the ceramic coating, i.e. the first ceramic coating on an inner surface of the nozzle and/or the second ceramic coating on an outer side or face of the nozzle and/or the third coating on an end portion of at least one nominal contact, is the fact that this coated surface prevents the emission of electrons even when highly stressed by electrical fields.

[0018] Further aspects, advantages and features of the present invention are apparent from the dependent claims, claim combinations, the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] A full and enabling disclosure, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein:

[0020] Fig. 1 to 3 show schematic cross-sectional views of a gas-insulated high- voltage circuit breaker according to embodiments, in different states of operation;

[0021] Fig. 4 is a schematic detailed cross-sectional view of a nozzle portion of a gas- insulated high- voltage circuit breaker according to embodiments.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet further embodiments. It is intended that the present disclosure includes such modifications and variations.

[0023] As used herein, an electrical contact through which the nominal current passes, is called a main contact or nominal contact, and the combination of a main contact and an arcing contact is called henceforth "breaker contact", and in particular "moving contact". The circuit breaker typically comprises two breaker contacts or moving contacts, each comprising a main contact and an arcing contact.

[0024] The embodiments described herein include a gas-insulated high-voltage circuit breaker for interrupting a current between a first breaker contact and a second breaker contact. The breaker contacts are typically adapted for electrically interconnecting the circuit breaker to the electrical circuit to be protected. According to embodiments herein, a high voltage is a voltage of at least about 70 kV or higher. As used in this specification and the claims, a high- voltage circuit breaker is a circuit breaker rated to a nominal voltage of at least about 70 kV or higher. [0025] In a gas circuit breaker, the arc-extinguishing medium comprises a gas. Typically, the circuit breaker includes an encapsulating case which defines a volume for the gas. Furthermore, the circuit breaker typically includes a gas blast system configured to extinguish an arc formed between a first arcing contact and a second arcing contact of the circuit breaker during a stage of the current interuption operation.

[0026] Within the following description of the drawings, the same reference numbers refer to the same components. Generally, only the differences with respect to the individual embodiments are described.

[0027] A circuit breaker 1 according to embodiments, for high or medium voltages, is shown in Fig. 1. The circuit breaker 1 comprises a circuit-breaking chamber or volume 2 that can be filled with a dielectric gas, such as in embodiments SF₆ or SF₆ and its known mixtures, such as N₂ or CF₄. In further embodiments, also other insulating or arc-extinguishing gases are possible, as disclosed below. The circuit breaker chamber 2 has two ends 20 and 21, and includes a first breaker contact 3 that comprises a main contact 30 and an arcing contact 31 , which is in the form of a tulip for example, together with a second breaker contact 4 that comprises a main contact 40 and an arcing contact 41 which in this example is in the form of a rod 42. These two breaker contacts 3 and 4 co-operate with each other between an open end-position (see Fig. 3), in which the two breaker contacts 3 and 4 are completely electrically separated from each other, and a closed end-position (as shown in Fig. 1), in which an electric current can pass between them.

[0028] During the circuit-breaking process, the main contacts or nominal contacts 30 and 40 are separated from each other as shown in Fig. 2, and the arcing contacts 31 and 41 then also separate from each other after a delay period, to form an electric arc that is extinguished by blasting the arc through the nozzle 32. The first breaker contact 3 is fixed relative to the nozzle 32, that is itself an extension of a gas compression space 38. The dielectric nozzle 32 serves as a channel or blowhole or nozzle throat for blasting the insulating gas when passing towards the electrical arc from the compression space 38 during an interrupting action of the circuit breaker 1. The nozzle 32 typically comprises PTFE. In embodiments, the nozzle 32 comprises a metallic ring portion 60 attached at one of its ends. [0029] The two breaker contacts 3 and 4 and the nozzle 32 are displaced along the main axis A- A' of the circuit-breaking chamber 2 of the circuit breaker 1. The breaking chamber 2, nozzle 32, and first and second breaker contacts 3 and 4 are preferably symmetrical about the axis A- A'. Each of the breaker contacts 3 and 4 is actuated, for moving apart or coming together, by means of a single transmission mechanism 5. The transmission mechanism 5 preferably comprises a lever 50 with at least two arms 501 and 502, pivoting about an axis 500 fixed to the chamber 2, one of these arms, 501, being connected to a first connecting rod 51 while the other arm 502 is connected to a second connecting rod 52, the first connecting rod 51 and the second connecting rod 52 being also coupled to the first breaker contact 3 and the second breaker contact 4, respectively. Typically, but not necessarily, the pivot axis 500 for the lever 50 is orthogonal to the displacement axis A- A'. For reasons of symmetry and ease of assembly, the pivot axis 500 for the lever 50 may intersect the displacement axis A- A' (as shown in Fig. 1 to 3), and may in embodiments also be located not to intersect the axis A- A'. The connecting rod 52 is actuated by the movement of breaker contact 3 during a breaking operation via the nozzle 32. To this end, it is mounted to the metallic ring portion 60 of the nozzle 32. The ring portion 60 may comprise aluminium or other lightweight metals. It serves for transmitting the movement of the nozzle 32, as a part of contact 3, during the breaking operation. [0030] The circuit breaker 1 according to embodiments further includes a drive bar 70 coupled to a drive mechanism (not shown), which transmits movement in translation along the axis A- A' to first breaker contact 3. This translatory movement is transmitted via nozzle 32 with metallic ring portion 60 over the transmission mechanism 5 to the second breaker contact 4. [0031] In embodiments of the present disclosure, the first and second breaker contacts 3, 4 are adapted for being electrically connected to the circuit to be switched by circuit breaker 1. The circuit breaker 1 includes an encapsulating case 80 which defines a volume for a gas. Typically, stationary casing 80 is constituted as an insulating envelope, such as, but not limited to, a metallic or ceramic housing. Such insulating envelope is typically mounted on a suitable structure (not shown). [0032] The arcing contacts 31 and 41 are constituted in a manner such that they can conveniently carry an interruption current, so that the arcing contacts do not generate excessive heating and withstand the heat of an arc generated during a current interruption operation of the circuit breaker 1. In particular, arcing contacts 31 and 41 are made of any suitable material, typically arc-resistant material, that enables circuit breaker 1 to function as described herein, such as exemplarily, but not limited to: copper, copper alloys, silver alloys, tungsten, tungsten alloys, or any combination(s) thereof. In particular, these materials are typically chosen on the basis of their electrical conductivity, hardness (i.e. resistance to abrasive wear), mechanical strength, low cost, and/or chemical properties. Typically, the contact rod 42 forming arcing contact 41 is made of any suitable conductive material which enables circuit breaker 1 to function as described herein, such as exemplarily, but not limited to, copper. If required, the contact rod 42 may be made of different materials, for example, different parts thereof may be made of different materials or be coated with a material which provides adequate electrical and/or mechanical properties to each of these parts.

[0033] The exemplary embodiment further includes a gas blast system configured to apply a gas blast on an arc formed between first arcing contact 31 and second arcing contact 41 during a stage of a current interruption operation, in the arcing region located in channel region 33 in the nozzle 32. The gas blast system may include any suitable structure, configuration, arrangement, and/or components that enable to extinguish an electric arc between the arcing contacts. For example, but not limited to, the gas blast system may include appropriate valves, blast pistons, nozzles, arc heaters, and at least one pressure chamber 38 for the self-blast volume and/or for the compression volume. Further elements from known gas blasts systems with which a person of skill in the art will be familiar can be used with at least some of the embodiments described herein without this being described in more detail here.

[0034] In embodiments, the gas blasted by the gas blast system is any suitable gas that enables to adequately extinguish the electric arc formed between the arcing contacts during a current interruption operation, such as, but not limited, to an inert gas as, for example, sulphur hexafluoride SF₆. Thereby, the arc between the first and second arcing contacts 31, 41 develops in an arcing region 33 surrounded by nozzle 32. Thus, the nozzle 32, and particularly its inner face, are subject to stress caused by the heat and electromagnetic emissions of the arcing zone, and to the potentially degrading effects of the hot plasma formed from the insulating gas in the arcing zone. This may include corrosive effects. The circuit breaker in a state where a blasting occurs or is about to occur is shown in Fig. 3. Fig. 2 shows a state shortly before a buildup of an arc during the interrupting operation.

[0035] For the purposes of this disclosure the fluid used in the circuit breaker 1 can be SF₆ gas or any other dielectric insulation medium, may it be gaseous and/or liquid, and in particular can be a dielectric insulation gas or arc quenching gas. Such dielectric insulation medium can for example encompass media comprising an organo fluorine compound, such organo fluorine compound being selected from the group consisting of: a fluoroether, an oxirane, a fluoroamine, a fluoroketone, a fluoroolefin and mixtures and/or decomposition products thereof. Herein, the terms "fluoroether", "oxirane", "fluoroamine", "fluoroketone" and "fluoroolefin" refer to at least partially fluorinated compounds. In particular, the term "fluoroether" encompasses both hydro fluoroethers and perfluoroethers, the term "oxirane" encompasses both hydrofluorooxiranes and perfluorooxiranes, the term "fluoroamine" encompasses both hydrofluoroamines and perfluoroamines, the term "fluoroketone" encompasses both hydrofluoroketones and perfluoroketones, and the term "fluoroolefin" encompasses both hydrofluoroolefms and perfluoroolefins. It can thereby be preferred that the fluoroether, the oxirane, the fluoroamine and the fluoroketone are fully fluorinated, i.e. perfluorinated.

[0036] In embodiments, the dielectric insulation medium is selected from the group consisting of: a hydrofluoroether, a perfluoroketone, a hydrofluoroolefin, and mixtures thereof. [0037] In particular, the term "fluoroketone" as used in the context of the present invention shall be interpreted broadly and shall encompass both fluoromonoketones and fluorodiketones or generally fluoropolyketones. Explicity, more than a single carbonyl group flanked by carbon atoms may be present in the molecule. The term shall also encompass both saturated compounds and unsaturated compounds including double and/or triple bonds between carbon atoms. The at least partially fluorinated alkyl chain of the fluoroketones can be linear or branched and can optionally form a ring. [0038] In embodiments, the dielectric insulation medium comprises at least one compound being a fluoromonoketone and/or comprising also heteroatoms incorporated into the carbon backbone of the molecules, such as at least one of: a nitrogen atom, oxygen atom and sulphur atom, replacing one or more carbon atoms. More preferably, the fluoromonoketone, in particular perfluoroketone, can have from 3 to 15 or from 4 to 12 carbon atoms and particularly from 5 to 9 carbon atoms. Most preferably, it may comprise exactly 5 carbon atoms and/or exactly 6 carbon atoms and/or exactly 7 carbon atoms and/or exactly 8 carbon atoms.

[0039] In embodiments, the dielectric insulation medium comprises at least one compound being a fluoroolefin selected from the group consisting of: hydrofluoroolefins (HFO) comprising at least three carbon atoms, hydro fluoroolefms (HFO) comprising exactly three carbon atoms, trans-l,3,3,3-tetrafluoro-l-propene (HFO-1234ze), 2,3,3,3-tetrafluoro-l-propene (HFO-1234yf), trans- 1,2,3, 3, 3 pentafluoroprop-l-ene (HFO-1225ye (E-isomer)), cis-1,2,3,3,3 pentafluoroprop-l-ene (HFO-1225ye (Z-isomer)), and mixtures thereof.

[0040] The dielectric insulation medium can further comprise a background gas or carrier gas different from the organofluorine compound (in particular different from the fluoroether, the oxirane, the fluoroamine, the fluoroketone and the fluoroolefin) and can in embodiments be selected from the group consisting of: air, N₂, 0₂, CO2, a noble gas, H₂; N0₂, NO, N₂0; fluorocarbons and in particular perfluorocarbons, such as CF₄; CF3I, SF₆; and mixtures thereof.

[0041] The nozzle 32 comprises PTFE, which is relatively stable with respect to adverse effects, such as gas blasting or arcing. The metallic ring portion 60 of the nozzle 32 is at least partially coated with a ceramic material in order to protect it. The ceramic coating 34 is typically thin and thus does not add substantial additional weight, but makes the metallic ring portion 60 more resistant against the hot gases and the arc. In Fig. 1 to Fig. 4, this first ceramic coating 34 on the inner face of the metallic ring portion 60, i.e. on the inner side of the metallic ring portion 60 facing the channel or throat 33 of the nozzle 32, is shown as a thick line. [0042] In embodiments, the same or a similar material can be used to coat 35 the high field stressed area of the metallic ring portion 60, and in particular the at least one metallic shielding element 62 of the metallic ring portion 60, directed or facing towards the other end of the nozzle 32, in order to avoid that metallic particles from the commutation arc can hook up to the metallic ring portion 60, or to the metallic shielding element 62 of the metallic ring portion 60, respectively. This field-protection coating is shown as the second ceramic coating 35 in Fig. 1 to Fig. 4.

[0043] In further embodiments, the end portion of the main contact or nominal contact 40 may also be coated with a third ceramic coating 36, as shown in Figs. 1 to 3. [0044] An additional advantage of the ceramic coating or coatings 34; 35; 36, in particular the first ceramic coating 34 or second ceramic coating 35 or third ceramic coating 36, is the fact, that they prevent the emission of electrons due to high stress by electric fields.

[0045] Fig. 4 shows a detailed view of the nozzle 32 and the metallic ring portion 60 according to embodiments. Therein, a first ceramic coating 34 of the inside of the metallic ring portion 60 is applied, and a second ceramic coating 35 of the rounded protrusion is applied on a face outwards form the channel region 33, i.e. on an outside face of a protrusion of the metallic ring portion 60 which protrusion is arranged radially outside the nozzle 32 and may in addition protrude in an axial direction towards the more distant end of the nozzle 32 thereby forming a metallic shielding element 62. In embodiments, a thread 61 serves for connecting the metallic ring portion 60 to the second connecting rod 52 (see Fig. 1 to 3). As said, the protrusion or metallic shielding element 62 is located in a region radially outwards from the nozzle 32 and axially extending along at least a section of the nozzle 32. The shielding element 62 is coated with the second ceramic coating 35. This second ceramic coating 35 avoids that particles or atoms from the metal of the shielding element 62 are expelled by a high electric field during operation of the circuit breaker 1, which might lead to an unwanted influence on the electric fields in the breaker 1.

[0046] Typical thicknesses of the various ceramic coatings 34; 35; 36, in particular the first ceramic coating 34 or second ceramic coating 35 or third ceramic coating 36, described herein may be from 20 μιη to 200 μιη, more typically from 30 μιη to 100 μιη, e.g. 50 μιη. Each ceramic coating 34; 35; 36 may be applied by all typical techniques known in the art. The inventors have achieved good results with a ceramic coating 34; 35; 36 applied by using a plasma discharge in an electrolytic solution. [0047] Circuit breaker 1 may include, in addition to the elements described above, other further components, such as, but not limited to auxiliary chambers, controllers, cable supports, or any other element which enables the circuit breaker 1 to function as desired in any particular applications.

[0048] Exemplary embodiments of systems and methods for a circuit breaker are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein, and are not limited to practice with only a circuit breaker as described herein. Rather, the exemplary embodiments can be implemented and utilized in connection with many other circuit breaker applications.

[0049] Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. In particular, Fig. 1 illustrates different aspects which may be combined with other general aspects of the present disclosure. Furthermore, method steps can be implemented as device features, and vice versa device features can be implemented as method steps.

[0050] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allows for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A gas-insulated high voltage circuit breaker (1) comprising:

a first arcing contact (31) and a second arcing contact (41), wherein at least one of the two arcing contacts (31, 41) is axially movable along an axis (A-A');

a nozzle (32) surrounding an axially extending channel (33), wherein during a breaking operation an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel (33);

characterized in that the nozzle (32) comprises at least one metallic ring portion (60), which is located at an end of the nozzle (32) and which is coated with a first ceramic coating (34) in order to protect the nozzle (32) from an influence of the arc.

2. The high voltage circuit breaker (1) of claim 1 , wherein the metallic ring portion (60) is part of the nozzle (32), in particular of the inner surface of the nozzle (32); and/or the first ceramic coating (34) is on the inner side of the metallic ring portion (60) facing the throat (33) of the nozzle (32).

3. The high voltage circuit breaker (1) of any one of the preceding claims, wherein at least a part of an inner surface of the nozzle (32) is coated with the first ceramic coating (34) in order to protect the nozzle (32) from an influence of the arc.

4. The high voltage circuit breaker (1) of claim 3, wherein the inner surface of the nozzle (32) is fully coated with the first ceramic coating (34), and/or the inner surface of the nozzle (32) is facing towards the axially extending channel (33).

5. The high voltage circuit breaker (1) of any one of the claims 1 to 4, wherein the metallic ring portion (60) of the nozzle (32) comprises, in particular consists of, aluminium and/or another lightweight material.

6. A gas-insulated high voltage circuit breaker (1), in particular the high voltage circuit breaker (1) of any one of the preceding claims, comprising:

a first arcing contact (31) and a second arcing contact (41), wherein at least one of the two arcing contacts (31, 41) is axially movable along an axis (A-A'); a nozzle (32) surrounding an axially extending channel (33), wherein during a breaking operation, an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel (33);

characterized in that the high voltage circuit breaker (1) further comprises at least one metallic shielding element (62) located in a region radially outwards from the nozzle (32), wherein the shielding element (62) is coated with a second ceramic coating (35) in order to avoid particles from being expelled from the shielding element (62) by a high electric field during operation of the circuit breaker (1).

7. The high voltage circuit breaker (1) of claim 6, wherein the metallic shielding element (62) is part of the nozzle (32).

8. The high voltage circuit breaker (1) of any one of the claims 1 to 5 and any one of the claims 6 to 7, wherein the metallic shielding element (62) is part of the metallic ring portion (60) or is mounted to the metallic ring portion (60).

9. The high voltage circuit breaker (1) of any one of the preceding claims, wherein the first ceramic coating (34) and/or the second ceramic coating (35) and/or a third ceramic coating (36) has or have a thickness of about 20 μιη to about 200 μιη.

10. The high voltage circuit breaker (1) of any one of the preceding claims, wherein the first ceramic coating (34) and/or the second ceramic coating (35) and/or a third ceramic coating (36) has or have been deposited by a plasma discharge in an electrolytic solution.

11. The high voltage circuit breaker (1) of any one of the preceding claims, wherein the first arcing contact (31) and the second arcing contact (41) are movable about the axis (Α-Α').

12. The high voltage circuit breaker (1) of any one of the preceding claims, comprising first and second breaker contacts (3, 4), wherein the first and second breaker contacts (3, 4) are mechanically coupled by a transmission mechanism (5).

13. The high voltage circuit breaker (1) of claim 12, wherein the transmission mechanism (5) comprises at least one connecting rod (52), and the connecting rod (52) is mounted to the nozzle (32).

14. The high voltage circuit breaker (1) of claim 13, wherein the connecting rod (52) is mounted to the nozzle (32) via the metallic ring portion (60).

15. The high voltage circuit breaker (1) of any one of the preceding claims, wherein a dielectric insulation and arc extinguishing fluid present in the circuit breaker (1) comprises an organo fluorine compound selected from the group consisting of: a fluoro- ether, an oxirane, a fluoroamine, a fluoroketone, a fluoroolefin, and mixtures thereof.

16. A gas insulated high voltage circuit breaker (1), in particular the high voltage circuit breaker (1) of any one of the preceding claims, comprising:

- a first arcing contact (31) and a second arcing contact (41), wherein at least one of the two arcing contacts (31, 41) is axially movable along an axis (A-A');

a first nominal contact (30) and a second nominal contact (40), wherein at least one of the two nominal contacts (30, 40) is axially movable along an axis (A-A');

[0020]

- a nozzle (32) surrounding an axially extending channel (33), wherein during a breaking operation, an arc between the first arcing contact and the second arcing contact is formed in an arcing region in the channel (33);

characterized in that an end portion of at least one of the nominal contacts (30, 40) is coated with a third ceramic coating (36).

17. A gas insulated switchgear system, comprising a high voltage circuit breaker (1) according to any one of the preceding claims.