EP3590120B1

EP3590120B1 - High-voltage circuit breaker with improved robustness

Info

Publication number: EP3590120B1
Application number: EP18707720.1A
Authority: EP
Inventors: Martin Seeger; Johan Karl Filip COSTYSON; Manuel Gotti; Torsten Votteler; Ulrich Straumann
Original assignee: ABB Power Grids Switzerland AG
Current assignee: Hitachi Energy Ltd
Priority date: 2017-03-02
Filing date: 2018-03-02
Publication date: 2021-02-17
Anticipated expiration: 2038-03-02
Also published as: CN110402475A; WO2018158440A1; EP3590120A1; CN110402475B

Description

BACKGROUND OF THE INVENTION

The subject matter described herein relates generally to a gas-insulated high-voltage circuit breaker, and more particularly, to a circuit breaker having an improved robustness against propagation of an electrical breakdown.
The increase in size of electrical power transmission networks experienced over the last decades have 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. The nozzle typically also serves for guiding a gas stream for extinguishing, or blowing off, the arc. Thereby, the gas is typically guided by a dedicated passage in the nozzle, the heating channel, which ends close to the arcing zone. Thus, the gas is guided directly onto the developing arc.
A potential problem in circuit breakers are electrical breakdowns during an interruption operation, which sometimes enter the heating channel. This is an undesirable behaviour.
EP 1 218 906 B1 discloses a high-voltage power switch, wherein the distance between the first arc contact piece and a second zone of the gas flow-off channel is greater than the doubled diameter of the channel over its first zone. US 2015/021297 A1 discloses a circuit breaker with quenching gas, wherein a ratio of the pressurization chamber outflow limiting area to the nozzle outflow limiting area is less than 1.1:1. DE 199 36 987 C1 discloses a high-voltage switch, wherein a radius of curvature of an electrode is specifically less than the radius of curvature of the arc-contact tip lying opposite to it.
In view of the above and for other reasons, there is a need for the present invention.

BRIEF DESCRIPTION OF THE INVENTION

An interrupter unit for a gas blast circuit breaker, having a central axis A, is provided. The interrupter unit comprises a first contact portion having an arcing contact; a second contact portion comprising a cylinder shaft and a pin contact; a nozzle, comprising an insulating material and fixed to the first contact portion, the nozzle having a first section surrounding the arcing contact, an intermediate cylindrical section and a divergent section and wherein a heating channel is provided having a circumferential opening leading into the nozzle, so as to guide a compressed gas into a zone between the arcing contact and the pin contact during an opening operation of the interrupter unit. In the region of the circumferential opening of the heating channel, there is a circumferential edge region between a first side wall of the heating channel, being oriented towards the second contact portion, and a wall of the cylindrical section of the nozzle, and wherein the circumferential edge region comprises at least one edge with an enveloping radius (which may also be called an effective radius) of at most 2 mm.
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

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:

Fig. 1 shows a diagram of the discharge step length of an arc in an interrupter unit, in dependence of a gas pressure and the applied voltage;
Fig. 2 shows a schematic partial cross-sectional view of an interrupter unit for a circuit breaker, according to embodiments;
Fig. 3 shows a detailed partial cross-sectional view of the interrupter unit of Fig. 2, according to embodiments;
Fig. 4 shows a detailed partial cross-sectional view of an interrupter unit as shown in Fig. 2, according to further embodiments;
Fig. 5 shows a detailed partial cross-sectional view of a further interrupter unit as shown in Fig. 2, according to yet further embodiments;
Fig. 6 shows a detailed partial cross-sectional view of a further interrupter unit as shown in Fig. 2, according to further embodiments.

DETAILED DESCRIPTION OF THE INVENTION

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.
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.
As used herein, an electrical contact through which the nominal current passes through the interrupter unit in a circuit breaker, is called a main contact or nominal contact, and the combination of a main contact and an arcing contact is called henceforth "breaker contact" or "moving contact". The circuit breaker comprises two breaker contacts or moving contacts, each comprising a main contact and an arcing contact. Typically, one of the arcing contacts is configured as a hollow type, also called tulip, and the other arcing contact is configured as a pin contact.
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.
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 or mating arcing contact of the circuit breaker during a stage of the current interruption operation. Thereby, during the interruption operation, an arc develops in an arcing zone between the two arcing contacts, basically and substantially along and parallel to the central symmetrical axis of the interrupter unit. The compressed gas is guided into the arcing zone between the two arcing contacts via a heating channel. The heating channel is configured to have an opening which extends basically or at least partially circumferentially around the arcing zone, such that the gas is flowing into the arcing zone coming from a basically or at least partially ring-shaped circumferential opening around the arcing zone. The opening of the heating channel into the arcing zone may also be formed by holes arranged somehow circumferentially around the arcing zone.
During a regular interruption operation, the arc develops in a direction substantially parallel to the longitudinal or central axis of the interrupter unit, and extends substantially between the two arcing contacts. However, in an unwanted status during an interruption operation, the arc, typically starting at the pin contact, may instead propagate into the opening of the heating channel and further into the heating channel. This is not allowed due to requirements for circuit breakers and may lead to unintended behavior or failure.
The inventors have examined the evolution of such an unintended propagation of an arc into the heating channel, which may for example develop from a prestrike or restrike, and have developed a solution to this problem.
Generally, in embodiments, the propagation of the arc into the heating channel may be suppressed or avoided by a certain configuration of the edge region between the inner side wall of the nozzle and a first side wall of the heating channel at the opening of the heating channel. That is, according to embodiments, the edge region has certain properties. In some embodiments, an edge is configured to have a relatively small effective radius or exact radius of less than 2 mm, preferably equal to or smaller than 1.5 mm or 1.0 mm. The radius of the edge may also be constituted, instead of having a basically quarter-circular shape (in a cross-sectional view, thus forming an exact radius), by at least two consecutively arranged plane sections having growing inclination with respect to the longitudinal axis of the interrupter unit (in a cross-sectional view, thus forming an effective radius or enveloping radius).
In some embodiments, the edge region comprises a sequence of steps, together constituting a kind of stairs. In a first example, the steps each comprise step segments with alternatingly substantially parallel and substantially perpendicular orientation with respect to an end portion of a first side wall of the heating channel and/or with respect to the side wall of the cylindrical section of the nozzle. Thereby, parallel and perpendicular may include a relatively wide tolerance range for the angle, which is laid out further below. In a second example, the steps each comprise step segments with alternatingly substantially radial and substantial axial orientation with respect to the central axis A. In embodiments, substantial parallel is parallel or exactly parallel, substantial perpendicular is perpendicular or exactly perpendicular, substantial radial is radial or exactly radial, and/or substantial axial is axial or exactly radial.
Generally, the above described configurations of the edge region according to embodiments have the effect, that an electric discharge coming from the pin contact does not, or only with a very low probability, enter the heating channel thereby changing its main direction of propagation from axially to radially. When a discharge propagates from the pin contact substantially along the inner side wall of the nozzle, it will not follow a radial path along the wall into the heating channel when there is a sufficiently sharp edge - such as an edge having a small effective radius or exact radius according to embodiments. Thus, in an interrupter unit according to embodiments, the discharge typically detaches from the side wall at the edge region and further propagates axially, instead of following the path along the side wall into the opening of the heating channel. This effect is assumed to be correlated with the discharge step size Ls of the discharge. When the effective edge radius is sufficiently small, thus when the edge or the steps is/are sufficiently - expressed simplified - sharp, the discharge can do a kind of jump over the edge/step, which leads to detachment from the wall and can further axially propagate, instead of following the wall around the edge into the radial heating channel. Typical step sizes Ls from calculations are shown in Fig. 1. From this, it can be seen that the minimum step lengths occurs at the lowest applied voltage (200 kV) and the highest pressure of SF₆ (6 bar). The minimum step length was found to be about 2.5 mm for the investigated parameter range. In order to account for a safety margin, in particular in view that the arc may travel or propagate in an oblique angle over the edge region, the edge thus should have a maximum radius of about 2 mm (including plus/minus 10 percent tolerance). Preferably, the effective or exact radius is equal to or less than 1.5 mm or equal to or less than 1.0 mm. Interrupter units according to embodiments may generally be applied at voltages of 70 kV and larger. While the above and other tests were carried out with SF₆, it is assumed from related testing and experience that the observed behavior of the discharge processes will be similar when employing other suitable buffer gases in interrupter units according to embodiments. Hence, embodiments of the invention include interrupter units having different gases than SF₆, as described further below.
Fig. 2 schematically shows an interrupter unit 1 for a gas blast circuit breaker. It has a central axis A. Only a main section of the unit is shown for illustrational purposes, omitting e.g. a drive unit. The interrupter unit comprises a first contact portion 10 with the arcing contact 12, typically, but not necessarily being a tulip type. A second contact portion 20 comprises a cylinder shaft 22 and the pin contact 25, which is shown in a state after an interrupting process. A nozzle 30 comprises an insulating material, e.g. PTFE, and is fixed to the first contact portion 10. The nozzle has a first section 32 surrounding the arcing contact 12, an intermediate cylindrical section 34 and a divergent section 36. In the cylindrical section 34 is provided a heating channel 40, having a circumferential opening 42 leading into the nozzle 30. During an interrupting/opening operation, a compressed gas is guided into an arcing zone 50 between the arcing contact 12 and the pin contact 25 during an opening operation of the interrupter unit 1.
In the region of the circumferential opening 42 of the heating channel 40, there is a circumferential edge region 46 between a first side wall 60 of the heating channel 40, which first side wall 60 is oriented under an angle to the central axis A, and a wall of the intermediate cylindrical section 34 of the nozzle 30. The circumferential edge region 46 may have, according to embodiments, different configurations. They share the feature that at least one edge 47 with an effective or exact radius of at most 2 mm is provided in the edge region 46.
Various options for the configuration of the edge region 46 are provided below, described with respect to Fig. 3 to Fig. 6.
In Fig. 3, the edge region 46 is shown having an edge 47 with an effective radius r. r is in embodiments about 2.0 mm or less, more preferably 1.5 mm or less and most preferably 1.0 mm or less. As is described above, the edge 47 fosters the axial propagation of a discharge during an interrupting action.
In the embodiment shown in Fig. 4, the circumferential edge region 46 comprises three neighbouring faces 61, 62, 63. The neighbouring faces 61, 62, 63 are at least partially circumferential around central axis A of the interrupter unit. The three, or in other options at least two, neighbouring at least partially circumferential faces 61, 62, 63 together are part of the edge region 46 between the first side wall 60 of the heating channel 40 and the wall of the cylindrical section 34 of the nozzle 30. From their combined inclination, an effective radius r results, which is about 2.0 mm or less, more preferably 1.5 mm or less and most preferably 1.0 mm or less.
The effective radius r is herein also called enveloping radius r. Instead of having a basically quarter-circular shape and an exact radius (in a cross-sectional view) such as, e.g., shown in Fig. 3, an enveloping radius r may be present herein in the case of a non-circular shape (in a cross-sectional view) of the edge between the first side wall 60 of the heating channel 40 and the wall of the cylindrical section 34 of the nozzle 30, as shown in Fig. 4. The enveloping radius is defined as a radius which approximates the real shape of the edge region. In Fig. 4, the enveloping radius is shown as arrow r, wherein the tip of the arrow ends at the "edge" between neighbouring face 61 and neighbouring face 62. Hence, the enveloping radius r may be regarded as the smallest radius which may be fitted to an (irregular, i.e. non-circular) edge so that each location on the edge curve (in a cross-sectional view) is enveloped by the curve of the radius r. While this is exemplarily shown in Fig. 4 only, the concept of the enveloping radius is also applicable to other embodiments described herein. In the case of a principally (quarter-)circular shape of the edge, the enveloping radius is identical to the exact radius.
In the embodiment shown in Fig. 5, the edge region 46 comprises a plurality of steps 56. Thereby, each step 56 has an edge 47 which has an effective or exact radius of significantly less than 2.0 mm, in particular the edges 47 having effective radii or exact radii equal to or smaller than 1.5 mm and preferred equal to or smaller than 1.0 mm and most preferred equal to or smaller than 0.5 mm.
Generally, as shown in Fig. 5, the steps 56 each comprise step segments with alternatingly substantially parallel (v) and substantially perpendicular (h) orientation and a respective dimension - whereby the orientation may be given with respect to an end portion of the first side wall 60 of the heating channel 40, or vice versa (i.e. with exchanging perpendicular (v) and parallel (h)) with respect to the side wall of the cylindrical section 34 of the nozzle 30. Thereby, the step segments each have a length of at most 5 mm, more preferably at most 4 mm or at most 3 mm or at most about 2.5 mm, in the substantially parallel with respect to the first side wall (v) (or radial) direction; and at most about 5 mm, more preferably at most about 2.5 mm, in substantially perpendicular with respect to the first side wall (h) (or axial) direction ("about" meaning +/- 10 percent in this disclosure and including disclosure of "exact").
Thereby, substantially radial (v) (or parallel with respect to the first side wall 60) is intended to include a range of the inclination with respect to the central axis A of the interrupter unit from 70° to 110°, even more from 60° to 120°. Substantially axial (h) (or perpendicular with respect to the first side wall 60) comprises, according to embodiments, a range of inclination with respect to the central axis A from -20° to 20°, even more from -30° to 30°. An example for radial (v) segments with an angle different from 90° is shown in Fig. 6, where a kind of saw-tooth profile results, which may be advantageous in view of the additional reduction of surface currents.
Further, the step segments may have different sizes with respect to each other, meaning a difference between axial (h) and radial (v) segments of the same step 56. Further, steps 56 with varying dimensions between each other may be present.
In the embodiments shown in Fig. 5 and Fig. 6, three steps 56 are shown, however the number of steps may be higher, e.g. 4 or 5, or lower, e.g. 2. In embodiments, to achieve the aimed effect, the steps 56 are provided such that the stair formed by the steps has a pitch line with an inclination angle a (see Fig. 5 and Fig. 6) of at least about 30° with respect to the central axis A (horizontal axis in the Fig. 5 and 6). It has been found out experimentally that the arcing detachment is sufficient when the inclination angle a is 30° or larger, more preferably 45° or larger.
In embodiments, the size of the individual steps may vary, such that the steps 56 form a stair which does not have a constant inclination angle a as in Fig. 5 and Fig. 6. Instead, the inclination angle a varies along a path (in the drawing pane, such as in Fig. 5) connecting the edges 47 of the different steps 56. In other words, the inclination angle has a variation depending on the location at which it is determined. In such cases, the maximum inclination angle a, measured along the path between the edge 47 of the first step 56 - by definition close to the nozzle 33 - and the edge 47 of the last step 56 - by definition close to the heating channel 40 - is at least at one location on the path at least about 30°. That is, at other locations along the path, the inclination can be smaller than 30°. In order to determine or measure the inclination angle a for a configuration as described, a graph may be drawn connecting the edges 47 of the steps 56 using a least mean square procedure.
According to embodiments, the present configuration allows the use of an alternative gas to SF₆ (e.g., as described in WO2014154292 A1 ) having a global warming potential lower than the one of SF₆.
The insulation gas may for example comprise at least one background gas component selected from the group consisting of CO₂, O₂, N₂, H, air, N₂O, in a mixture with a hydrocarbon or an organofluorine compound. For example, the dielectric insulating medium may comprise dry air or technical air. The dielectric insulating medium may in particular comprise an organofluorine compound selected from the group consisting of: a fluoroether, an oxirane, a fluoroamine, a fluoroketone, a fluoroolefin, a fluoronitrile, and mixtures and/or decomposition products thereof. In particular, the insulation gas may comprise as a hydrocarbon at least CH₄, a perfluorinated and/or partially hydrogenated organofluorine compound, and mixtures thereof. The organofluorine compound is preferably selected from the group consisting of: a fluorocarbon, a fluoroether, a fluoroamine, a fluoronitrile, and a fluoroketone; and preferably is a fluoroketone and/or a fluoroether, more preferably a perfluoroketone and/or a hydro fluoroether, more preferably a perfluoroketone having from 4 to 12 carbon atoms and even more preferably a perfluoroketone having 4, 5 or 6 carbon atoms. The insulation gas preferably comprises the fluoroketone mixed with air or an air component such as N₂, O₂, and/or CO₂.
In specific cases, the fluoronitrile mentioned above is a perfluoronitrile, in particular a perfluoronitrile containing two carbon atoms, and/or three carbon atoms, and/or four carbon atoms. More particularly, the fluoronitrile can be a perfluoro-alkylnitrile, specifically perfluoroacetonitrile, perfluoropropionitrile (C2F5CN) and/or perfluorobutyronitrile (C3F7CN). Most particularly, the fluoronitrile can be perfluoro-isobutyronitrile (according to formula (CF3)2CFCN) and/or perfluoro-2-methoxy-propanenitrile (according to formula CF3CF(OCF3)CN). Of these, perfluoroiso-butyronitrile is particularly preferred due to its low toxicity.
Exemplary embodiments of systems and methods for an interrupter unit for a high voltage 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.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only.
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. The patentable scope of the invention is defined by the claims.

Claims

An interrupter unit (1) for a gas blast circuit breaker, having a central axis A, comprising:
a first contact portion (10) having an arcing contact (12);

a second contact portion (20) comprising a mating arcing contact (25),

in particular pin contact (25);

a nozzle (30), comprising an insulating material and being fixed to the first contact portion (10), the nozzle (30) having a first section (32) surrounding the arcing contact (12), an intermediate cylindrical section (34) along the central axis A and a divergent section (36), and wherein a heating channel (40) is provided and has an at least partially circumferential opening (42) leading into the nozzle (30), so as to guide a compressed gas into a zone (50) between the arcing contact (12) and the pin contact (25) during an opening operation of the interrupter unit (1); wherein in the region of the at least partially circumferential opening (42) of the heating channel (40), there is an at least partially circumferential edge region (46) between a first side wall (60) of the heating channel (40), which is oriented under an angle to the central axis A, and a wall of the intermediate cylindrical section (34) of the nozzle (30),

characterised in that

the at least partially circumferential edge region (46) comprises at least one edge (47) with an enveloping radius or an exact radius of at most 2 mm, in particular with an enveloping radius or an exact radius equal to or smaller than 1.5 mm and most preferred equal to or smaller than 1.0 mm.
The interrupter unit of claim 1, wherein the circumferential edge region (46) comprises at least two neighbouring at least partially circumferential faces (61, 62, 63), wherein the at least two neighbouring at least partially circumferential faces (61, 62, 63) together are part of the edge (47) between the first side wall (60) of the heating channel (40) and the wall of the cylindrical section (34) of the nozzle (30), and the enveloping radius of the edge (47) is formed between the first side wall (60) of the heating channel (40) and the wall of the cylindrical section (34) of the nozzle (30).
The interrupter unit of claims 1 or 2, wherein the edge region (46) comprises a plurality of steps (56) with each step (56) comprising an edge (47) having the enveloping radius or the exact radius, in particular the edges (47) having enveloping radii or exact radii equal to or smaller than 1.5 mm and preferred equal to or smaller than 1.0 mm and most preferred equal to or smaller than 0.5 mm.
The interrupter unit of claim 3, wherein the steps (56) each comprise step segments with alternatingly substantially parallel (v), in particular parallel (v), and substantially perpendicular (h), in particular perpendicular (h), orientation with respect to an end portion of the first side wall (60) of the heating channel (40), and in particular wherein the step segments each have a length of less than 5 mm, more preferred at most 4 mm or at most 3 mm, in the substantially parallel or exactly parallel (v) direction and in the substantially perpendicular or exactly perpendicular (h) direction with respect to an end portion of the first side wall (60) of the heating channel (40), wherein substantially parallel (v) is defined to include a range of the inclination with respect to the central axis A of the interrupter unit from 60° to 120°, more specifically from 70° to 110°, and substantially perpendicular (h) is defined to include a range of inclination with respect to the central axis A from -30° to 30°, specifically from -20° to 20°.
The interrupter unit of claim 3 or 4, wherein the steps (56) each comprise step segments with alternatingly substantially perpendicular (v) and substantially parallel (h) orientation with respect to the side wall of the cylindrical section (34) of the nozzle (30), and in particular wherein the step segments each have a length of less than 5 mm, more preferred at most 4 mm or at most 3 mm, in the substantially perpendicular (v) direction and in the substantially parallel (h) direction with respect to the side wall of the cylindrical section (34) of the nozzle (30), wherein substantially perpendicular (v) is defined to include a range of the inclination with respect to the central axis A of the interrupter unit from 60° to 120°, more specifically from 70° to 110°, and substantially parallel (h) is defined to include a range of inclination with respect to the central axis A from - 30° to 30°, more specifically from -20° to 20°.
The interrupter unit of any of claims 3 to 5, wherein the steps (56) each comprise step segments with alternatingly substantially radial (v) and substantially axial (h) orientation with respect to the central axis A, in particular wherein the step segments each have a length of less than 5 mm, more preferred at most 4 mm or at most 3 mm, in the substantially radial (v) direction and in the substantially axial (h) direction, and wherein substantially radial (v) is defined to include a range of the inclination with respect to the central axis A of the interrupter unit from 60° to 120°, more specifically from 70° to 110°, and substantially axial (h) is defined to include a range of inclination with respect to the central axis A from -30° to 30°, more specifically from -20° to 20°, in particular 0°.
The interrupter unit of any of claims 3 to 6, wherein radial (v) and axial (h) step segments are present that have different lengths with respect to each other.
The interrupter unit of any of claims 3 to 7, wherein steps (56) are present that have radial (v) and axial (h) step segments with different lengths with respect to other steps.
The interrupter unit of any of claims 3 to 8, wherein the edge region (46) comprises at least three steps (56), and wherein the steps (56) are provided such that the stair formed by the steps (56) has a pitch line with an inclination angle of at least about 30°, more specifically of at least 45°, with respect to the central axis A, or wherein, when the inclination angle of the pitch line of the stair formed by the steps (56) has a variation between the steps (56) due to the arrangement and/or lengths of the individual steps, a maximum inclination angle is at least about 30°, more specifically is at least 45°.
The interrupter unit of any preceding claim, wherein a side wall (60) of the heating channel (40) is substantially radial with respect to the central axis A at the junction with the nozzle (30), and wherein substantially radial is defined to include a range of the inclination with respect to the central axis A of the interrupter unit from 60° to 120°, more specifically from 70° to 110°.
The interrupter unit of any preceding claim, wherein substantially radial is radial or exactly radial, substantially axial is axial or exactly axial, substantially parallel is parallel or exactly parallel, and/or substantially perpendicular is perpendicular or exactly perpendicular.
The interrupter unit of any preceding claim, wherein the interrupter unit has a voltage rating of 70 kV or higher.
A circuit breaker having an interrupter unit (1) of any of the preceding claims.
A GIS system comprising a circuit breaker of claim 13 or an interrupter unit (1) of any one of the claims 1 to 12.
Use of an interrupter unit (1) of any one of the claims 1 to 12 in a circuit breaker.