Technical Field
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The invention relates to a disconnector switch for a high voltage direct current, HVDC, breaker, comprising a contact device comprising a plurality of fixed contacts arranged in a row defining at least one insulating gap between each two fixed contacts and a plurality of moving contacts arranged in another row and each configured for electrically bridging a respective insulating gap in a closed position, and an actuating device comprising an axially extending drive rod fixing the plurality of moving contacts and configured for axially moving the another row of the plurality of moving contacts between an open position and the closed position.
Background Art
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An Ultra-Fast Disconnector, UFD, is a critical component in hybrid High Voltage Direct Current, HVDC, breakers, playing a key role in enhancing performance and reliability of modern HVDC transmission systems. HVDC breakers are essential for controlling and protecting HVDC grids, which are increasingly important as they allow efficient long-distance power transmission and integration of renewable energy sources.
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In such hybrid HVDC breaker, the Ultra-Fast Disconnector is designed to rapidly isolate a faulty section of a HVDC circuit. When a fault is detected in the HVDC transmission system, the UFD is triggered to disconnect a faulted line almost instantaneously, typically within a few milliseconds. This rapid disconnection is crucial because energy levels in HVDC systems are extremely high, and any delay in isolating a fault can lead to severe damage to equipment and extended downtime for the grid.
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The UFD often works in tandem with other components of the hybrid HVDC breaker, such as power electronic switches and energy absorption systems. Upon fault detection, the UFD operates first, creating an open circuit and interrupting a current flow. This swift action significantly reduces stress on the power electronic components, which then complete a fault-clearing process by safely dissipating remaining energy in the circuit. Coordination between the UFD and the electronic switches is vital. The UFD's ultra-fast operation ensures that the fault is isolated before the current can cause significant damage or propagate through the HVDC transmission system.
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UFD's role is also to provide sufficient insulation to withstand a transient interruption voltage, TIV, approximately 1.5 p.u., while the current commutates to a surge arrester branch of the Hybrid HVDC breaker. Such transition from a closed to an open position to achieve sufficient insulation is performed as mentioned before in a few milliseconds, often in 2 ms, so that components of the Hybrid HVDC breaker are not stressed extensively by the fault current.
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Main components of the UFD are a contact system, an actuating mechanism and an enclosure. The contact system consists of moving and fixed contacts. The fixed contacts are usually mounted on shields to limit capacitive and DC field stresses. To achieve a required insulation gap, a number of moving contacts as well as fixed contacts is often more than one. Depending on a UFD topology the moving contacts perform translational or rotational movement. The actuating mechanisms in intended to enable the rotational or translational motion of the moving contacts.
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The moving contacts are usually connected to the mechanical drive with insulating components. Actuating mechanisms are typically of electromagnetic nature and consist of Thomson coils that provide fast response, long stroke distances, fast actuation speeds, and high driving forces. Number of mechanical drives can also be more than one. The enclosure is on ground potential and encompasses the mechanical drives and contact system. The enclosure usually contains pressurized insulation gas to enhance the insulation performance. Depending on the configuration either bushings or spacers are used for connection to busbars.
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Since reachable contact speed is typically of the order of 8 to 15 m/s on average, contact distances are only 15 to 30 mm within the required time. For this an electric field at said separating contacts has to be minimized for with-standing the applied high transient interruption voltage, TIV. Thus, typically multiple separating gaps are used, typically of the order of 6 to 10. For operation of such six-gap system rods in a centre are moved by independent drives to the left and right. In a closed position current is flowing through fixed contact and moving contacts, which are mounted on centre of insulators, connected to the drives.
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In an open position, with voltage applied to one end and ground potential to anther end, a high electric field is developing after current interruption due to the transient interruption voltage, which is defined by the surge arresters of the HVDC circuit breaker. Goal of such design is to have a balanced distribution of electric potential or, with other words, similar electric field stress in the various gaps, which is often not the case.
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Practically, an outer gap typically has highest field stress, whereas other gaps have lower field stress, i.e. the stress is often enhanced in one gap compared to other gaps, which reduces a voltage withstand of the system. Such phenomenon is well known from circuit breakers with multiple interrupter chambers. These circuit breakers use grading capacitors for the purpose of sufficiently uniform electric potential distribution. This solution is, however, expensive and adds additional solid and/or liquid insulation elements which affect the reliability.
Summary of invention
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It is therefore an object of the invention to provide a disconnector switch, in particular an Ultra-Fast Disconnector, UFD, switch for a Hybrid HVDC breaker which has a most uniform respectively balanced distribution of electric potential or, with other words, most similar electric field stress in various gaps, without use of additional elements such as grading capacitors.
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The object of the invention is solved by the features of the independent claim. Preferred implementations are detailed in the dependent claims.
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Thus, the object is solved by a disconnector switch for a high voltage direct current, HVDC, breaker, comprising
- a contact device comprising a plurality of fixed contacts arranged in a row defining at least one insulating gap between each two fixed contacts and a plurality of moving contacts arranged in another row and each configured for electrically bridging a respective insulating gap in a closed position,
- an actuating device comprising an axially extending drive rod fixing the plurality of moving contacts and configured for axially moving the another row of the plurality of moving contacts between an open position and the closed position, and
- an enclosure comprising the contact device and the actuating device arranged therein and filled with a pressurized insulating gas, whereby
- a radially extending width of at least one of the plurality of fixed contacts is at least eight times greater than an axial gap extension of the least one insulating gap.
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A key point of the proposed solution is that a ratio between the radially extending width of the of at least one of the plurality of fixed contacts in respect to the axial gap extension of the least one insulating gap is at least eight times i.e. ≥ 8, thereby resulting in a more respectively uniform electric field distribution between the fixed contacts. By increasing the radially extending width an electric field in a first insulating gap can be decreased and in a neighbouring second insulating can be increased. Such wise a more uniform field distribution is achieved, while in turn voltage withstand of the contact device respectively of the switch is improved.
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The disconnector switch is preferably provided as an Ultra-Fast Disconnector, UFD, switch of a hybrid HVDC breaker and is composed of the contact device, at least one actuating device and the enclosure, for such wise performing rapid and reliable fault isolation. The contact device is intended for making and breaking an electrical connection in a respective circuit where the UFD is installed. In the context of a hybrid HVDC breaker, the contact device is preferably designed for handling very high currents and voltages, for example in a range of hundreds of kilovolts and several kiloamperes, respectively. The moving contacts and/or fixed contacts are preferably made from highly conductive and durable materials, capable of withstanding an intense electrical and thermal stress that may occur during operation of the switch. When the switch is activated, the contact device quickly moves being driven by the actuating device to separate the contacts, creating an open circuit and interrupting current flow. Said separation preferably happens extremely rapidly, usually within a few milliseconds, to prevent a fault current from causing significant damage to the breaker.
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The actuating device drives the moving contacts of the contact device. The actuating device may include electromagnetic actuators or high-speed mechanical drives, for moving the moving contacts. The enclosure houses the contact device and the actuating device for protecting from environmental factors such as dust, moisture, and temperature extremes that could affect performance of said components. In high-voltage applications, the enclosure is typically made from metal or materials that provide excellent electrical insulation and mechanical strength, such as composite insulators or specialized polymers. The enclosure is preferably also intended to contain and control any arcing that might occur when the contacts open, ensuring that the arc is safely extinguished and does not cause damage to surrounding equipment or create a safety hazard. Additionally, the enclosure may be designed to facilitate heat dissipation, as rapid switching of high currents can generate significant amounts of heat.
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The fixed contacts and/or the moving contacts preferably comprise, in an axial top view, a ring-like or cylinder like-shape and/or arranged in regular axial distances to each other. The row and the another row preferably extent in axial direction i.e. parallel to the drive rod. Preferably, the row of fixed contacts circumferentially encompasses the moving contacts, whereby the moving contacts circumferentially encompass the drive rod. In other words, each moving contact preferably comprises an opening through which the drive rod extends. The insulating gap preferably extends in axial direction. Generally, the terms axial and radial correspond to the drive rod respectively an axial extension of the drive rod.
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The moving contacts are preferably fixed to the drive rod in an insulating manner such that two axially neighbouring moving contacts are not electrically connected. Similarly, two axially neighbouring fixed contacts are not electrically connected, for example being hold by an axially extending insulating distance piece defining the insulating gap. Thus, by moving a respective moving contact from the open position, where no electrical contact exists between two neighbouring fixed contacts, into the closed position, the respective insulating gap is bridged by the moving contact electrically connecting the two respective neighbouring fixed contacts. In this respect the term bridging the respective insulating gap in the closed position means that electrical contact is established by the respective moving contact between the two respective neighbouring fixed contacts. Preferably, the contact device comprises N+1 fixed contacts and N moving contacts, with N being a natural number, for example 3, 4, 5, 6, 7, 8, 9, 10 or greater.
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The enclosure is preferably closed, made of metal, connected to ground and/or as said the contact device and the actuating device are arranged within the enclosure. Busbars may pass through the enclosure and electrically connect most outward moving contacts. Said busbars may be externally connected to a high-voltage side of the breaker using bushings and/or spacers. The actuating device preferably comprises a motor of the like and/or is configured for damping movement of the drive rod. The pressurized insulating gas can be provided for example as sulphur hexafluoride gas, SF6, gas, or, in view of known environmental drawbacks of SF6, as carbon dioxide, CO2, Nitrogen, N2, mixtures thereof or other gases, such as for example fluorinated admixtures or O2. The term radially extending width should preferably be understood, exemplary of a ring-like fixed contact, not as overall, radially extending diameter of the ring but rather as ring width.
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According to a preferred implementation, the radially extending width of the at least one of the plurality of fixed contacts is at least ten times, preferably twelve, fourteen, twenty or twenty-four times greater than the axial gap extension of the least one insulating gap. The radially extending width can be equal for all fixed contacts or may decrease in direction away from the actuating device. In a similar manner, the axial gap extension may be the same for all insulating gaps or may vary. Also, an axial extension of the fixed contacts and/or the moving contacts may be equal for all fixed contacts and/or the moving contacts, or may vary per respective contact.
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In another preferred implementation, at least two or at least three fixed contacts facing the actuating device comprise the at least eight times greater radially extending width than the axial gap extension of the respective insulating gap. Preferably the at least two or at least three fixed contacts arranged neighbouring to the actuating device comprise said ratio of the radially extending width in respect to the respective insulating gap.
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According to another preferred implementation, the radially extending width of the plurality of fixed contacts decreases in axial direction away from the actuating device. Preferably the radially extending width decreases in a linear manner, for example by 10 or 20 % per fixed contact.
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In a further preferred implementation, at least one of the plurality of fixed contacts comprises a shield extending away from the respective fixed contact and at least in axial direction away from the actuating device. Said shield may comprise, in axial side view, a flat like shape, in axial top view, a cylinder-like shape, and/or in radial side view, together with the fixed contact, a L-shape. The shield thus increases an axial extension of the respective fixed contact in axial direction away from the actuating device. By means of such shield heat transfer can be improved due to increased surface area. The shield preferably extends from a radially outmost edge or border. The fixed contact, in axial side view, may comprise a rectangle-like shape.
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According to another preferred implementation, the shield radially surrounds a neighbouring fixed contact of the plurality of fixed contacts. Preferably the shield radially surrounds a neighbouring fixed contact of the plurality of fixed contacts facing away from the actuating device. Preferably, the shield radially surrounds the neighbouring fixed contact such that the neighbouring fixed contact is at least partially, around half or completely radially surrounded.
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In a further preferred implementation, the shield comprises an axial shield extension greater, preferably at least two or three times greater, than the axial gap extension of the least one insulating gap. In other words, the axial shield extension of the shield is preferably longer than the axial gap extension and more preferably includes at least a part, around half or a complete axial extension of the fixed contact.
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According to another preferred implementation, the disconnector switch comprises at least three fixed contacts with respective shields, whereby a respective axial shield extension of the respective shields, in direction away from the actuating device, comprise a ratio of 1 : 0,5 : 0,25, preferably 1 : 0,75 : 0,5. With such ratio, preferably of the first, second and third shield respectively fixed contacts facing away from the actuating device, a most uniform field distribution can be achieved.
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In a further preferred implementation, the shield extends in an angle of ? 5° and ≤ 30°, preferably ≥ 10° and ≤ 20° relative to the drive rod. Such non-parallel or inclined shield structures are also possible and could further enhance field uniformity, for example being in a radial or axial direction or both. Thus, the shield may extend not necessarily parallel to the drive rod. In this respect and according to another preferred implementation, the disconnector switch comprises a plurality of shields extending non-parallel or inclined to each other.
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In a further preferred implementation, the shield is provided one piece with the respective fixed contact or is provided separate to the respective fixed contact, preferably firmly connected by a connection means with the respective fixed contact. Such connection means can be provided as a screw or the like. Such wise the shield can be disconnected for maintenance or later connected to an already existing fixed contact. The shield can be provided as metal sheet or plate.
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According to another preferred implementation, the shield comprises an outer surface facing the actuating device and an inner surface facing away from the actuating device, and the outer surface and the inner surface extend non-parallel to each other. Such wise the shield, in axial side view, may comprise a triangle like shape with outer surface and inner surface not extending parallel to each other.
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In a further preferred implementation, the disconnector switch comprises two actuating devices preferably arranged opposite to each other, whereby each actuating device is configured for moving a part of the another row of the plurality of moving contacts preferably in opposite direction. The comprises two actuating devices are preferably configured for moving the respective part simultaneously and/or comprise a respective rod connecting the respective part of the another row of the plurality of moving contacts.
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The object is further solved by a high voltage direct current, HVDC, breaker, comprising the disconnector switch as described before. Said switch respectively the actuating device is preferably configured for carrying out a very fast contact movement within 2 ms, thereby reaching a contact speed of 8 to 15 m/s on average contact distances of 15 to 30 mm.
Brief description of drawings
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These and other aspects of the invention will be apparent from and elucidated with reference to the implementations described hereinafter.
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In the drawings:
- Fig. 1 shows in a schematic view an ultra-fast disconnector, UFD, switch of a high voltage direct current, HVDC, breaker according to a preferred implementation,
- Fig. 2 shows in a schematic view the UFD switch according to Fig. 1 in more detailed view with moving contacts and fixed contacts, and
- Fig. 3 shows at the top the moving contacts and fixed contacts of Fig. 2 in more detailed view in a further implementation and at the bottom a respective electric field distribution between the fixed contacts.
Description of implementations
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Fig. 1 shows in a schematic view an ultra-fast disconnector, UFD, switch of a high voltage direct current, HVDC, breaker with its main components contact device 1, two mechanical actuating devices 2 and enclosure 3. The metal enclosure 3 is on ground potential and encompasses the actuating devices 2 and the contact device 1. The enclosure 3 contains pressurized SF6 or other insulation gas to enhance insulation performance of the switch. Depending on a desired configuration either bushings or spacers, not shown in Fig. 1, are used for connection busbars 4. The busbars 4 are connected to the contact device 1 such that the contact device 1 can switch a current path, marked with arrows in Fig. 1, flowing via the busbars 4.
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The contact device 1 consists of a plurality of moving contacts 5, namely six moving contacts 5, and a plurality of fixed contacts 6, namely seven fixed contacts 6, as can be seen from the schematic view of Fig. 2. The plurality of fixed contacts 6 are arranged in an axially extending row and define a respective insulating gap 7 between each two fixed contacts 6. Likewise, the plurality of moving contacts 5 are arranged in another axially extending row, which extends parallel to the row of the plurality of fixed contacts 6. Each moving contact 5 is configured for electrically bridging the respective insulating gap 7 in a closed position. Fig. 2 shows an open position in which the respective moving contact 5 does not bridge the respective insulating gap 7 between two neighbouring fixed contacts 6. Each moving contact 5 and each fixed contact 6 circumferentially extend around the axis and such wise comprise in axial view a ring respectively cylinder-like shape.
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The two actuating devices 2 enable axial, or in different configurations rotational or translational, motion of the plurality of moving contacts 5. The two actuating devices 2 are arranged opposite to each other and each comprise an axially extending insulating drive rod 8, to which each half of the plurality of moving contacts 5 are fixed via not shown insulating components. Such wise each actuating device 2 can axially move a respective half of the another axially extending row of moving contacts 5 between the open position and the closed position. The actuating devices 2 can be of electromagnetic nature and such wise consist of Thomson coils that provide fast response, long stroke distances, fast actuation speeds, and high driving forces. The actuating devices 2 may comprise dampers, not shown.
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Thereby, according to the proposed solution, an outer radially extending width 9 of at least one of the plurality of fixed contacts 6 is at least eight times greater than an axial gap extension 10 of the least one insulating gap 7. Specifically, the radially extending width 9 of the at least one of the plurality of fixed contacts 6 is at least ten times, preferably twelve, fourteen, twenty or twenty-four times greater than the axial gap extension 10 of the least one insulating gap 7. In the implementation shown in Fig. 2, each fixed contact 6 comprises the same outer radially extending width 9, which is at least eight times greater than the axial gap extension 10 of each insulating gap 7.
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As can be seen in Fig. 2, a six-gap contact device 1 is shown in the open position. For operation, as briefly mentioned before, the rods 8 are moved by the actuating devices 2 to the left and right. In the closed position current is flowing through the fixed contacts 6 and the moving contacts 5, which are mounted on insulators and connected via the rods 8 to the actuating devices 2 as drives. In the open position as shown in Fig. 2, with voltage applied to one end and ground potential to another end a high electric field is developing after current interruption due to transient interruption voltage, TIV, which is defined by surge arresters of the HVDC circuit breaker.
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With the proposed ratio of the outer radially extending width 9 being at least eight times greater than the axial gap extension 10 a design is achieved with has a balanced distribution of electric potential or, with other words, similar electric field stress in the various gaps 7. Thus, the proposed ratio for at least the at least two or at least three fixed contacts 6 facing the actuating device 2 provides a more uniform field distribution.
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Said field distribution can be further uniformed by asymmetric radii of the fixed contacts 6 with the outer radially extending width 9 decreasing away from the actuating devices 2. Fig. 3 show a respective side view of a further implementation where the radially extending width 9 of the fixed contacts 6 decreases in a direction away from the actuating devices 2, not shown in Fig. 3.
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As a further measure, the three outer fixed contacts 6 facing the actuating devices 2 comprise a respective shield 11, which is attached to the radially outer end of the respective fixed contact 6 and extends axially away from the respective fixed contact 6 at least in axial direction away from the not shown actuating device 2. The resulting nearly uniform electric field distribution between the fixed contacts 6 is shown in Fig. 3 at the bottom.
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As can be further seen from Fig. 3 at the top, each shield 11 radially surrounds a neighbouring fixed contact 6 of the plurality of fixed contacts 6. Further, each shield 11 comprises an axial shield extension 12 as axial length, which is greater, preferably at least two or three times greater, than the axial gap extension 10 of the least one insulating gap 7.
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A most uniform electric field distribution can be achieved with at least three fixed contacts 6 with respective shields 11, whereby the respective axial shield extension 12 of the respective shields 11, in direction away from the actuating device 2, comprise a ratio of 1 : 0,5 : 0,25, preferably 1 : 0,75 : 0,5.
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In another possible implementation not shown in the Figs. the shield 11 extends in an angle of ≥ 5° and ≤ 30°, preferably ≥ 10° and ≤ 20° relative to the insulating drive rod 8 i.e. not only in axial direction as shown in Fig. 3 at the top. Thereby, the shields 11 may extend non-parallel or inclined to each other. The shields 2 may extend in an increasing angle in direction away from the actuating device 2.
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In a further possible implementation each shield 11 may comprise an outer surface facing the actuating device 2 and an inner surface facing away from the actuating device 2, whereby the outer surface and the inner surface extend non-parallel to each other. Such wise the shield, in axial side view, may comprise a triangle-like shape.
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Further, the shield 11 can be provided one piece with the respective fixed contact 6 or can be provided separate to the respective fixed contact 6. In the latter case the shield 11 can be firmly connected by a connection means, such as for example a screw, with the respective fixed contact 6. Even further, as can be seen from Fig. 3 at the top, a spiral contact 13 can be attached to a radially inner surface of the fixed contact 6 for establishing the electrical connection between the fixed contact 6 and the respective moving contact 5.
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While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed implementations. Other variations to be disclosed implementations can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.
Reference signs list
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- 1
- contact device
- 2
- actuating device
- 3
- enclosure
- 4
- busbar
- 5
- moving contact
- 6
- fixed contact
- 7
- insulating gap
- 8
- rod
- 9
- radially extending width
- 10
- axial gap extension
- 11
- shield
- 12
- axial shield extension
- 13
- spiral contact