High-speed earthing switch for interrupting non-short circuit currents

Abstract

The present invention relates to a high-speed earthing switch (1), comprising two contacts (2), at least one of which is movable relative to the other between a closed position in which the contact (2) is connected and an open position in which the contact (2) is not connected, the contact (2) defining an arc discharge region in which an arc occurs during a current interruption operation and in which an arc-extinguishing medium is present, and a cylindrical guide tube (3) in which the at least one movable contact (2) forming a piston (4) is slidably arranged for linear movement between a closed position and an open position, the guide tube (3) being closed at an upper end (5) and / or at an opposite lower end (6), thereby defining a first compression chamber (9) with an upper end (5) and / or a second compression chamber (10) with a lower end (6), thereby slowing down the movement of the piston (4) when moving to the open and / or closed positions.

Description

[Technical field]

[0001] The present invention relates to a high-speed earthing switch for interrupting a non-short circuit current, comprising two contacts, at least one of which is movable relative to the other between a closed position in which the contact is connected and an open position in which the contact is not connected, the contacts defining an arc discharge region in which an arc occurs during a current interruption operation and in which an arc-extinguishing medium comprising an arc-extinguishing gas is present, and a cylindrical guide tube in which the at least one movable contact forming a piston is slidably arranged for linear movement between the closed and open positions. [Background technology]

[0002] Dielectric insulating media in liquid or gaseous state are conventionally applied for the insulation of conductive parts in a wide variety of devices, in particular also in GIS or its components. For example, in medium or high voltage metal-enclosed switchgear, the conductive parts are arranged in a gas-tight housing defining an insulating space, said insulating space containing an insulating gas, separating the housing from the conductive parts such that no electric current can pass through the insulating space.

[0003] For current interruption, for example in high-voltage switchgear, the insulating medium further serves as an arc-extinguishing or arc-quenching medium. This is also the case, for example, in disconnecting or earthing switches, where the arc generated during current interruption is extinguished under free-burning conditions, which means that the arc-extinguishing medium is not actively blown towards the arc.

[0004] In conventional gas-insulated switchgear, sulfur hexafluoride (SF6) is typically used as the insulating medium and / or the arc-quenching medium, respectively. Recently, it has been proposed to use organofluorine compounds in the insulating medium, e.g., as an alternative to conventional insulating media, e.g., fluoroketones, which have high insulating capacity, especially high dielectric strength, and high arc-quenching capacity. At the same time, they have a very low Global Warming Potential (GWP) and very low toxicity.

[0005] Fast acting earthing switches are typically operated by an operating mechanism that provides acceleration of the moving contact and also its deceleration. SF6-free solutions for such fast acting earthing switches require an arc blowing mechanism. In principle it is possible to determine the required mass flow rate leading to some kind of pumping mechanism. The piston required to generate the mass flow to the arc requires a mass moving in a linear manner and therefore adds kinetic energy, which requires high performance damping devices with powerful kinetic chains, increasing the cost and technical risk of mechanical life. Summary of the Invention [Problem to be solved by the invention]

[0006] Summary of the Invention SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide an improved speed reduction mechanism for a high speed earthing switch for interrupting non-short circuit currents. [Means for solving the problem]

[0007] The object of the invention is solved by the features of the independent claims. Preferred embodiments are detailed in the dependent claims.

[0008] The object is therefore to provide a high-speed earthing switch, in particular for interrupting non-short circuit currents and / or for directing short circuit currents to earth, comprising: two contacts, at least one of which is movable relative to the other between a closed position in which the contacts are connected and an open position in which the contacts are not connected, the contacts defining an arc discharge region in which an arc occurs during a current interruption operation and in which an arc-extinguishing medium is present; a cylindrical guide tube in which at least one movable contact forming a piston is slidably disposed for linear movement between a closed position and an open position; wherein the guide tube is closed at an upper end and / or an opposite lower end, thereby defining a first compression chamber having an upper end and / or a second compression chamber having a lower end, thereby slowing down the movement of the piston as it moves to the open and / or closed positions.

[0009] The proposed solution performs the deceleration by gas dampers provided at the upper and / or lower ends of the guide tube by the piston and the guide tube, respectively, which results in a reduction of wear and a reduction of the high mechanical loads of the operating mechanism of the high-speed earthing switch of the prior art, which is usually at its maximum load when the deceleration is performed. In other words, the piston, which is necessary to generate the mass flow to the arc, is used in its end position as a gas damper, thereby allowing deceleration at both ends of the stroke. Furthermore, since the kinetic energy absorbed when closing, i.e. moving to the closed position, is much higher than the kinetic energy when opening, i.e. moving to the open position, the proposed solution allows the definition of specific damping characteristics for each direction of movement. Said damping characteristics can be defined, for example, by dimensioning the piston and / or the guide tube at the end of the guide tube, respectively, or by a gas leakage limiting device, which will be described below. Furthermore, with the proposed solution there is no back bouncing, which is fatal in the case of make proof switches, since the gas damper has a 100% efficiency, especially compared to tailor-made oil and rubber dampers, which have a maximum damping efficiency of 50%.

[0010] A high-speed earthing switch, in particular for interrupting non-short circuit currents, is preferably provided as a device designed to interrupt only non-short circuit currents, in particular as a disconnector, more particularly as a high-voltage disconnector, or as an earthing switch, more particularly as a make-proof earthing switch, or as a medium or high voltage gas-insulated switchgear (GIS) comprising such a device. The term "short circuit current", in contrast to a non-short circuit current, can be understood as a current that is established in the first transient phase, at most about 3 seconds after the moment when a component under high voltage is connected to earth from a grid operating under high voltage. According to this definition, the term "non-short circuit current" preferably relates to a current that does not fall under the above definition of "short circuit current".

[0011] A short circuit is preferably understood as an electric circuit that allows a current to travel along an unintended path, often encountering essentially no or very low electrical impedance. In general, such short circuit currents are preferably interrupted within less than 5 seconds after their occurrence, and more quickly, for example in less than 3 seconds, to prevent damage to the electric network. Thus, currents that flow from an electric network, in particular a high-voltage or medium-voltage network, through an unintended or intended path to earth and last longer than 3 seconds or longer than 5 seconds, can be considered as "non-short circuit currents". This definition of non-short circuit currents is preferably based only on their duration and is independent of their magnitude or the intended or unintended nature of their occurrence. In particular, this definition of non-short circuit currents may include nominal currents and excludes short circuit currents with a duration of less than 5 seconds. For example, such non-short circuit currents can be currents induced between two parallel overhead lines, one line connected to earth on both sides and the other line supplying current to a load. Non-short circuit currents induced in earthed overhead lines can be interrupted by the proposed earthing switch.

[0012] The arc-extinguishing medium may comprise air or at least one air component, in particular oxygen (O2) and nitrogen (N2), carbon dioxide (CO2), and mixtures thereof. The air or air component may act as a carrier gas or background gas present in addition to the organofluorine compounds of the arc-extinguishing medium. It is particularly preferred that the ratio of the amount of carbon dioxide to the amount of oxygen is in the range of 50:50 to 100:1. It is particularly preferred that the ratio of the amount of carbon dioxide to the amount of oxygen is in the range of 80:20 to 95:5, more preferably 85:15 to 92:8, even more preferably 87:13 to less than 90:10, and in particular about 89:11. In this regard, it has been found on the one hand that the presence of oxygen in a molar fraction of at least 5% makes it possible to prevent soot formation even after repeated current interruption events involving relatively high current arc discharges. On the other hand, the presence of oxygen in a molar fraction of up to 20% (i.e. 20% or less), more particularly up to 15% (i.e. 15% or less), reduces the risk of degradation of the material of the device due to oxidation. The organofluorine compound may be selected from the group consisting of fluoroethers (including oxiranes), in particular hydrofluoromonoethers, fluoroketones, in particular perfluoroketones, fluoroolefins, in particular hydrofluoroolefins, fluoronitriles, in particular perfluoronitriles, and mixtures thereof. The proposed earthing switch achieves a safe operation despite the relatively low cooling efficiency of the carrier gas.

[0013] At least one movable contact is preferably axially movable relative to the guide tube. The guide tube is preferably provided as a cylinder, in particular a gas-tight cylinder, which is fluidly connected to the arc discharge area. The upper end may constitute an upper radially extending base area of ​​the cylinder and / or the lower end may constitute a lower radially extending base area of ​​the cylinder. The upper end of the movable contact is preferably provided as a piston, in particular integral with the movable contact. The piston, the movable contact each preferably extend perpendicularly through the lower end, in particular through the centre of the lower end.

[0014] According to a preferred embodiment, at least one pressure relief valve is provided at the upper and / or lower end of the guide tube. The pressure relief valve can be provided as a gas leakage limiting device, thereby allowing the creation of specific damping characteristics. Preferably, the pressure relief valve is provided as a through pin in the guide tube.

[0015] In a further preferred embodiment, the piston is provided as a disk-shaped piston with a piston rod that slides on the inner surface of the guide tube and is arranged perpendicular thereto and extends linearly in the direction of movement within the guide tube. The disk-shaped piston preferably extends radially and / or slides gas-tightly on the inner surface of the guide tube. In the inner view, the piston may have a T-shape. The piston rod preferably extends axially together with the guide tube.

[0016] According to another preferred embodiment, the piston rod is hollow and is provided at its upper end with a damper element facing the hollow piston rod and which becomes surrounded by the hollow piston rod when the piston reaches the open position. The damper element preferably has a cylindrical shape and / or extends from the upper end towards the lower end. The damper element is preferably dimensioned such that its outer diameter is slightly smaller than the inner diameter of the hollow piston rod. The hollow piston rod is preferably fluidly connected to the arc discharge region.

[0017] In a further preferred embodiment, the piston rod is provided as a tube and the damper element comprises a tubular shape with a diameter smaller than that of the piston rod, preferably 0, 5, 1, 2, 3, 5 or 10% smaller. The damper element preferably extends into the guide tube over 5, 10, 15 or 20 cm from the upper end.

[0018] According to another preferred embodiment, the disk-shaped piston comprises at least one piston bar-like element extending linearly from the disk-shaped piston in the direction of movement towards the upper end and / or the lower end comprising respective piston bar-like openings through which the piston bar-like element passes when the piston reaches the open and / or closed position. The piston bar-like element preferably extends axially, preferably over 5, 10, 15 or 20 cm, and / or is provided as a rod. The outer diameter of the piston bar-like element is preferably 0, 5, 1, 2, 3, 5 or 10% smaller than the inner diameter of the piston bar-like opening. A plurality of parallel extending piston bar-like elements can be provided. Such piston bar-like elements allow the damping characteristics to be individually adjusted.

[0019] In a further preferred embodiment, the lower end comprises at least one lower bar-shaped element extending linearly from the lower end towards the upper end, and the disk-shaped piston comprises a respective lower bar-shaped opening through which the lower bar-shaped element passes when the piston reaches the closed position. The lower bar-shaped element preferably extends axially, preferably over 5, 10, 15 or 20 cm, and / or is provided as a rod. The outer diameter of the lower bar-shaped element is preferably 0, 5, 1, 2, 3, 5 or 10% smaller than the inner diameter of the lower bar-shaped opening. A plurality of parallel extending lower bar-shaped elements may be provided. Such lower bar-shaped elements allow the damping characteristics to be individually adjusted.

[0020] According to another preferred embodiment, the lower end is provided in the form of a disk surrounding the piston rod, preferably the lower end is gas-tightly connected to the guide cube and / or the piston rod has an outer diameter that is 1, 2, 5 or 10% smaller than the opening of the lower end surrounding the piston rod.

[0021] In a further preferred embodiment, the earthing switch comprises an operating mechanism for the movable contact. The operating mechanism may comprise an operating spring for actuating a closing movement of the movable contact from the open position to the closed position, and / or at least a drive lever attached to an operating shaft for actuating an opening movement of the movable contact from the closed position to the open position. The drive lever may also partially reload the operating spring during the opening movement. Furthermore, the operating mechanism may further comprise coupling means for operably coupling the drive lever to the movable contact.

[0022] According to another preferred embodiment, the upper end of the guide tube is equipped with a gas refill valve. Such a gas refill valve is advantageous to avoid loss of velocity generation in case of low pressure. The same spring can be used for the opening and closing movements. In such a case, the same amount of energy is available for both movements. The velocity can be controlled by utilizing the gas resistance from the piston. That way, the contact can be a little slower to open than to close, but not much slower.

[0023] The object is further solved by a three-pole high voltage (HV) substation comprising, on each pole, a high speed earthing switch as mentioned above, in particular comprising, on each pole, a motor for actuating the high speed earthing switch of the corresponding pole. In the case of such a three-pole HV substation, said high speed earthing switch may in particular be of three-pole operation, with a single motor and mechanical connections for actuating all high speed earthing switch devices, or of single-pole operation, in particular comprising, on each pole, a motor for actuating the high speed earthing switch device of the corresponding pole.

[0024] This object is further achieved by the use of a high speed earthing switch as described above for interrupting non-short circuit currents and / or for directing short circuit currents to earth.

[0025] The object is to provide a method for decelerating the movement of a piston in a high-speed earthing switch, in particular for interrupting non-short circuit currents and / or for directing short circuit currents to earth, the method comprising the steps of: two contacts, at least one of which is movable relative to the other between a closed position in which the contacts are connected and an open position in which the contacts are not connected, the contacts defining an arc discharge region in which an arc occurs during a current interruption operation and in which an arc-extinguishing medium is present; a cylindrical guide tube in which at least one movable contact forming a piston is slidably disposed for linear movement between a closed position and an open position; wherein the guide tube is closed at an upper end and / or an opposite lower end, whereby the piston defines a first compression chamber having an upper end and / or a second compression chamber having a lower end, and the method comprises: Slowing down the movement of the piston when moving to the open and / or closed positions The problem is further solved by a method comprising:

[0026] The proposed method makes it possible to damp the piston in both the open and closed positions without the need for expensive damping devices as known from the prior art, while at the same time applying individual damping characteristics for both positions, thus resulting in a reduction in the costs of the earthing switch and a reduction in the technical risks to its mechanical life.

[0027] Further embodiments and advantages of the method are directly and clearly derived by a person skilled in the art from the earthing switch as described above.

[0028] This object is further solved by the use of a method for decelerating the movement of a piston in a high speed earthing switch for interrupting a non-short circuit current and / or for directing a short circuit current to earth according to the preceding claims.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. [Brief description of the drawings]

[0030] [Figure 1] 1 shows in cross-section the top of a high speed earthing switch for interrupting non-short circuit currents and / or directing short circuit currents to earth according to a preferred embodiment. [Diagram 2] 2 shows in cross section the top of a high speed earthing switch for interrupting non-short circuit currents and / or for directing short circuit currents to earth according to a further preferred embodiment; [Diagram 3] 1 shows in cross-section the top of a high speed earthing switch for interrupting non-short circuit currents and / or directing short circuit currents to earth according to a further preferred embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Description of the Preferred Embodiments 1 to 3 show in cross-section respectively the upper part of a high-speed earthing switch 1 for interrupting non-short circuit currents and / or for directing short circuit currents to earth according to different preferred embodiments.

[0032] The high-speed earthing switch 1 for interrupting non-short circuit currents comprises two contacts 2, one of which is movable relative to the other contact arranged below the movable contact 2, not shown in the figures. Said movable contact is movable between a closed position, in which the contact 2 is electrically connected, and an open position, shown in all figures, in which the contact 2 is not connected. The movable contact 2 can be provided as a tulip contact and the fixed contact as a plug contact or vice versa. Also, both contacts can be arranged movably relative to each other. The two contacts 2 define an arc discharge area, in which an arc occurs during a current interruption operation and in which an arc-extinguishing medium, which comprises an arc-extinguishing gas, is present, not shown in the figures.

[0033] The earthing switch 1 further comprises an airtight cylindrical guide tube 3, specifically a right circular hollow cylinder. The upper end of the movable contact 2 is formed as a T-shaped piston 4 in the cross-sectional view of the figure, whereby said piston 4 is slidably arranged for linear movement in the vertical direction of the figure between a closed position and an open position in the guide tube 3. The guide tube 3 is closed at its upper end 5 and at its opposite lower end 6.

[0034] Specifically, the upper end 5 is provided in a disk shape as a closed base region, and the lower end 6 is provided in a disk shape surrounding a piston rod 7 of the piston 4. The piston 4 is provided as a disk-shaped piston 8 having a disk-shaped head sliding on the inner surface of the guide tube 3, so that the piston 4 defines a first compression chamber 9 having the upper end 5 and a second compression chamber 10 having the lower end 6. When the piston 4 is moved between the open and closed positions, the arc-extinguishing medium present in the guide tube 3 within each of the first compression chamber 9, the second compression chamber 10 is compressed, thereby causing the deceleration of the piston 4 when moving between the open and closed positions, respectively.

[0035] To adjust the damping characteristics of the first compression chamber 9 and the second compression chamber 10, various possibilities exist, which will be described separately below but which can also be combined. As a first measure, a gas leakage limiting device formed by a pressure relief valve 11 can be provided, which can be arranged to extend axially through the upper end 5 and / or the lower end 6 of the guide tube 3.

[0036] In a further embodiment, the piston rod 7 is provided hollow having a tubular shape so that the arc-extinguishing medium can flow from the arc discharge region into the guide tube 3. In this respect, a damper element 12 in the form of a mass cylinder can be arranged at the upper end 5 so as to extend towards the lower end 6 and aligned with the piston rod 7. The outer diameter of the damper element 12 is 2, 5 or 10% smaller than the inner diameter of the piston rod 7.

[0037] In this way, the piston rod 7 encircles the damper element 12 when it reaches the open position. This means that while the piston 4 moves to the open position, the arc-extinguishing medium is compressed in the first compression chamber 9 and subsequently tries to leak through the full diameter of the hollow piston rod 7. However, once the hollow piston rod 7 encircles the damper element 12, the free diameter of the system rod 7 becomes much smaller for the arc-extinguishing medium to leak out, resulting in greater damping at the end of the movement of the piston 7.

[0038] Similarly, the free diameter of the lower end 6 relative to the outer diameter of the piston rod 7 defines the damping characteristics of the second compression chamber 10 when the piston 4 moves to the closed position.

[0039] 2 shows a further embodiment of the earthing switch 1, in which the disk-shaped piston 8 is provided with two axially extending piston rod bar-like elements 13, each of which is provided as a rod and each of which extends linearly in the direction of movement from the disk-shaped piston 13, one towards the upper end 5 and one in its extension towards the lower end 6. Each of the upper end 5 and the lower end 6 is provided with a respective piston bar-like opening 14, through which the piston bar-like element 13 passes when the piston 4 reaches the open and closed positions, respectively.

[0040] The outer diameter of the piston bar-like element 13 is slightly smaller than the inner diameter of the piston bar-like openings 14. The length of the piston bar-like element 13 is dimensioned such that the piston bar-like element 13 can move freely between the open and closed positions without penetrating the respective piston bar-like openings 14, while at the same time penetrating the respective piston bar-like openings 14 in the vicinity of the piston bar-like openings 14, thereby increasing the damping force near the end of the movement.

[0041] 3 shows a further embodiment of the earthing switch 1, in which the lower end 6 is provided with one lower bar-shaped element 15 on each side of the piston rod 7, which extends axially in a straight line from the lower end 6 towards the upper end 5 as a rod. The disc-shaped piston 8 is provided with a respective lower bar-shaped opening 16 through which the respective lower bar-shaped element 15 passes when the piston 4 reaches the closed position. Again, the outer diameter of the lower bar-shaped element 15 is slightly smaller than the inner diameter of the lower bar-shaped opening 16.

[0042] The earthing switch further comprises an operating mechanism 17 for actuating the movable contact 2, as can be seen in Fig. 1. The operating mechanism 17 may comprise an operating spring for actuating a closing movement of the movable contact 2 from the open position to the closed position, and / or at least a drive lever attached to an operating shaft for actuating an opening movement of the movable contact from the closed position to the open position. The described earthing switch can be used in a three-pole high-voltage substation comprising a high-speed earthing switch at each pole and a motor at each pole for actuating the high-speed earthing switch of the corresponding pole.

[0043] While the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description should be considered as illustrative or exemplary and not restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments 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 interpreted as limiting in scope. [Explanation of symbols]

[0044] Reference List 1 Earthing switch 2 Movable Contact 3 Guide tube 4 Piston 5 Upper end 6 Lower end 7 Piston rod 8 Disc-shaped piston 9 First Compression Chamber 10 Second Compression Chamber 11 Pressure relief valve 12 Damper element 13 Piston bar-like element 14 Piston bar-shaped opening 15 Lower bar element 16 Lower bar-shaped opening 17 Operating mechanism

Claims

1. two contacts (2), at least one of which is movable relative to the other between a closed position in which the contact (2) is connected and an open position in which the contact (2) is not connected, the contact (2) defining an arc discharge region in which an arc occurs during a current interruption operation and an arc extinguishing medium is present; a cylindrical guide tube (3) in which the at least one movable contact (2) forming a piston (4) is slidably arranged for linear movement between the closed position and the open position, said guide tube (3) being closed at an upper end (5) and / or at an opposite lower end (6) whereby said piston (4) defines a first compression chamber (9) with said upper end (5) and / or a second compression chamber (10) with said lower end (6), thereby slowing down the movement of said piston (4) when moving to said open position and / or said closed position; and The high-speed earthing switch (1), wherein the piston (4) is provided as a disk-shaped piston (8) having a piston rod (7) that slides on the inner surface of the guide tube (3) and is arranged perpendicular thereto, and that extends linearly in the direction of movement within the guide tube (3).

2. 10. The high speed earthing switch (1) according to the preceding claim, wherein at least one pressure relief valve (11) is provided at the upper end (5) and / or at the lower end (6) of the guide tube (3).

3. 10. A high speed earthing switch (1) according to any of the preceding claims, wherein the piston rod (7) is hollow and the upper end (5) is provided with a damper element (12) facing the hollow piston rod (7) and which becomes surrounded by the hollow piston rod (7) when the piston (4) reaches the open position.

4. 10. The high speed earthing switch (1) according to the preceding claim, wherein the piston rod (7) is provided as a tube and the damper element (12) comprises a tubular shape having a diameter smaller than that of the piston rod (7).

5. 10. The high speed earthing switch (1) according to any of the preceding claims, wherein the disk-shaped piston (8) comprises at least one piston bar-shaped element (13) extending linearly from the disk-shaped piston (8) in a direction of movement towards the upper end (5) and / or the lower end (6), the upper end (5) and / or the lower end (6) comprising respective piston bar-shaped openings (14) through which the bar-shaped element of the piston (4) passes when the piston (4) reaches the open position and / or the closed position.

6. 10. The high speed earthing switch (1) according to any of the preceding claims, wherein the lower end (6) comprises at least one lower bar-shaped element (15) extending linearly from the lower end (6) towards the upper end (5), and the disk-shaped piston (8) comprises respective lower bar-shaped openings (16) through which the lower bar-shaped elements (15) pass when the piston (4) reaches the closed position.

7. 10. The high speed earthing switch (1) according to any of the preceding claims, wherein said lower end (6) is provided in the form of a disk surrounding said piston rod (7).

8. 10. A high speed earthing switch (1) according to any of the preceding claims, comprising an operating mechanism (17) for the movable contact (2).

9. 10. The high speed earthing switch (1) according to any of the preceding claims, wherein the upper end (5) of the guide tube (3) is provided with a gas refill valve.

10. A three-pole high-voltage substation comprising, at each pole, a high-speed earthing switch (1) according to any of the preceding claims, and in particular, at each pole, a motor for operating the high-speed earthing switch (1) of the corresponding pole.

11. Use of a high speed earthing switch (1) according to any of the preceding claims for interrupting a non-short circuit current and / or for directing a short circuit current to earth.

12. A method for slowing down the movement of a piston (4) in a high speed earthing switch (1), comprising: two contacts (2), at least one of which is movable relative to the other between a closed position in which the contact (2) is connected and an open position in which the contact (2) is not connected, the contact (2) defining an arc discharge region in which an arc occurs during a current interruption operation and an arc extinguishing medium is present; a cylindrical guide tube (3) in which the at least one movable contact (2) forming the piston (4) is slidably arranged to move linearly between the closed position and the open position, said guide tube (3) being closed at an upper end (5) and / or at an opposite lower end (6), whereby said piston (4) defines a first compression chamber (9) with said upper end (5) and / or a second compression chamber (10) with said lower end (6); and the piston (4) is provided as a disk-shaped piston (8) having a piston rod (7) sliding on the inner surface of the guide tube (3) and arranged perpendicular thereto, the piston rod (7) extending linearly in the direction of movement within the guide tube (3), and the method comprises the steps of: slowing down the movement of said piston (4) when moving to said open position and / or said closed position.

13. Use of the method for slowing down the movement of a piston (4) in a high speed earthing switch (1) according to the preceding claims for interrupting non-short circuit currents and / or for directing short circuit currents to earth.

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