Electrical Switching Device

Abstract

An electrical switching device includes a first switching contact piece and a second switching contact piece. The switching contact pieces can be displaced in relation to each other. The first switching contact piece is surrounded by a fluid flow guiding device. An enveloping contour of a flow duct, disposed between the fluid flow guiding device and the first switching contact piece, is greater at its end facing the second switching contact piece than an enveloping contour of the first switching contact piece at its end facing the second switching contact piece.

Claims

1-15. (canceled)

16. An electrical switching device, comprising: a first switching contact piece and a second switching contact piece, said switching contact pieces being movable relative to one another, said first switching contact piece having a lateral surface side and an enveloping contour with an end facing said second switching contact piece; a fluid flow guiding device surrounding said lateral surface side of said first switching contact piece and forming a flow duct delimited between said fluid flow guiding device and said first switching contact piece, said flow duct having an enveloping contour with an end facing said second switching contact piece; and at least said end of said enveloping contour of said flow duct facing said second switching contact piece, being larger than said end of said enveloping contour of said first switching contact piece facing said second switching contact piece.

17. The electrical switching device according to claim 16, wherein said first switching contact piece has an outer lateral surface and an end facing said second switching contact piece, said outer lateral surface of said first switching contact piece at said end facing said second switching contact piece being accessible from a radial direction.

18. The electrical switching device according to claim 16, wherein said first switching contact piece has an end facing said second switching contact piece and protruding beyond said fluid flow guiding device.

19. The electrical switching device according to claim 16, wherein said first switching contact piece is a bolt-shaped switching contact piece.

20. The electrical switching device according to claim 16, wherein said first switching contact piece is bolt-shaped, said second switching contact piece is bushing-shaped, and said fluid flow guiding device guides a fluid flow around said bolt-shaped first switching contact piece to said bushing-shaped second switching contact piece.

21. The electrical switching device according to claim 16, wherein said fluid flow guiding device and said first switching contact piece are movable.

22. The electrical switching device according to claim 16, wherein said fluid flow guiding device is disposed at a fixed angle relative to said first switching contact piece.

23. The electrical switching device according to claim 16, wherein said first switching contact piece is hollow at least in sections.

24. The electrical switching device according to claim 16, wherein a fluid flow is guided both inside and outside said first switching contact piece.

25. The electrical switching device according to claim 16, wherein a fluid flow traverses a wall of said first switching contact piece.

26. The electrical switching device according to claim 16, wherein said flow duct delimited by said first switching contact piece and said fluid flow guiding device has a substantially ring-shaped cross section.

27. The electrical switching device according to claim 16, which further comprises a shielding hood of said second switching contact piece, said shielding hood having an opening being blocked by said fluid flow guiding device in a contact-connected state of said switching contact pieces.

28. The electrical switching device according to claim 16, wherein said first switching contact piece has an erosion-resistant region being free of radial overlapping by said fluid flow guiding device.

29. The electrical switching device according to claim 16, wherein said switching contact pieces have end sides, and said switching contact pieces are displaceable relative to one another with said end sides situated opposite one another.

30. The electrical switching device according to claim 20, wherein said bushing-shaped second switching contact piece has a centering pin in a bushing opening.

Description

[0038] An exemplary embodiment of the invention will be described in more detail in the text which follows and schematically shown in a drawing below. In said drawing

[0039] FIG. 1 shows an electrical switching device in the connected state,

[0040] FIG. 2 shows the electrical switching device known from FIG. 1 at the beginning of a disconnection movement,

[0041] FIG. 3 shows the electrical switching device known from FIGS. 1 and 2 at an elapsed time of a disconnection movement, and

[0042] FIG. 4 shows the electrical switching device known from FIGS. 1 to 3 in the disconnected state.

[0043] FIG. 1 shows a cross section through an electrical switching device. The basic structure of the electrical switching device will be described with reference to FIG. 1 to begin with.

[0044] The electrical switching device shown in FIG. 1 is a so-called grounding switch with the aid of which ground potential can be applied to a busbar section which serves to transmit current. The electrical switching device is embodied as a pressurized fluid-insulated switching device. To this end, the electrical switching device has a housing 1. The housing 1 is designed as a fluid-tight encapsulation, so that an electrically insulating fluid can be enclosed in the interior. The housing 1 prevents the electrically insulating fluid from evaporating. The housing 1 is designed, for example, as a metal housing 1 which carries ground potential, wherein the electrically insulating fluid which is enclosed in the interior of the housing 1 is pressurized. As a result, the electrical insulation resistance of the electrically insulating fluid is additionally improved. The busbar section, which can be connected to ground by means of the electrical switching device, is likewise arranged within the housing 1. However, provision can also be made for the busbar section which can be connected to ground to be arranged outside the housing 1 or in an adjoining housing in a separate fluid chamber, wherein only electrical contact-connection to the electrical switching device is provided.

[0045] The electrical switching device has a first switching contact piece 2 and a second switching contact piece 3. The first switching contact piece 2 is designed as a bolt-like switching contact piece 2. The second switching contact piece 3 is designed as a bushing-like switching contact piece 3. The second switching contact piece 3 is mounted on the housing 1 and is electrically contact-connected to said housing, so that the ground potential of the housing 1 is also transmitted to the second switching contact piece 3. The second switching contact piece 3 has, for the purpose of forming a bushing, a plurality of contact fingers which are arranged in a manner radially distributed around a longitudinal axis 4, so that a bushing opening 5 is delimited. A centering pin 6 is arranged in the center of the bushing opening 5. The centering pin 6 carries the same electrical potential as the contact fingers which delimit the bushing opening 5. In the direction of the longitudinal axis 4, the centering pin 6 projects beyond the contact fingers which delimit the bushing opening 5. The centering pin 6 is equipped with an erosion-resistant tip at its end which protrudes beyond the bushing opening 5. The centering pin 6 is connected at a fixed angle to the housing 1 by means of a base of the second switching contact piece 3 and is electrically contact-connected to said housing.

[0046] The second contact piece 3 is arranged in the shielding shadow of a shielding hood 7. In the present case, the shielding hood 7 is designed substantially in the shape of a spherical cap and is formed from an electrically conductive material. The shielding hood 7 carries the same electrical potential as the housing 1. The shielding hood 7 is mounted on the housing 1 together with the second switching contact piece 3. The shielding hood 7 has an opening 8. Access to the bushing opening 5 of the second switching contact piece 3 is rendered possible via the opening 8.

[0047] The drivable and therefore movable first switching contact piece 2 is arranged opposite the end side of the bushing opening 5. The first switching contact piece 2 is shaped in a substantially hollow-cylindrical manner. A fluid flow guiding device 9 is seated on the outer lateral surface side of the first switching contact piece 2. The fluid flow guiding device 9 is connected at a fixed angle to the first switching contact piece 2. The fluid flow guiding device 9 further has an inner lateral surface which is positioned at a distance from an outer lateral surface of the first switching contact piece 2, so that a flow duct 10 is formed between the outer lateral surface of the first switching contact piece 2 and the inner lateral surface of the fluid flow guiding device 9. In this case, the flow duct 10 has a substantially circular cross section which substantially has a constant cross section over its extent, so that the flow duct 10, which is delimited by the outer lateral surface of the first switching contact piece 2 and the inner lateral surface of the fluid flow guiding device 9, substantially has a hollow-cylindrical structure. The flow duct 10 has a mouth opening 11 at the free end of the first switching contact piece 2 or at that end which faces the second switching contact piece 3. The mouth opening 11 in turn has a ring-like cross section which has a substantially identical cross section to the profile of the flow duct 10. In this case, the fluid flow guiding device 9 of substantially cylindrical configuration is positioned on the first switching contact piece 2 in such a way that the first switching contact piece 2 protrudes beyond the fluid flow guiding device 9 in the direction of the second switching contact piece 3 (by way of its free end). As a result, the free end of the first switching contact piece 2, which free end faces the second switching contact piece 3, is free of radial overlapping by the fluid flow guiding device 9. Accordingly, radial access to the free end, that is to say to that end of the first switching contact piece 2 which faces the second switching contact piece 3, is rendered possible. Accordingly, contact-making points 12 at which the contact fingers of the second switching contact piece 3, which contact fingers delimit the bushing opening 5, come into contact are arranged on the outer lateral surface side of the first switching contact piece 2. In this case, the end side of the first switching contact piece 2 is formed by an erosion-resistant tip which, as an erosion-resistant region of the first switching contact piece 2, is free of radial overlapping by the fluid flow guiding device 9.

[0048] On account of the hollow-cylindrical configuration of the first switching contact piece 2, that end of the first switching contact piece 2 which faces the second switching contact piece 3 on the end side is provided in the center with a recess into which the centering pin 6 protrudes in the connected state. Therefore, the centering pin 6 can stabilize a linear displacement of the first switching contact piece 2 relative to the second switching contact piece 3, in particular when it is moved into the bushing opening 5 of the second switching contact piece 3. The central recess within the first switching contact piece 2 is blocked by a barrier 13 which delimits the insertion depth of the centering pin 6. Communication openings 14 pass through the circumferential region of a wall of the first switching contact piece 2 on that side of the barrier 13 which is averted from the second switching contact piece 3. The communication openings 14 in the wall of the hollow-cylindrical first switching contact piece 2 allow communication between a hollow space in the interior of the first switching contact piece 2 and the flow duct 10. In this case, a piston 15 which can move relative to the first switching contact piece 2 is arranged in the interior of the first switching contact piece 2. For example, the piston 15 can be arranged fixed in position in relation to the housing 1, whereas the first switching contact piece 2 can be arranged such that it can move in relation to the housing 1 and therefore such that it can move in relation to the piston 15. Connection and disconnection of the electrical switching device can be performed by driving the first switching contact piece 2 by means of a drive device. In this case, the piston 15 sits in a dimensionally complementary manner in the recess of the hollow first switching contact piece 2.

[0049] A disconnection process, that is to say breaking of a ground connection to the busbar section, is intended to be described with reference to FIGS. 1, 2, 3 and 4. In this case, FIG. 1 initially illustrates the connected state of the first and the second switching contact piece 2, 3. That is to say, the first switching contact piece 2 is initially DC-connected to the second switching contact piece 3, so that the ground potential of the housing 1 is transmitted by means of the second switching contact piece 3 to the first switching contact piece 2 and from there to the grounded busbar section. In the event of a disconnection process, a movement is exerted on the first switching contact piece 2. This linear movement of the first switching contact piece 2 takes place in such a way that the first switching contact piece 2 is moved away from the second switching contact piece 3. This results in a reduction in the volume of the recess, which volume is present between the piston 15 and the barrier 13, in the interior of the first switching contact piece 2, as a result of which an excess pressure is produced in the interior of the first switching contact piece 2 in the electrically insulating fluid contained in said interior. In a manner driven by the excess pressure, electrically insulating fluid, which was previously arranged in the interior of the first switching contact piece 2, overflows via the communication openings 14 into the flow duct 10. DC-isolation of the first switching contact piece 2 from the contact fingers, which delimit the bushing opening 5, can lead to an arc being produced. This can be caused, for example, by charging phenomena on the first switching contact piece 2 or on the busbar current section. In the present case, the centering pin 6 is dimensioned in such a way that an electrical contact-connection is not produced due to a direct connection between the centering pin 6 and the second switching contact piece 2 and the first switching contact piece 2 is secured in position only in the event of relatively large vibrations or oscillations of said first switching contact piece. Accordingly, an arc initially extends between the erosion-resistant section of the first switching contact piece 2 and one or more contact fingers which delimit the bushing opening. However, provision can also be made for an arc to be struck at the root between the first switching contact piece 2 and the centering pin 6, in particular at the erosion-resistant sections thereof. On account of the contact overlap of the first and the second switching contact piece 2, 3 (see position of the contact-making points 12) on the lateral surface of the first switching contact piece 2, compression of electrically insulating fluid due to the relative movement of the piston 15 and also the first switching contact piece 2 begins as early as before DC isolation. At the start of the compression, the first and the second switching contact piece 2, 3 are still in electrically conductive contact. Only the position of the contact-making points 12 on the first switching contact piece 2 has shifted. As a result, there is already a continuous application of fluid, which flows out of the flow duct 10, at the time at which the first and the second switching contact piece 2, 3 are DC-isolated. DC isolation of the first and the second switching contact piece 2, 3 can result in an arc being produced (cf. FIG. 2). Application of fluid to the isolating gap between the first and the second switching contact piece 2, 3 has already started at this time, and therefore a striking arc is surrounded by a fluid which is already flowing. As the first switching contact piece 2 moves further away from the second switching contact piece 3 (cf. FIG. 3), fluid exits from the mouth opening 11 of the flow duct 10 with increasing dispersal. This occurs, in particular, since the fluid flow is subject to reduced directivity as the distance between the first switching contact piece 2 and the second switching contact piece 3 increases and therefore also as the distance between the mouth opening 11 and the second switching contact piece 3 increases. As the distance between the first and the second switching contact piece 2, 3 increases, the distance which is to be bridged by an arc increases. In addition to this increasing distance, the arc is blown and therefore cooled and erosion products are moved away from the isolating gap. The conditions for burning of the arc become increasingly worse. Furthermore, particularly when used in isolating or grounding switches, there is a reduction in charges, which drive the arc, across the arc. The arc is quenched. When the arc is quenched, the first switching contact piece 2 can be moved further away from the second switching contact piece 3. The arc is quenched when the end positions (cf. FIG. 4) of the first and the second switching contact piece 2, 3 are reached, that is to say the first and the second switching contact piece 2, 3 are at rest.

[0050] In the event of a connection process, the second switching contact piece 3 is moved closer to the first switching contact piece 2. When the connection position of the first and the second switching contact piece 2, 3 is reached (cf. FIG. 1), the recess for receiving a fluid, which recess is located in the interior of the first switching contact piece 2, is filled with a quantity of fluid, so that disconnection can take place once again with application of an electrically insulating fluid to a possibly striking arc.