Vacuum switching device for medium- and high-voltage applications

Abstract

The invention relates to a vacuum switching device (20) for medium or high voltages, comprising two contacts (22, 24), at least one contact (22) of which is mechanically movably mounted by means of a drive rod (26) and thus is in electrical contact with said drive rod (26), wherein the vacuum switching device (20) has a vacuum chamber (28) in which the contacts (22, 24) are arranged. The invention is characterised in that the vacuum switching device has a spring contact, which is outside the vacuum chamber (28), and the drive rod (26), when the contacts (22, 24) are closed, is in electrical contact with a power line via the spring contact (32), and in that the spring contact (32), when the contacts (22, 24) are open (34), is electrically insulated from the drive rod (26).

Description

[0001] The invention relates to a vacuum switching device for medium or high voltage applications according to patent claim 1.

[0002] In medium- and high-voltage switchgear, such as those known from JP S48 15151 U, WO 2007 / 051436 A1, WO 2016 / 001328 A1, EP 0 161 349 A2, and US 2010 / 307901 A1, a contact system comprising two opposing contacts is used to close and open the circuit. One of the two contacts is usually a stationary contact and the other is a moving contact. To close the switchgear, the moving contact is moved toward the stationary contact by a drive. This switching process must not be arbitrarily slow, as an arc is created shortly before the contacts meet, the so-called "making." This can lead to melting of the contact surfaces. The contacts then meet mechanically, and the remaining kinetic energy is dissipated primarily through deformation of the contacts and bouncing.After the molten contacts are mechanically closed, they can fuse together because a slight melting of the contact surfaces occurred shortly before contact. When the contacts are reopened, they can then be damaged by a so-called separation shock.

[0003] In the limiting case, the closing movement can be described as a ballistic movement, in which the moving contact is initially strongly accelerated by a strong drive spring and then moves toward the opposite side, primarily due to inertia. In fact, the spring drive exerts a certain driving force F drive on the contact even during the movement. However, the acceleration decreases during the movement and can approach zero.

[0004] There are fundamentally different approaches to the electrical insulation between the open contacts in a contact system, which can be explained by the so-called Paschen's law. Paschen's law states that in a homogeneous field, the breakdown voltage is a function of the product of gas pressure and electrode spacing. This means that the contacts can be well insulated with a gas or gas mixture at high pressure and the smallest possible contact spacing. The second option is a very low gas pressure, a technical vacuum at approximately 10 -6 bar (abs). Accordingly, the switches are referred to as gas switches or vacuum switches.

[0005] Vacuum switches use vacuum tubes with their switching contacts enclosed in a gas chamber surrounding the vacuum tube to provide electrical insulation from the switch housing or the vacuum tube's electrical connections. Vacuum tubes offer the advantage over gas switches of a very high breaking capacity and a comparatively small contact gap. Furthermore, the vacuum encapsulation prevents decomposition and melting products from switching operations from affecting the surrounding insulation. The contacts of the vacuum tube, especially at the moving contact, are usually connected via a flexible current strip.

[0006] One disadvantage of vacuum tubes is that their contact surfaces are parallel to each other. If the moving contact hits the stationary contact too quickly or with too much kinematic energy, the vacuum interrupter can be damaged, as described above. Furthermore, if the impact speed is too high, they can weld after closing. If the closing is too slow, the contact surfaces can be burned.

[0007] Another disadvantage of a vacuum insulation gap is the inevitable occurrence of so-called non-sustained disruptive discharges (NSDD). These discharges have various causes that are difficult to avoid with conventional designs. This is due, among other things, to the mean free path in a vacuum. At a pressure of 10 to -6 bar, there are practically no molecules or particles between the contacts that could slow down the charge attenuation from one contact to the other or even absorb the charge.

[0008] The object of the invention is to prevent or reduce the two disadvantages of the vacuum tube mentioned above, namely the occurrence of NSDD and the possible welding of the switching contacts caused by an arc.

[0009] The solution to the problem lies in a vacuum switching device for medium or high voltage applications with the features of patent claim 1.

[0010] The vacuum switching device according to the invention for medium or high voltage has two contacts, at least one of which is mounted for mechanical movement via a drive rod and is electrically connected to the drive rod. Furthermore, the vacuum switching device has a vacuum chamber in which the contacts are arranged. The vacuum switching device has a spring contact arranged outside the vacuum chamber, and the drive rod is electrically connected to a power line via the spring contact when the contacts are closed. Furthermore, the spring contact is electrically insulated from the drive rod when the contacts are open.

[0011] The described combination of features means, firstly, that the spring contact resting on the actuator rod allows for targeted friction to be set between the spring contact and the actuator rod, creating appropriate resistance when the actuator rod moves, and minimizing bounce between the contacts when they come into contact. Secondly, when the contacts are open, the current path is interrupted twice: once between the two contacts and once again between the spring contact and the actuator rod, since these are electrically insulated from each other in the open state. In this way, the so-called non-sustained disruptive discharges problem can be statistically reduced to almost zero.

[0012] To control and adjust a targeted mechanical resistance between the spring contact and the actuator rod during a closing movement of the contacts, the actuator rod has a modified cross-sectional contour along a switching axis. For example, the resistance to the translational movement of the actuator rod increases when the cross-section increases along the direction of movement, causing the spring contact to compress.

[0013] Along a switching axis, the actuator rod has an electrically insulating and an electrically conductive section. When the contacts are open, the spring contact rests against the electrically insulating section of the actuator rod, and when closed, it rests against the electrically conductive section. This allows the spring contact to move along the actuator rod in a simple sliding motion during a closing operation.

[0014] In an alternative design, the spring contact is arranged in a contact-free manner with respect to the actuator rod when the contacts are open. This means that there is insulation in the form of an insulating gas between the spring contact and the actuator rod, since the spring contact is located outside the vacuum chamber.

[0015] The cross-sectional contour of the actuator rod is reinforced in such a way that when the actuator rod closes along the switching axis, electrical contact is made between the actuator rod and the spring contact. This reinforcement of the cross-sectional contour occurs in a reinforced area of ​​the actuator rod, which serves to compress the spring contact and thus slow down the closing movement via friction. In particular, this is designed so that this reinforcement engages with the spring contact shortly before the two contacts meet. In this case, it is again expedient for the spring contact to undergo elastic deformation during electrical contact, since the elastic deformation can reversibly introduce frictional energy into the movement of the actuator rod, which has a positive effect on the braking movement.

[0016] The cross-section or cross-sectional contour of the actuator rod tapers again along the switching axis on the side facing away from the contact after maximum amplification and maximum deceleration. This means that after maximum amplification and maximum deceleration, the spring contact rests against the actuator rod in such a way that it permanently presses against it, thus exerting a contact force on the closed contacts. This occurs particularly when the spring contact rests against the tapered area of ​​the cross-section or cross-sectional contour of the actuator rod in an elastically deformed state.

[0017] The changing cross-sectional contour of the actuator rod is preferably designed to be rotationally symmetrical, but other non-symmetric cross-sectional changes can also occur, which lead to engagement of the actuator rod with the spring contact.

[0018] In a further embodiment of the invention, it is expedient that an electrically conductive region of the drive rod can be set to a defined potential via a potential control on the drive rod.

[0019] Further embodiments of the invention and further features are explained in more detail with reference to the following description of the figures. These are schematic, purely exemplary examples that do not represent a limitation of the scope of protection.

[0020] Figures 1 to 4 and 8 show embodiments which are not in accordance with the invention.

[0021] Figures 5 to 7 show an embodiment of the invention.

[0022] Showing: Figure 1a vacuum interrupter in the open state of the contacts and an electrical gas insulation between the operating rod and a spring contact, Figure 2the vacuum interrupter according to Figure 1in half-closed state of the contacts and adjacent spring contact, Figure 3the vacuum interrupter according to Figure 1 and 2 in the closed state of the contacts, Figure 4 a section through the changing cross-sectional contour of the drive rod with the respective adjacent cross-sections, Figures 5 to 7 analog representation of the Figures 1 to 3 with a solid insulation between the electrically conductive drive rod and the spring contact in the three different states as in the Figures 1 to 3 , Figure 8 a schematic representation of an alternative representation of the spring contact and the change in the cross-sectional contour of the actuator rod, Figure 9 a vacuum interrupter according to the prior art with corresponding contacting of the actuator rod according to the prior art.

[0023] In Figure 1A vacuum switching device 20 is depicted, which has a vacuum chamber 28 in which two contacts, a moving contact 22 and a fixed contact 24, are arranged. The moving contact 22 is connected to a drive rod 26, via which the contact 22 is also electrically contacted. The drive rod 26 of the moving contact 22 is in turn in mechanical engagement with a drive (not shown here). The vacuum switching device 20 further comprises a housing 60 on which vapor shields 62 are arranged. Furthermore, the vacuum chamber 28 has insulation 64, which is generally represented in the form of rotationally symmetrical ceramic components. Furthermore, a vacuum bellows 66 serves to seal the drive rod 26 from the gas chamber 30 located outside the vacuum chamber 28.The gas chamber 30 is either a sealed chamber containing a specified insulating gas, where the insulating gas can be, for example, pure air or an additional dielectric insulating gas such as a fluoroketone or a fluoronitrile. However, it is also possible for the vacuum chamber 28 of the vacuum switching device 20 to be located in the open air, which is why the external atmosphere in which the vacuum switching device is located can be considered the gas chamber 30.

[0024] In this respect, the described vacuum switching device 20 according to Figure 1 is analogous to an example shown in Figure 9 The vacuum switching device shown is designed according to the state of the art. The vacuum switching device according to Figure 9 has a current band 70 which is directly connected to the drive rod 26 and thus permanently electrically contacts it.

[0025] In contrast to this design according to Figure 9and the state of the art, the electrical contact of the drive rod 26 is provided by a Figure 1 schematically illustrated spring contact 32, which in turn is electrically connected to another electrical conductor, for example the current strip 70 already described and known from the prior art. In Figure 1 An open state 34 of contacts 22 and 24 is shown, wherein in this state, spring contact 32, which is located outside the vacuum chamber 28 in the gas chamber 32, is arranged at a distance from the drive rod 26. The distance of spring contact 32 from the drive rod 26 is so large that no electrical contact occurs in this state 34. An insulating gas, for example, synthetic air, is present between spring contact 32 and the drive rod 26.

[0026] On a side of the spring contact facing away from contacts 22 and 24, there is a change in the cross-sectional contour 38 of the drive rod 26. If, as in Figure 2 When, as shown, a movement occurs along the arrow F a , a mechanical engagement of the spring contact 32 with the drive rod 26 or its increasing cross-sectional contour 38-I occurs. Thus, the spring contact 32 is elastically deformed, which is expressed by the spring force F s . Furthermore, a further force F b occurs, which can be referred to as a braking force and which counteracts a closing movement 46 along a switching axis 36.

[0027] The braking force F b occurring due to the described intervention prevents the moving contact 22 from striking the fixed contact 24 too strongly, which considerably reduces the undesirable bouncing of the two contacts 22 and 24 known from the prior art.

[0028] Furthermore, Figure 3a closed state 44 of the contacts 22 and 24 is shown, wherein the cross-sectional contour 38 extends after a region of maximum amplification 50 ( Figure 4 ) is tapered again in such a way that the spring contact 32 rests against the drive rod 26 in such a way that the contact system with the contacts 22 and 24 is pressed closed, which in turn prevents bouncing in the closed state, since the contact force F b prevents the contacts 22 and 24 from opening again.

[0029] In Figure 4 is an enlarged schematic representation of the drive rod 26 and its cross-sectional contour 38 I to IV, which shows the individual stations from the Figures 1 to 3 explained in more detail. Figure 4 For the sake of clarity, the spring contact in the open state 34 of the contacts 22 and 24 is not shown, as shown in Figure 1is shown, approximately at the height of the cross-sectional contour 38-I. Here, there is also an electrical insulation between the spring contact 32 and the drive rod 26. Furthermore, the drive rod 26 moves along the switching axis 36 in the illustration according to Figure 4upwards, whereby in the cross-sectional contour 38-II the spring contact 32 comes into contact with the actuator rod 26. The actuator rod 26 performs a closing movement in the direction of the arrow 46. In this stage the actuator rod 26 is braked due to the elastic deformation and the pressing of the spring contact 32 in the area 38-II. In the area 38-II there is an area 38-III along the closing movement 46, which represents a maximum cross-sectional contour of the actuator rod 26. This is the area of ​​maximum reinforcement 50. As the closing movement 46 continues, the spring contact 32 slides over the area 50 and comes into an area 52, which in turn has a tapered cross-sectional structure, which is provided with the reference number 38-IV. In this area 52, the spring contact 32 is still elastically deformed and rests against the drive rod 26 and exerts a locking force on the contacts 22 and 24.

[0030] The Figures 1 to 4 The vacuum switching device 20 described has the following advantages over the prior art. Firstly, the current path is interrupted twice, namely once between contacts 22 and 24 and once between the operating rod 26 and the spring contact 32. This statistically almost eliminates the possibility of NSDD. Secondly, the special design of the operating rod and its engagement with the spring contact 32 in the described manner greatly reduces the bouncing of contacts 22 and 24 upon contact, significantly reducing welding and damage to contact surfaces 58 of contacts 22 and 24.

[0031] In the Figures 5 , 6 and 7 an analogous movement of the contacts 22 and 24 to each other is described, as already described for the Figures 1 to 3 was explained in detail. The difference to the Figures 1 to 3 consists in the Figures 5 to 7in that the electrical insulation between the spring contact 32 and the actuator rod 26 in the open state 34 of the contacts 22 and 24 is provided by a solid insulation, for example, polytetrafluoroethylene. The electrically insulating area 40 on the actuator rod 26 is thus surrounded, for example, by a sleeve made of this solid insulation material, and the spring contact 32 rests there in an insulating manner. When the actuator rod 26 moves, the spring contact moves analogously to Figure 2 from the electrically insulated area 40 into an electrically conductive area 42. Thus, the drive rod 26 is contacted with the electrical current path.

[0032] In the Figures 5 to 7 a similar cross-sectional change 38-I to 38-IV is shown, as in the Figures 1 to 3is the case. In principle, this is not absolutely necessary to achieve a braking effect of the drive rod 26 and the contact 24 before they hit the contact 22. Other measures would also serve this purpose, for example, increasing the force F s . at which the spring contact 32 is pressed against the drive rod 26.

[0033] Another alternative design is in Figure 8 shown very schematically, in Figure 8only the contacts 22 and 24 as well as the drive rod 26 and the spring contact 32 of the vacuum switching device 20, which is not shown in its entirety here, are shown. When the closing movement occurs in the direction of arrow 46, the spring contact 32, which is designed in the form of a flat spring, is pressed against a disk mounted on the drive rod 26, whereby this construction also has a change in the cross-sectional contour 38-I to 38-IV. The tapered region 52 and the thickening region 54 can be very short along the switching axis and reduced to zero. It is important that the spring contact 32 is designed in such a way that a targeted braking of the drive rod 26 and the contact 22 can take place.

[0034] It should be noted that in the open state 34 of the contacts, a defined potential, which results from the network environment, should be applied to the drive rod. It should also be noted that the design of the contacts used in the Figures 1 to 9 described are purely exemplary; in principle, pot contacts or pin-tulip contacts can also be used for the described technological implementation.

Claims

1. Vacuum switching device (20) for medium or high voltage, having two contacts (22, 24), of which at least one (22) is mounted so as to be mechanically movable via a drive rod (26) and at the same time is electrically connected to the drive rod (26), wherein the vacuum switching device (20) has a vacuum space (28) in which the contacts (22, 24) are arranged, and wherein the vacuum switching device has a spring contact, which is arranged outside the vacuum space (28), and the drive rod (26), in a closed state of the contacts (22, 24), is electrically connected to a power line via the spring contact (32), and wherein the spring contact (32), in the open state (34) of the contacts (22, 24), is electrically insulated from the drive rod (26), wherein the drive rod has a cross-sectional contour (38-I, 38-II, 38-III, 38-IV) that varies along a switching axis (36), and wherein the cross-sectional contour (38-I to 38-III) of the drive rod (26) is thickened (thickening region 54) in such a way that, during a closing movement (46) of the drive rod (26) along the switching axis (36), electrical contact is made between the drive rod (26) and the spring contact (32), characterized in that the drive rod (26) has, along the switching axis, an electrically insulating region (40) and an electrically conducting region (42) and the spring contact, in an open state (44) of the contacts (22, 24), bears on the electrically insulating region (40) of the drive rod (26), and in that the cross-sectional contour (38-IV) of the drive rod (26) narrows again along the switching axis (36) on a side (48) facing away from the contacts (22, 24) after a maximum thickening (50).

2. Vacuum switching device according to Claim 1, characterized in that the spring contact (32) is subjected to elastic deformation while the electrical contact is being made.

3. Vacuum switching device according to Claim 2, characterized in that, in a closed state (44) of the contacts (22, 24), the spring contact (32) bears in an elastically deformed state against the narrowing region (52) of the cross-sectional contour (38-IV) of the drive rod (26).

4. Vacuum switching device according to either of Claims 2 and 3, characterized in that the varying cross-sectional contour of the drive rod (26) is configured in a rotationally symmetric manner.

5. Vacuum switching device according to one of the preceding claims, characterized in that, in an electrically conducting region (42) of the drive rod (26), a defined potential is settable via a potential controller (56) on the drive rod (26).

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