Power switch comprising at least one vacuum chamber

Abstract

A circuit breaker comprises a vacuum chamber containing a fixed contact and a movable contact. A compensating reservoir with a counter-pressure element is provided to ensure good contact.

Description

[0001] The present invention relates to a medium- or high-voltage circuit breaker comprising at least one vacuum chamber having a longitudinal axis, a fixed contact, and a movable contact subjected to the ambient pressure of the vacuum chamber. A drive mechanism is provided for moving the movable contact between an open and a closed position. A pressure differential between the interior of the vacuum chamber and its surroundings affects the dynamics of the switching process, as it influences the acceleration of the movable contact in addition to the driving force of the drive mechanism. This effect is asymmetrical, namely retarding during opening and accelerating during closing, which affects the respective drive force required for opening and closing. During opening, the switching arc should be extinguished successfully and quickly.Insufficient closing force can cause contacts to weld or stick together during short-circuit currents, or to bounce when reaching the end position.

[0002] During operation, the ambient pressure of the vacuum chamber can vary, for example, due to the current operating temperature, the electrical operating current, fluctuating ambient temperatures, and gas loss, such as leakage when using the circuit breaker in systems with containers that are designed and filled with a gas at higher or lower pressure to adapt the electrical dielectric strength at higher or lower operating voltages. The sometimes significant pressure differences at nominal operating current or during gas pressure loss can complicate the design and may result in a failure to ensure safe closure in the event of pressure loss.

[0003] To move the contacts, the drive mechanism usually has a spring storage unit which is tensioned by motor and / or manually to open and close the movable contact.

[0004] WO 2019 / 145110 A1 discloses an electrical switching device comprising a kinematic chain. A movable switching contact is driven by means of the kinematic chain and is surrounded by an encapsulated housing through which the kinematic chain is fluid-tight. JP S6 148730 A discloses a vacuum circuit breaker arranged in a vacuum chamber. The vacuum circuit breaker has a fixed contact and a movable contact inside the vacuum chamber, the movable contact being connected to a drive mechanism.

[0005] The object of the present invention is to create a power switch of the type mentioned above with which a constant dynamic of the switching process can be achieved almost independently of the ambient pressure of the vacuum clamp, both when opening and when closing the movable contact, and thus an efficient and safe opening and closing of the movable contact.

[0006] These problems are solved by the features of claim 1 and in particular by the fact that, in a circuit breaker of the aforementioned type, the movable contact is connected outside the vacuum chamber to at least one counter-pressure element, which is a movable component of a pressure-tight sealed expansion vessel which has an internal pressure and which is in particular fixedly mounted in a fixed position or in a housing.

[0007] In conventional gas-insulated switchgear, the pressure in the gas-insulated compartment, when using an insulating gas (SF6, nitrogen, carbon dioxide, air, or mixtures with fluorinated gases), is on the order of 0.3 bar (up to 3 bar) for medium-voltage systems and from about 3 bar to 10 bar for high-voltage systems. When the movable contact in the vacuum chamber needs to be moved from its closed to the open position, the differential pressure between the vacuum chamber and the surroundings means that the additional force required to open the movable contact can be comparatively small at atmospheric pressure or in some systems with only low insulating gas pressure. However, if an insulating gas with lower dielectric strength is used in the gas-insulated compartment, the pressure in the gas-insulated compartment must be increased.In practice, this leads to pressures in the gas space of, for example, 3 bar, so that when the movable contact is opened, a differential pressure of about 4 bar results, which requires a correspondingly higher opening force.

[0008] To ensure rapid and proper opening of the movable contact, the drive mechanism or spring accumulator could be dimensioned accordingly larger. However, according to the invention, a counter-pressure element is provided not in the area of ​​the drive mechanism, but on the movable contact itself. This counter-pressure element relieves the movable contact in every position from the ambient pressure acting upon it, for example, an internal pressure P in a bulkhead compartment.

[0009] The counter-pressure element can be dimensioned relatively small in terms of its geometric dimensions, so that the size of the circuit breaker does not increase.

[0010] According to the invention, the counter-pressure element is subjected to the ambient pressure of the vacuum chamber, which also acts on the movable contact of the vacuum chamber, but in the opposite direction. This creates a balanced system by which the forces acting on the movable contact and on the counter-pressure element are essentially compensated, since these are oriented in opposite directions.

[0011] The operating principle described above is independent of the magnitude of the internal pressure P inside a bulkhead compartment, so the described circuit breaker can be used for a wide variety of ambient pressures without requiring any adaptation. Changes in ambient pressure, for example due to temperature fluctuations, also play no role.

[0012] Since the counter-pressure element is part of a pressure-tight sealed expansion tank in which an internal pressure p prevails, the internal pressure p of the expansion tank can be chosen to be lower than the ambient pressure, for example, atmospheric pressure or the internal pressure P within a bulkhead space.

[0013] The vacuum chamber with its associated counterpressure element is arranged in a gas-insulated bulkhead compartment whose internal pressure is greater than the atmospheric pressure surrounding the bulkhead compartment. In this case, it is advantageous that the internal pressure in the expansion tank is lower than the internal pressure in the bulkhead compartment, in particular at least by a factor of 100.

[0014] Advantageous embodiments of the invention are described in the description, the drawing and the dependent claims.

[0015] According to a first advantageous embodiment, the counter-pressure element can be a movable part of the expansion tank, for example a movable plate, membrane or annular surface.

[0016] According to a further advantageous embodiment, the counter-pressure element can be part of an expandable bellows or a vacuum bellows, or the compensating reservoir can have an expandable bellows or vacuum bellows. This allows the characteristics of the compensating reservoir to be very well matched to the characteristics of the vacuum chamber.

[0017] The bellows or vacuum bellows can be designed in various ways, for example, as an edge-welded metal bellows. This allows for a long service life with many switching cycles in a compact design. Alternatively, the reservoir could also be formed by other types of metal bellows or by a vacuum bellows made of polymer material. Gas springs and similar devices are also suitable as reservoirs.

[0018] According to a further advantageous embodiment, the surfaces of the counter-pressure element and the movable contact exposed to ambient pressure can be oriented parallel or orthogonally to each other. A parallel arrangement results in a comparatively simple design. For an orthogonal arrangement, deflecting elements, such as a rocker arm, rotary lever, or the like, can be provided in the connection between the movable contact and the counter-pressure element to direct the force acting on the movable contact and the counter-pressure element in an antiparallel direction.

[0019] According to a further advantageous embodiment, the connection between the counter-pressure element and the movable contact can be arranged parallel or coaxially to the longitudinal axis of the vacuum chamber. This allows the counter-pressure element to act directly on the movable contact, resulting in a compact and space-saving arrangement as well as good force compensation.

[0020] According to a further advantageous embodiment, several vacuum chambers can be provided, the movable contacts of which are connected to only a single counter-pressure element. However, it is also possible to assign each movable contact of each vacuum chamber to a separate counter-pressure element. It is also possible to connect the movable contact of a vacuum chamber to multiple counter-pressure elements.

[0021] According to a further advantageous embodiment, a surface of the counter-pressure element subjected to the internal pressure P within the bulkhead can extend parallel to a surface of the movable contact subjected to the internal pressure P in the bulkhead. This allows the surfaces subjected to the internal pressure P in the bulkhead to exert forces in opposite directions on the movable contact, the ratio of these forces being adjustable by the size of these surfaces and by the internal pressure p in the expansion vessel.

[0022] According to a further advantageous embodiment, the internal pressure p in the expansion vessel can be selected to be lower than the internal pressure P in the bulkhead chamber, wherein the internal pressure p in the expansion vessel can at least partially compensate for a closing pressure acting on the movable contact. Good opening behavior has been observed in arrangements where the internal pressure p in the expansion vessel essentially corresponds to the pressure in the vacuum chamber.

[0023] Since the internal pressure P in the bulkhead acts on the movable contact and the counter-pressure element in opposite directions, a balanced system is created in which the opening movement of the movable contact is independent of the level of the internal pressure P in the bulkhead.

[0024] According to a further advantageous embodiment, the expansion tank can be connected to a housing-mounted component. Such a housing-mounted component can, for example, be a mounting bracket that forms a bearing for the expansion tank.

[0025] According to a further advantageous embodiment, the level of the internal pressure p in the compensating reservoir can essentially correspond to the strength of the vacuum in the vacuum chamber. For example, the deviation can be less than 10% and, in particular, less than 5%. This achieves optimal force compensation. Furthermore, the internal pressure p in the compensating reservoir can be at least 100 times lower than the internal pressure P in a bulkhead.

[0026] The present invention is described below by way of example with reference to an advantageous embodiment and the accompanying drawings. These show: Fig. 1 a schematic representation of part of a circuit breaker of a first embodiment with closed contacts; Fig. 2 a schematic representation of part of the circuit breaker of Fig. 1 with open contacts; Fig. 3 a part of a circuit breaker of a further embodiment with open contacts; Fig. 4 a part of a circuit breaker of a further embodiment with open contacts; and Fig. 5 a schematic representation of a top view of a circuit breaker of a further embodiment.

[0027] Fig. 1Figure 1 shows, as a possible embodiment of the invention, a section of a circuit breaker, for example, of medium-voltage technology, which has (for each phase) a gas-insulated compartment 10 in which a vacuum chamber 12 is arranged, which is only partially shown in the figures. The vacuum chamber 12 has an internal pressure V and a longitudinal axis L, along which a movable contact 14 can be positioned against a fixed contact 16 arranged in the vacuum chamber 12. To move the movable contact 14 between the Fig. 2 the disclosure presented and the in Fig. 1 The closed position shown is achieved by a drive mechanism (not shown) with a lever 24. The drive mechanism transmits the opening or closing movement to the lever 24. This allows the movable contact 14 to be positioned along the axis L against the fixed contact 16.

[0028] As the Figs. 1 and 2To illustrate, the movable contact 14 is attached to a shaft 26 which extends coaxially to the longitudinal axis L and which is electrically conductive and rigidly connected below the vacuum chamber 12 to a flexible conductor 30 in order to establish a current-carrying connection.

[0029] As in Figs. 1 and 2 As shown, a pressure spring 42 is located between the lever 24 and the line 30 on the shaft 26, which ensures that the movable contact 14 is in the closed position ( Fig. 1 ) is always pressed against the fixed contact 16 with a predetermined contact force.

[0030] Furthermore, in this embodiment, a compensating reservoir 44 is provided coaxial to the longitudinal axis L, the pressure spring 42 and the vacuum chamber 12, which is attached on its underside to a housing-fixed component in the form of a horizontal retaining bracket 47, which extends perpendicularly to a vertical strut 45 in the bulkhead space 10.

[0031] The expansion vessel 44 can be designed as a vacuum bellows, as in the illustrated embodiment, and has an internal pressure p that corresponds, for example, to the vacuum V in the vacuum chamber 12. In the illustrated embodiment, a movable section of the expansion vessel 44, namely its upper membrane plate 50, is designed as a counter-pressure element, which is subjected to the internal pressure P within the bulkhead 10. As the figures illustrate, the counter-pressure element 50 has an annular surface subjected to the internal pressure P within the bulkhead 10, which runs parallel to an annular surface of the movable contact 14 subjected to the internal pressure P in the bulkhead 10. The connection between the counter-pressure element 50 of the expansion vessel 44 and the movable contact 14 is provided by the shaft 26, which extends coaxially to the longitudinal axis L.

[0032] How a comparison of Fig. 1 and Fig. 2 As shown, a bellows 46 of the expansion tank 44 is slightly pulled apart when the contacts are closed, and the movable contact 14 contracts when it opens. A lower part 48 of the expansion tank 44 is connected to the stationary mounting bracket 47. The counter-pressure element 50, located on the top of the expansion tank 44, is connected to the shaft 26.

[0033] Similarly, a bellows 18 of the vacuum chamber 12 is connected to the vacuum chamber 12 at its lower end, whereas the upper end of the bellows 18 is sealed to the shaft 26. This allows the internal pressure P to act on the annular surface between the shaft 26 and the bellows 18.

[0034] The operation of the circuit breaker described above is as follows: In the off state, i.e., with the contacts separated, the various components of the circuit breaker are located in the Fig. 2position shown. During the transition from the open position to the closed position, which is shown in Fig. 1 As shown, lever 24 is operated by the in Fig. 2 position shown in the Fig. 1 The lever 24 moves to the position shown. During this movement, the expansion tank 44 expands slightly. After the movable contact 14 touches the fixed contact 16, the lever 24 is moved further towards the fixed contact 16, compressing the pressure spring 42 and causing the Fig. 1 The depicted position of the components results.

[0035] If opening is subsequently required, the lever 24 is pivoted in the opposite direction so that the movable contact 14 lifts off the fixed contact 16. Here, the counter-pressure element 50 compensates for the force acting on the movable contact 14 due to the internal pressure P in the bulkhead 10, since the internal pressure P in the bulkhead 10 exerts a force on the counter-pressure element 50 in the opposite direction. This is particularly advantageous when the ambient pressure of the vacuum chamber, for example, the pressure within the gas-insulated bulkhead, is higher than atmospheric pressure.

[0036] It is understood that the circuit breaker described above, with its components, can have a compartment with corresponding components for each phase.

[0037] The following are, with reference to the Figs. 3 to 5Further embodiments of a circuit breaker are described, using identical reference numerals for identical components.

[0038] Fig. 3 shows another embodiment of a circuit breaker, which differs from the one in Figs. 1 and 2 The embodiment shown differs in that, instead of a single reservoir 44, two reservoirs 44a and 44b are provided at the lower end of the shaft 26, arranged parallel to one another. Both reservoirs are attached to the mounting bracket 47 by their respective lower parts 48a and 48b. The two reservoirs 44a and 44b are connected at their upper ends via a common counter-pressure element 50, to the upper side of which the shaft 26 is attached. Each reservoir 44a and 44b has an expandable bellows 46a and 46b.

[0039] At the in Fig. 4In the illustrated embodiment, the pressure-tight sealed expansion tank 44 is not arranged below the vacuum chamber 12 but next to it, such that the counter-pressure element 50 of the expansion tank 44, with its surface exposed to the ambient pressure P of the vacuum chamber 12, is oriented orthogonally to the surface of the movable contact 14 exposed to the ambient pressure P. The lower part 48 of the expansion tank 44 is attached to the vertical strut 45, so that, in the illustrated embodiment, the counter-pressure element 50, with its surface exposed to the ambient pressure P, extends vertically and at right angles to the horizontal. To achieve the desired force compensation, the lower end of the shaft 26 is connected to the counter-pressure element 50 via an L-shaped rotary lever 27 with a horizontal axis of rotation, the rotary lever 27 being connected to the drive mechanism.This causes the expansion tank 44 to compress when the shaft 26 is moved downwards, as this movement is transferred to the counter-pressure element 50 by a clockwise movement of the rotary lever 27.

[0040] Fig. 5 Figure 1 shows a schematic top view of another embodiment of a circuit breaker. In this embodiment, three vacuum chambers 12, 12' and 12" are arranged side by side and each is provided with a bellows 18, 18' and 18" respectively. The Fig. 5The movable contacts of the three vacuum chambers (not shown) are connected via levers 24a, 24b, and 24c to a shaft 29, which is connected to the drive mechanism. In this embodiment, lever 24b is designed as an extended rotary lever, with one end of the rotary lever 24b connected to the movable contact of vacuum chamber 12' and the opposite end of the rotary lever 24b to the counter-pressure element of the compensating reservoir 44. In this embodiment, the movable contacts and the levers 24a, 24b, and 24c move together, and a single compensating reservoir 44 serves to compensate for the ambient pressure acting on the movable contacts of the vacuum chambers 12, 12', and 12".

Claims

1. A circuit breaker comprising at least one vacuum chamber (12, 12', 12") which has a longitudinal axis (L), a fixed and a movable contact (14, 16), said movable contact being acted on by the environmental pressure of the vacuum chamber, and a drive mechanism (24, 24a, 24b, 24c, 27) for moving the movable contact (14) between an open position and a closed position, wherein the movable contact (14) is connected to at least one counter-pressure element (50) outside the vacuum chamber (12, 12', 12"), said counter-pressure element (50) being a movable component of a compensating reservoir (44, 44a, 44b) which is pressure-tight sealed and which has an inner pressure (p), wherein the counter-pressure element (50) is acted on by the environmental pressure of the vacuum chamber (12, 12', 12"), said environmental pressure also acting on the movable contact (14) of the vacuum chamber (12, 12', 12"), but in the opposite direction of action, characterized in that the vacuum chamber (12, 12', 12") and the counter-pressure element (50) are arranged in a gas-insulated compartment (10) whose inner pressure (P) is greater than the atmospheric pressure surrounding the compartment (10), and in that the inner pressure (p) in the compensating reservoir (44, 44a, 44b) is smaller than the inner pressure (P) in the compartment (10).

2. A circuit breaker in accordance with claim 1, characterized in that the counter-pressure element (50) is a movable part region of the compensating reservoir (44, 44a, 44b).

3. A circuit breaker in accordance with one of the preceding claims, characterized in that the compensating reservoir (44, 44a, 44b) has an expandable bellows (46, 46a, 46b).

4. A circuit breaker in accordance with any one of the preceding claims, characterized in that surfaces of the counter-pressure element (50) and of the movable contact (14) that are acted on by the environmental pressure are oriented in parallel with or orthogonally to one another.

5. A circuit breaker in accordance with any one of the preceding claims, characterized in that the connection (26) between the counter-pressure element (50) and the movable contact (14) is arranged in parallel with or coaxially to the longitudinal axis (L).

6. A circuit breaker in accordance with any one of the preceding claims, characterized in that the connection (26) between the counter-pressure element (50) and the movable contact (14) has a rotary lever (24b, 27).

7. A circuit breaker in accordance with any one of the preceding claims, characterized in that a plurality of vacuum chambers (12, 12', 12") are provided whose movable contacts (14) are connected to a single counter-pressure element (50).

8. A circuit breaker in accordance with any one of the preceding claims, characterized in that the movable contact (14) is connected to a plurality of counter-pressure elements (50).

9. A circuit breaker in accordance with any one of the preceding claims, characterized in that a plurality of vacuum chambers (12, 12', 12") are provided whose movable contacts (14) are connected to a plurality of counter-pressure elements (50).

10. A circuit breaker in accordance with claim 1, characterized in that the inner pressure (p) in the compensating reservoir (44, 44a, 44b) is smaller by at least a factor of 100 than the inner pressure (P) in the compartment (10).

11. A circuit breaker in accordance with claim 1, characterized in that the inner pressure (p) in the compensating reservoir (44, 44a, 44b) at least partly compensates a closing pressure (P) acting on the movable contact (14).

12. A circuit breaker in accordance with any one of the preceding claims, characterized in that the inner pressure (p) in the compensating reservoir (44, 44a, 44b) substantially corresponds to the pressure (V) in the vacuum chamber (12, 12', 12").

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