High-Voltage Switching Device and Switching System Comprising a High-Voltage Switching Device and Method for Manufacturing a High-Voltage Switching Device

Abstract

The invention relates to a high-voltage switching device comprising a vacuum chamber and to a switching system comprising a high-voltage switching device. The invention further relates to a method for manufacturing a high-voltage switching device comprising a vacuum chamber. The high-voltage switching device has a cast housing 1 consisting of a casting resin, which encloses the housing body 3 of the vacuum chamber 2, which has a fixed contact 4A and a movable contact 5A, an intermediate layer 3A being provided between the inner wall of the cast housing 1 and the outer wall of the housing body 3 of the vacuum chamber 2. The high-voltage switching device is distinguished in that this intermediate layer is a casting resin layer 3A, the glass transition temperature of the casting resin layer being between 10 and 40 C. In a construction of this type, no tears in the coating or casing of the housing body of the vacuum chamber and no external flashovers on the housing body have been found in tests.

Claims

1. High-voltage switching device comprising a cast housing (1) consisting of a casting resin, which encloses a vacuum chamber (2), which has a housing body (3) in which a fixed contact (4A) and a movable contact (5A) are arranged, an intermediate layer (3A) being provided between the inner wall of the cast housing (1) and the outer wall of the housing body (3) of the vacuum chamber (2), characterised in that the intermediate layer (3A) is a casting resin layer, the glass transition temperature of the casting resin layer being between 10 and 40 C.

2. High-voltage switching device according to claim 1, characterised in that the glass transition temperature of the casting resin layer (3A) is between 20 and 30 C.

3. High-voltage switching device according to either claim 1 or claim 2, characterised in that the modulus of elasticity of the casting resin layer (3A) is less than 1000 MPa.

4. High-voltage switching device according to any of claims 1 to 3, characterised in that the modulus of elasticity of the casting resin layer (3A) is greater than 100 MPa, preferably greater than 500 MPa.

5. High-voltage switching device according to any of claims 1 to 4, characterised in that the tensile strength of the casting resin layer (3A) is less than 20 MPa.

6. High-voltage switching device according to any of claims 1 to 5, characterised in that the casting resin is an epoxy resin.

7. High-voltage switching device according to any of claims 1 to 6, characterised in that the cast housing (1) encloses a plastics material body (16) in which an actuation unit for the movable contact is arranged, the housing body (3) of the vacuum chamber (2) being arranged in an upper housing half (1A) in the installed position of the switching device and the plastics material body (16) being arranged in a lower housing half (1B) of the cast housing (1), and the plastics material body (16) having, on the upper face, projections or cutting edges (21) which are cut into the casting resin layer (3A) on the lower face of the plastics material body.

8. Switching system comprising a high-voltage switching device according to any of claims 1 to 7.

9. Method for manufacturing a high-voltage switching device according to claim 1, characterised in that the method has the following method steps: machining the surface of the housing body (3) of the vacuum chamber to increase the surface roughness, applying a casting resin layer (3A) to the outer wall of the housing body (3) of the vacuum chamber (2), machining the surface of the casting resin layer (3A) to increase the surface roughness, introducing the vacuum chamber (2) into a casting mould, casting the space between the inner wall of the casting mould and the outer wall of the vacuum chamber (2) with a casting resin having a glass transition temperature of between 10 and 40 C.

10. Method according to claim 9, characterised in that a casting resin layer (3A), having a glass transition temperature between 10 and 40 C., is applied to the outer wall of the housing body (3) of the vacuum chamber (2).

11. Method according to either claim 9 or claim 10, characterised in that a casting resin layer (3A) having a modulus of elasticity less than 1000 MPa is applied to the outer wall of the housing body (3) of the vacuum chamber (2).

12. Method according to any of claims 9 to 11, characterised in that a casting resin layer having a modulus of elasticity greater than 100 MPa, preferably greater than 500 MPa, is applied to the outer wall of the housing body (3) of the vacuum chamber (2).

13. Method according to any of claims 9 to 12, characterised in that a casting resin layer (3A) having a tensile strength less than 20 MPa is applied to the outer wall of the housing body (3) of the vacuum chamber (2).

14. Method according to any of claims 9 to 13, characterised in that a casting resin layer (3A) consisting of epoxy resin is applied to the outer wall of the housing body (3) of the housing chamber (2).

15. Method according to any of claims 9 to 14, characterised in that the casting resin layer (3A) is applied to the housing body (3) of the vacuum chamber (2) by a pressure gelation process.

16. Method according to any of claims 9 to 15, characterised in that the surface of the housing body (3) of the vacuum chamber (2) is machined in such a way that the surface roughness is greater than 20 m, preferably between 20 m and 40 m, and/or the surface of the casting resin layer (3A) is machined in such a way that the surface roughness is greater than 90 m, preferably between 90 m and 120 m.

Description

[0022] Hereinafter, an embodiment of the invention is described in greater detail, referring to the drawings, in which:

[0023] FIG. 1 is a partially sectional perspective drawing of an embodiment of the high-voltage switching device according to the invention,

[0024] FIG. 2 is a partially sectional perspective drawing of the vacuum chamber of the high-voltage switching device according to the invention, and

[0025] FIG. 3 is an exploded drawing of further components of the high-voltage switching device according to the invention.

[0026] FIG. 1 shows the components essential to the invention of the high-voltage switching device, whilst FIG. 2 shows the vacuum chamber of the switching device. The mutually corresponding parts are provided with like reference numerals in the drawings. The vacuum chamber may for example be a vacuum switching chamber for switching load currents or short-circuit currents in a power switch or a vacuum disconnect chamber for a disconnect switch or earthing switch or combined switch. Hereinafter, the invention is described with reference to a power switch.

[0027] The high-voltage switching device has a cast housing 1, which has an upper housing half 1A and a lower housing half 1B in the normal installed position. In the upper housing half 1A, there is a vacuum chamber 2 having a cylindrical housing body 3 which accommodates an upper, fixed switching contact 4A and a lower, movable switching contact 5B. The housing body 3 of the vacuum chamber 2 may consist of a plurality of components made of metal or ceramic materials. By closing or opening the contacts 4A, 5A, the current path can be closed or interrupted, in other words for example a load current can be switched. In the lower housing half 1B, there is a plastics material body 16, in which a chamber 6 is formed in which an actuation unit for the movable switch contact is arranged. The chamber 6 is filled with an insulating liquid. The actuation unit is described in greater detail below.

[0028] The cast housing 1, produced by injection moulding, of the high-voltage switching device may consist of a conventional casting resin. Preferably, the cast housing consists of epoxy resin. The casting resin has a glass transition temperature (Tg) between 80 and 120 C. The maximum tensile stress of the casting resin (tensile strength) is greater than 60 MPa, and the elongation at break of the casting resin (tensile strength) is less than 3%. The modulus of elasticity (elastic modulus) of the casting resin is greater than 8000 MPa. The cast housing is a solid housing body.

[0029] In the space between the outer wall of the vacuum chamber 2 and the inner wall of the solid cast housing 1, there is an intermediate layer 3A consisting of a casting resin which is more flexible than the casting resin of the cast housing 1.

[0030] The flexible casting resin has a glass transition temperature (Tg) between 10 and 40 C. The maximum tensile stress (tensile strength) of the casting resin is less than 20 MPa and the elongation at break (tensile strength) is greater than 9%. The modulus of elasticity (elasticity modulus) of the casting resin is less than 1000 MPa. Preferably, the modulus of elasticity of the casting resin is greater than 100 MPa, particularly preferably greater than 500 MPa, in particular approximately 600 MPa. As a casting resin, the material known by the name Araldite (Huntsman Advanced Materials), in particular Araldite S-HCEP or Araldite CW 1491/HW 1491, has been found to be particularly advantageous.

[0031] For manufacturing the high-voltage switching device, a layer of the aforementioned material is applied to the housing body 3 of the vacuum chamber 2. The casting resin layer 3A can be applied by methods known in the art. FIG. 2 shows the housing body 3 of the vacuum chamber 2 along with the outer casting resin layer 3A, which extends over the cylindrical peripheral surface and over the upper and lower face, in the installed position, of the housing body of the vacuum chamber.

[0032] Hereinafter, the actuation unit for the movable switching contact and further modules and components of the high-voltage switching device are described in detail, referring to FIGS. 1 to 3.

[0033] The switching contact 5A, which is displaceable in the axial direction of the vacuum chamber 2, is a component of a switching contact element 5, which has a shaft 5B which extends out of the vacuum chamber 2 into the chamber 6 filled with insulating liquid. The shaft 5B of the movable switching contact element 5 is sealed off from the housing body 3 of the vacuum chamber 2 in a vacuum-tight manner by a sealing arrangement (not shown). The lower end of the shaft 5B is connected via an insulating body 7 to an actuation member 8, which extends out of the liquid-filled chamber 6. By actuating the actuation member 8, the movable switching contact element 5 can be axially displaced, in such a way that the contacts 4A, 5A are closed or opened.

[0034] The actuation member 8 has an upper, hollow cylindrical sub-piece 8A, which is located in the chamber 6, and a lower, pin-shaped sub-piece 8B, which is guided longitudinally displaceably in the cylinder space of the upper sub-piece and extends out of the chamber 6. In this context, the upper end piece of the lower sub-piece 8B is braced against a compression spring 9 in the cylinder space of the upper sub-piece 8A. When the lower sub-piece 8B is displaced, the upper sub-piece 8A is also displaced, in such a way that the movable switching contact element 5 is axially displaced. The compression spring 9 is for damping the impacts when the actuation member 8 is actuated. The actuation member 8 is driven by a drive unit (not shown), which displaces the lower sub-piece 8B in an axial direction.

[0035] The actuation member 8 is sealed off from the cast housing 1 in a liquid-tight manner by a sealing arrangement 10. The sealing arrangement 10 has a bellows 11, which encloses the upper sub-piece 8A of the actuation member 8, the upper end of the bellows 11 being connected to the upper sub-piece 8A of the actuation member 8 in a liquid-tight manner. The lower end of the bellows 11 is sealed off from the cast housing 1 in a liquid-tight manner. The bellows 11 and the actuation member 8 are connected to earth potential. On the lower face, the housing body 1 has an opening 12, which is sealed in a liquid-tight manner by a cover 13.

[0036] The liquid-filled chamber 6 has an upper and lower chamber half 6A, 6B in the installed position. In the upper chamber half 6A there is a movable conductor part 12, for example a copper strip, which is connected to the shaft 5B of the movable switching contact element 5. The movable conductor part 12 is electrically connected to further conductor parts 13 (only shown in part) which form the current path. The fixed switching contact element 4 is connected to further conductor parts 14 (only shown in part), which are likewise introduced into the cast housing 1 or placed on the cast housing.

[0037] The plastics material body 16 in the lower housing half 1B of the cast housing 1 is composed of a plurality of plastics material elements 16A, 16B, 16C. FIG. 3 is an exploded drawing of the plastics material elements 16A, 16B, 16C. The plastics material body 16 has in the upper chamber half 6A an upper shell-shaped plastics material element 16A and a lower shell-shaped plastics material element 16B, which enclose the movable conductor part 12, and has in the lower chamber half 6B a cylindrical plastics material element 16C, which encloses the bellows 11. The plastics material elements 16A, 16B, 16C are formed in such a way that they can be assembled conveniently. They are tightly plugged together and/or glued or welded together. All of the plastics material elements 16A, 16B, 16C have rounded corners or edges.

[0038] The two plastics material elements 16A, 16B in the upper chamber half 6A consist of an electrically conductive plastics material; for example, conductive carbon may be added to the plastics material. Since these plastics material elements 16A, 16B can take on the same potential as the movable conductor part 12 or other conductor parts in the chamber, the electrical field is more homogeneous externally.

[0039] The plastics material element 16C in the lower chamber half 6B, which does not consist of a conductive plastics material, cannot carry any potential. This plastics material element 6C provides reliable insulation of voltage-carrying parts in the chamber 6 from the actuation member 8 connected to earth potential. To increase the creepage distance, the plastics material element 16C has lamellae 17 on the outer face.

[0040] The cover 13 of the cast housing 1, which seals the liquid-filled chamber 6, is sealed off from the cylindrical plastics material part 16C in a liquid-tight manner using a sealing ring 18 positioned between the cover and the plastics material part.

[0041] Hereinafter, the method according to the invention for manufacturing the high-voltage switching device is described.

[0042] The housing body 1 of the vacuum chamber 2 is provided with the above-described flexible casting resin layer 3A. For this purpose, the surface of the housing body 3 is initially machined so as to achieve optimal adhesion to the housing body 2. The surface is for example blasted with glass beads, in such a way that the surface roughness is greater than 20 m, preferably between 20 m and 40 m, and the surface is degreased.

[0043] Subsequently, the housing body 1 of the vacuum chamber 2 is introduced into a casting mould (not shown), which may consist of two mould halves, and the casting resin is filled into the space between the inner wall of the mould halves and the outer wall of the housing body 3. The housing body 3 may be cased or coated by the known pressure gelation process. The filling pressure should be above 1 bar. Typical values are 3 to 7 bar. In this way, bubble-free casting can be ensured.

[0044] After the casting resin cures and the mould halves are removed, the surface of the casting or coating is machined so as to achieve optimal adhesion to the casting resin of the solid cast housing 1. The surface of the casting resin layer is machined in such a way that the surface roughness is greater than 90 m, preferably between 90 m and 120 m. The surface may be machined for example by corundum blasting.

[0045] For manufacturing the cast housing 1 of the switching device, a casting mould (not shown in the drawings) is used, which is formed in such a way that it corresponds to the shape and dimensions of the cast housing 1 and to the shape and dimensions of the vacuum chamber 2 provided with the casting resin layer 3A and of the other components switching device. The vacuum chamber 2 is inserted into the upper half of the casting mould, a space 19 being left between the inner wall of the casting mould and the outer wall of the vacuum chamber 2. The plastics material body 16 is introduced into the lower half of the casting mould, a space 20 also being left between the wall of the casting mould and the plastics material body 16. Subsequently, the spaces 19, 20 between the casting mould and the vacuum chamber or plastics material body are cast with a casting material having the above-described material properties.

[0046] The upper plastics material element 16A in the upper chamber half 6A has at the upper edge preferably a plurality of annular projections or cutting edges 21, which cut into the coating or casing 3A of the housing body 3 of the vacuum chamber 2 when the components are pressed together, in such a way that the casting compound for the cast housing, which has a relatively high viscosity in the liquid state, cannot penetrate under pressure into a gap between the housing body 3 of the vacuum chamber 2 and the plastics material body 16.

[0047] After the casting compound has cured, the movable conductor part 12, the actuation member 8, the insulation body 7 and the switching arrangement 10, and optionally further components of the switching device are introduced into the cavity enclosed by the plastics material body 16, and the cavity is filled with the insulating liquid. Thereupon, the cavity is sealed in a liquid-tight manner by placing the cover 13 on.