HIGH-VOLTAGE FEEDBACK AND ELECTRICAL HIGH-VOLTAGE DEVICE WITH HIGH-VOLTAGE FEEDBACK

Description

[0001] The invention relates to a high-voltage bushing comprising an inner conductor extending through an insulating body, a housing at least partially enclosing the insulating body on the outside, and a mounting flange for attaching the high-voltage bushing to a wall of a high-voltage device. Suitably, a first axial end of the inner conductor is provided for connection to an electrical conductor of the high-voltage electrical device, and a second axial end of the inner conductor is provided for connection to another electrical line.

[0002] A high-voltage bushing of this type is known from WO 2019 / 011426 A1. Its purpose is to insulate the inner conductor, which is at a high-voltage potential during operation of the high-voltage bushing and the high-voltage device, from the surrounding area, which is at ground potential, including the wall of the high-voltage device.

[0003] In general, the wall can be the wall of a transformer tank or the wall of a valve room for a power converter. The voltage to be insulated between the inner conductor and the ambient air can be above 500 kV, and in some applications even 800 kV or more. The voltage to be insulated sometimes also determines the axial length of the high-voltage bushing or insulating body, as well as its radius. The design of the high-voltage bushing accordingly also influences its weight.

[0004] In the event of a fault in the electrical high-voltage device or the high-voltage bushing itself, the high-voltage bushing may become very hot (and thus, for example, . This type of heating can have an undesirable, negative impact, particularly on the mechanical stability of the high-voltage bushing. In the event of a failure of the strength, the high-voltage bushing can break off from the wall to which it is attached and cause further damage in the vicinity of the high-voltage equipment. Usually, a precautionary increase in the mechanical stability of the high-voltage bushing is achieved by over-designing, i.e. . This is achieved by increasing the diameter of the inner conductor. However, this has the disadvantage of further increasing the weight and cost of the high-voltage bushing.

[0005] EP 3 229 242 A1 discloses a high-voltage bushing which is characterized by a moisture-proof housing that encloses the insulating body from the head end to the mounting flange.

[0006] KR 20180018248 A discloses an assembly with a plastic pipe passing through a metal wall. The assembly includes an inner and an outer sleeve enclosing the plastic pipe for fire protection purposes.

[0007] The object of the invention is to propose a high-voltage bushing of the type which is as cost-effective and reliable as possible.

[0008] This object is achieved by a high-voltage bushing according to claim 1. The protective device advantageously prevents the mechanical construction of the high-voltage bushing from losing its strength due to heating, thus preventing the entire high-voltage bushing from forming a solid assembly. At the same time, the high-voltage bushing does not need to be significantly enlarged, thus avoiding a significant increase in weight and cost.

[0009] The shielding cap may be cylindrical or similar and mechanically connected to the housing. It conveniently extends axially between the first and second ends of the high-voltage bushing.

[0010] Particularly when the housing is cylindrical, the shielding hood can be cylindrical or tubular and arranged concentrically around the housing. A cylindrical design is also understood as such if, for example, the tube or cylinder is not complete, but rather, while retaining its basic shape, has slots or recesses, such as a longitudinal slot along its entire axial length.

[0011] Preferably, a radial distance of 50 mm to 300 mm, more preferably 100 mm to 200 mm, is provided between the housing and the shielding cap, so that an intermediate space is formed between the housing and the shielding cap. The housing can generally be made of aluminum, for example, or comprise such. The distance between the housing and the shielding cap makes it possible to slow down thermal transfer. In principle, it is not absolutely necessary for the thermal protection to permanently maintain the mechanical stability of the high-voltage bushing. For most applications, it may be sufficient if the strength of the high-voltage bushing is maintained for a certain period of time until appropriate countermeasures, such as fire extinguishing or other type of fault clearance, are successful. In principle, the intermediate space could be gas-filled (air-filled) or even evacuated.To create the gap, the shielding hood can be connected or attached to the housing using suitable spacers.

[0012] The shielding cap is preferably made of steel, particularly preferably stainless steel, and most preferably an alloyed stainless steel, such as stainless steel alloyed with tungsten (or, for example, molybdenum, vanadium, or cobalt). This choice of material for the shielding cap has the advantage of particularly good heat resistance.

[0013] According to one embodiment of the invention, the protective cover completely covers the mounting flange radially outward. Accordingly, the shielding cover extends axially such that the mounting flange is covered on the outside by the shielding cover. This has the particular advantage that the mounting flange is also thermally protected by the shielding cover. However, radial coverage does not necessarily mean that the mounting flange is completely enclosed by the shielding cover on all sides.

[0014] According to the invention, the shielding cap is arranged to form a gap between the shielding cap and the housing. The gap is at least partially filled with a refractory material. A material is considered refractory within the scope of the invention if its mechanical strength is maintained at least at 600°C. Examples of refractory materials include ceramics, glass, mineral fibers, refractory metals, and precious metals.

[0015] According to the invention, the refractory material comprises magnesium oxide and / or ceramic. These materials advantageously exhibit very good electrical insulating properties.

[0016] According to one embodiment of the invention, the insulating body is impregnated with a resin. In general, the high-voltage bushing can have an insulating body made of resin-impregnated paper (RIP). The insulating body can comprise a capacitor winding. The capacitor winding comprises special paper impregnated with epoxy resin under vacuum. Conductive inserts made of aluminum foil are expediently inserted between these during the winding process. These control inserts serve to control the electric field and, thanks to their good conductivity, ensure optimal voltage distribution even during rapid voltage changes. Such a high-voltage bushing has particularly good dielectric properties. On the other hand, in the case of such a high-voltage bushing, it is particularly important to provide thermal protection for the insulating body.High-voltage bushings of this type can, for example, be designed for the direct connection of transformers to SF6-insulated encapsulated high-voltage switchgear.

[0017] According to one embodiment of the invention, the high-voltage bushing is a transformer bushing. The high-voltage bushing thus serves to (electrically insulate) an electrical line (transformer winding) running inside the transformer from the transformer tank (transformer housing). Accordingly, the high-voltage electrical device is a high-voltage transformer, and the electrical conductor of the high-voltage electrical device is a transformer winding of the high-voltage transformer. The transformer windings of high-voltage transformers are often electrically insulated using insulating oil. Accordingly, the transformer tank is at least partially filled with the insulating oil. However, such insulating oil is relatively flammable, so that a fire may develop in the event of a transformer failure.For this reason, thermal protection of the high-voltage bushing is particularly advantageous.

[0018] The invention further relates to a high-voltage electrical device with a high-voltage transformer, wherein a transformer winding of the high-voltage transformer is led out of a transformer housing of the high-voltage transformer by means of a high-voltage bushing. The high-voltage bushing comprises an inner conductor, which is led through an insulating body and whose first axial end is provided for connection to an electrical conductor of a high-voltage electrical device and whose second axial end is provided for connection to another electrical line, a housing that at least partially encloses the insulating body on the outside, and a fastening flange for fastening the high-voltage bushing to a wall of the high-voltage device.

[0019] Such a high-voltage device is known from the aforementioned WO 2019 / 011426 A1.

[0020] The object of the invention is to provide such a high-voltage device that is as cost-effective and reliable as possible.

[0021] The object is achieved according to the invention in a high-voltage device of the type in question by a protective device for thermal protection of the high-voltage bushing, wherein the protective device comprises a shielding hood which at least partially encloses the housing and / or the fastening flange from the outside.

[0022] The advantages of the high-voltage device according to the invention arise in particular from the advantages already discussed which result from the use of the high-voltage bushing according to the invention.

[0023] According to one embodiment of the invention, the high-voltage transformer is a converter transformer. A converter transformer is part of a converter system. Typically, a converter transformer is located in the immediate vicinity of a valve room in which converter valves of a converter are arranged. With such an arrangement, there is a risk that, if the strength of the high-voltage bushing fails, the high-voltage bushing will break from its anchorage on the transformer and tear a hole in the valve room through which a fire, possibly originating from the transformer, can penetrate unhindered into the valve room. For this reason, the thermal protection of the high-voltage device according to the invention is particularly advantageous in this application.

[0024] The invention is described below with reference to Figures 1 to 3 further explained. Figure 1shows an embodiment of a high-voltage device according to the invention in a schematic representation; Figure 2 shows an embodiment of a high-voltage bushing according to the invention in a schematic representation; Figure 3 shows a further embodiment of a high-voltage bushing according to the invention in a schematic representation.

[0025] In Figure 1 A high-voltage device 1 is shown. The high-voltage device 1 comprises a high-voltage transformer 2, which in the example shown is a single-phase converter transformer. The high-voltage transformer 2 comprises a transformer tank 3, through the wall of which a high-voltage line (connected to a transformer winding) is led out by means of a first and a second high-voltage bushing 4 and 5, respectively.

[0026] In Figure 2A high-voltage bushing 10 is shown. The high-voltage bushing can be used, for example, in the high-voltage device 1 of the Figure 1 The high-voltage bushing 10 comprises an insulating body 11 made of resin-impregnated paper and conductive control inserts. An inner conductor 13 is passed through the insulating body 11 along a longitudinal axis 12. A first axial end 14 of the inner conductor 13 is provided for connection to an electrical conductor of the high-voltage device. A second axial end 15 of the inner conductor 13 is provided for connection to another electrical line.

[0027] The high-voltage bushing 10 comprises a housing 16 made of aluminum, which is arranged cylindrically around the axis of symmetry 12 and encloses the insulating body 11. The high-voltage bushing 10 also has two screw rings 17 and 18 and a mechanical reinforcement 19 with reinforcement ribs. A mounting flange or flange plate 20 is provided for mechanically connecting the high-voltage bushing 10 to a housing of a high-voltage transformer.

[0028] A protective device 21 is provided for thermal protection of the high-voltage bushing 10. The protective device 21 comprises a shielding cap 22, which is cylindrical or tubular and arranged concentrically to the housing 16 around the insulating body 11. The shielding cap 22 is made of stainless steel. The radial distance between the housing 16 and the shielding cap 22 is 150 mm in the example shown, creating a gap 24. The gap 24 is filled with a fire-resistant material 23, magnesium oxide in the example shown. The shielding cap 22 extends axially essentially between the first end 15 of the inner conductor 13 and the mounting flange 20, but without enclosing the latter externally.

[0029] In Figure 3 a high-voltage bushing 25 is shown, which corresponds to the high-voltage bushing 10 of the Figure 2is largely similar. Identical and similar elements and components of the high-voltage bushings 10 and 25 are each provided with the same reference numerals. For the sake of clarity, only the differences between the high-voltage bushing 25 and the high-voltage bushing 10 will be discussed in more detail below.

[0030] The high-voltage bushing 25 has a shielding cap 26 which, in contrast to the shielding cap 22 of the Figure 1 is axially extended. The shielding hood extends axially over the mounting flange 16, so that the latter is radially covered or externally enclosed by the shielding hood 26. For this purpose, the intermediate space 24 is enlarged; its radial width is 155 mm in the example shown. In this way, effective thermal protection can also be provided for the mounting flange 20.

Claims

1. A high-voltage feedthrough (10) having - an inner conductor (13) which is fed through an insulating body (11), - a housing (16) which at least partially encloses the insulating body (11) on the outside, - a fixing flange (20) for fixing the high-voltage feedthrough (10) to a wall of a high-voltage device, characterized by a protective device (21) for a thermal protection of the high-voltage feedthrough (10), wherein the protective device (21) comprises a shield cover (22) which at least partially encloses the housing (16) and / or the fixing flange (20) from the outside, wherein the shield cover (22) is arranged to form an intermediate space (24) between the shield cover (22) and the housing(16), wherein the intermediate space (24) is at least partially filled with a fireproof material (23) which comprises magnesium oxide and / or ceramic.

2. The high-voltage feedthrough (10) as claimed in claim 1, wherein the shield cover (21) is tubular in shape and is arranged concentrically around the housing (16).

3. The high-voltage feedthrough (10) as claimed in claim 2, wherein a radial distance of 50 mm to 300 mm, preferably 100 mm to 200 mm, is provided between the housing (16) and the shield cover (22), so that an intermediate space (24) is formed between the housing (16) and the shield cover (22).

4. The high-voltage feedthrough (10) as claimed in one of the preceding claims, wherein the shield cover (22) is made of steel, preferably stainless steel.

5. The high-voltage feedthrough (10) as claimed in one of the preceding claims, wherein the shield cover (22) completely covers the fixing flange (20) on the outside in a radial manner.

6. The high-voltage feedthrough (10) as claimed in one of the preceding claims, wherein the insulating body (11) is impregnated with resin.

7. The high-voltage feedthrough (10) as claimed in one of the preceding claims, wherein the high-voltage feedthrough (10) is a transformer feedthrough which is set up to feed a transformer winding of a high-voltage transformer out of its transformer housing in an insulated manner.

8. An electrical high-voltage device (1) having a high-voltage transformer (2), wherein a transformer winding of the high-voltage transformer (2) is fed out of a transformer housing (3) of the high-voltage transformer (2) by means of a high-voltage feedthrough (4, 5) as claimed in one of the preceding claims.

9. The high-voltage device (1) as claimed in claim 8, wherein the high-voltage transformer (2) is a power converter transformer.