CN115917679A

CN115917679A - Bushing shield system and use thereof in an outlet insulation system of a high-voltage transformer

Info

Publication number: CN115917679A
Application number: CN202080102204.XA
Authority: CN
Inventors: P·艾史唐德; G·斯特隆伯格; A·埃德林; M·维克斯滕; J·斯科格隆
Original assignee: Hitachi Energy Switzerland AG
Current assignee: Hitachi Energy Co ltd
Priority date: 2020-06-19
Filing date: 2020-06-19
Publication date: 2023-04-04
Also published as: WO2021254639A1; EP4169046A1

Abstract

The present application relates to a bushing shield system (80), a tower assembly with a bushing shield system and a slip-free mounting arrangement for mounting a bushing shield system within a tower assembly of a high voltage transformer. The bushing connection shielding system comprises a shielding tube (1) having a balancing ball (6) at an upper end of the shielding tube (1), said balancing ball (6) being configured to electrically shield a lower end (5) of a connected high voltage bushing. The shielding tube (1) is covered by paper (2) and an electrical shield formed by a dielectric barrier layer comprising at least one barrier layer (3) is provided to the balancing ball (6). A seamless interface is provided between the paper (2) and the at least one dielectric barrier layer (3), wherein at least a lower end (32) of the dielectric barrier layer (3) is integrated in the paper (2).

Description

Bushing shield system and use thereof in an outlet insulation system of a high-voltage transformer

Technical Field

The present invention relates generally to bushing connection shielding systems, and in particular to the connection of bushings to high voltage power transformers. In particular, the bushing shield system is preferably arranged in a pylon assembly (winding assembly) of a high-voltage transformer in order to prevent a creepage path at the transformer-side connection end of the bushing. The shielding system preferably comprises a plurality of barriers that are seamlessly connected with the paper cover of the central insulating tube.

Background

High Voltage (HV) bushings are connected to the power transformer tank, either directly or indirectly through the tower, where certain requirements, including tank size, are typically fulfilled using the tower. In particular, for connecting the bushing to the power transformer, an outlet insulation system (EIS) is provided, which comprises an insulation member connection element between the high voltage winding end of the transformer and the bottom end of the bushing.

The high voltage winding ends may be positioned at the top or in the middle of the axial height of the coil. It is common practice for the outlet insulation system to be connected to the lower end of the casing by a tower. The bushing is designed to withstand the strength of the electric field generated in the insulation, especially when any grounded material is present nearby. As the strength of the electric field increases, leakage paths may form within the insulation of the bushing or at any connection end of the bushing. For example, the risk of leakage paths occurring may increase upon thermal expansion or vibration.

In high voltage transformers, both the bushing and the connection of the bushing to the transformer must be designed to avoid leakage paths. Fig. 7 shows a prior art design for connecting a bushing (not shown) from the top to an oil power transformer. The metallic shielding tube 90 is used to shield the current carrying conductor from the winding to the bushing. The metal shielding tube 90 is fixed inside the tower by means of a support 91. The oil side or bottom end of the sleeve is connected to the metal shield tube by a balance ball or shield 92. However, since the metallic shielding tube 90 and the shield 92 are made of different parts, there is a risk that a gap (shown by wavy line 93) occurring between these parts is excessively large and/or a creepage path for electrical flashover is generated. This may result in a risk of flashover between the shield tube and the balance ball and a low electrical safety.

Accordingly, in view of the above, there is a need for an improved connection shielding system that overcomes at least some of the problems of the prior art.

Disclosure of Invention

In view of the above, a bushing shield system, a no-slip mounting arrangement for a bushing shield system and a tower assembly with a bushing shield system mounted within the tower assembly and a power transformer with an outlet insulation system according to the independent claims are provided. Further aspects, advantages and features are apparent from the dependent claims, the description and the accompanying drawings.

In particular, according to the invention, the concentric metal shielding tubes covered with paper are supported by a non-slip mounting arrangement. According to additional or additional aspects, the paper covered concentric metal shield tube is integrated with a balance ball that electrically shields the high voltage bushing end connections. According to additional or additional aspects, the dielectric barrier separated by the spacer is integrated with the duct paper, thereby forming a seamless interface between the paper and the barrier.

In the prior art, when the shield tube and the balance ball are separated, a gap between the shield tube and the balance ball may cause a risk of electrical flashover or partial discharge. By seamless integration, particularly in combination with improved non-slip support of the shield tube, this gap is eliminated and the electrical strength of the insulation system is improved.

Such an electrical shield of the high voltage bushing end connection may be used inside electrical equipment, for example for high voltage transformers. According to an aspect of the present disclosure, there is provided a bushing connection shielding system, the system comprising a shielding tube having a balancing ball at an upper end thereof, the balancing ball being configured to electrically shield a lower end of a connected high voltage bushing.

The shielding tube is covered by paper, preferably by a plurality of layers of paper, and an electrical shield is preferably provided to the balance ball at its upper end, the electrical shield being formed by a dielectric barrier comprising at least one, preferably three or more, barrier layers.

A seamless interface is provided between the paper and the at least one dielectric barrier layer, wherein at least a lower end of the dielectric barrier layer is integrated in the paper. Preferably, the barrier layer is at least partially sandwiched between different paper layers. Also preferably, the barrier layer comprises a plurality of legs or protrusions at its lower end, which may be integrated in the paper layer and/or closely follow the contour of the shielding tube and/or the balancing ball.

The shielding tube is preferably a metal tube concentrically covered by a plurality of paper layers, preferably oil-impregnated paper layers.

The dielectric barrier layer may include a plurality of dielectric barrier layers separated at a lower portion by a spacer and a paper layer. Preferably, the spacer is arranged at a position more upward than the paper layer.

The dielectric barrier layer is preferably formed from an oil-impregnated pressed plate. The spacer is preferably formed from an oil-impregnated pressed plate.

Furthermore, the spacer may be elongated and extend substantially in the axial direction of the tube, in particular between the top of the balancing ball and the top end of the paper, and preferably a plurality of spacers are circumferentially spaced apart.

The balancing ball is preferably fixed to or integrated with the metal shielding tube, wherein the balancing ball preferably comprises a lower conical section, a middle cylindrical section and/or a substantially dome-shaped upper section.

The barrier layer may be a dome-shaped ring having leg members at a lower end of the barrier layer. The leg member may be clipped into the paper and extend along a portion of the intermediate cylindrical section and/or along a portion of the conical section. Preferably, the leg member is curved along the conical section of the balancing ball.

The shielding tube, the conical section, the cylindrical section and/or the dome-shaped upper section are preferably made of the same material, preferably of metal. A press plate layer, preferably an oil-impregnated press plate layer, may additionally be applied at the outer surface of the dome-shaped upper section of the balancing ball.

According to additional and/or alternative aspects of the present invention, a non-slip mounting arrangement for supporting the above-described system is provided.

The mounting means preferably comprises: a mounting device clamp, which may be configured to be secured inside a transformer or a tower assembly; and mounting the device insulator.

The mounting device clamp supports the mounting device insulator, and the mounting device insulator supports the bushing-coupled shielding system.

The outermost layer of the mounting device insulator of the non-slip mounting device may comprise at least a protrusion, which may extend partially or fully around the circumference of the mounting device insulator. The projection is preferably supported by at least one fixture securing means secured to the mounting device fixture.

The non-slip mounting arrangement may further comprise a stop ring for axially supporting the sleeve joint shielding system.

The stop ring may further comprise a stop ring band for securing the stop ring to the cannula connection shielding system. This stop ring may be made of one part or two or more parts. It may extend completely or partially around the mounting means.

In particular, the snap ring may be adapted to extend circumferentially around an outermost layer of the paper cover of the bushing shield system at a transition region between the cylindrical region of the shield tube and the lower conical section of the balancing ball.

Furthermore, the stop ring may comprise a circumferential groove for receiving a stop ring band. The stop ring may also include an inner support surface for supporting the conical section of the bushing shield system and a lower support surface for being supported by the mounting device insulator.

The mounting device insulator preferably comprises a plurality of circumferentially arranged barrier layers separated by spacers. The spacer may comprise a hook spacer, preferably comprising lower hooks for supporting the inwardly disposed barrier layer and upper hooks for being supported by the outwardly disposed barrier layer.

The radially inner barrier layer may be supported by the nearest or adjacent radially outer barrier layer, and the radially innermost barrier layer may be adapted to cover or surround (partially or fully) the shielding tube.

Additionally, the radially outermost barrier layer may be supported by a clip fixture.

In the context of the present invention, a tower assembly of a high voltage transformer may be provided with a bushing connection shielding system as described herein, preferably by means of a mounting arrangement as discussed herein, provided within the tower assembly.

The invention also provides a power transformer having an outlet insulation system EIS with a connection element for connection between a high voltage winding end and a bottom/lower bushing end of the transformer, and a bushing connection shielding system as described herein, preferably mounted in the transformer by a non-slip mounting arrangement as discussed herein.

Briefly, the present invention provides a shield system that may be used, for example, to shield oil side bushing end connections. The design of the present invention provides a seamless integration of the paper cover and barrier. In particular, according to the invention, at least one, preferably a plurality of external barriers are integrated in the paper layer covering the metal tube. This configuration creates a seamless passage from the paper cover to the barrier, avoiding the creation of a creepage path in the transition. Since the barrier of the present invention is preferably seamlessly integrated into the paper layer, the possibility of flashover between the shielding tube and the balancing ball is reduced or even eliminated, thereby achieving an improvement in electrical safety.

Additionally, the present invention provides, individually and in combination, a slip-free mounting arrangement for a cannula shielding system. This allows in particular a proper and reliable positioning of the shielding tube and the balancing ball with respect to the bushing and thus further improves the shielding, reduces the risk of flashovers and further improves the electrical safety.

Drawings

In order that the above-recited features of the present disclosure can be understood in further detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to preferred embodiments. The drawings relate to preferred embodiments of the disclosure and are described below:

FIG. 1 shows a schematic partial cross-sectional view of a preferred embodiment of the present shielding system;

figure 2a shows a side view of the tower,

FIG. 2b shows a cross-sectional view of a tower with a sleeve connection shielding system inside the tower;

figure 3a shows a cross-sectional view of a bushing connection shielding system,

FIG. 3b shows a side view of the system of FIG. 3 a;

FIG. 3c shows an enlarged view of the top of FIG. 3 a;

FIG. 4a shows a perspective side view of a bushing shield system and a non-slip mounting arrangement;

FIG. 4b shows a cross-sectional view of a bushing shield system with a mounting device;

FIG. 4c shows a top view of the ferrule connection shield system;

FIG. 5a shows a side view of the barrier layer;

FIG. 5b shows a top view of the barrier layer;

FIG. 6 shows a perspective view of a bushing shield system mounted to the non-slip mounting arrangement of the present invention;

fig. 7 shows a prior art bus connection shield arrangement.

Detailed Description

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. The present disclosure is intended to encompass such modifications and variations.

In the following description of the drawings, the same reference numerals denote the same or similar components. Generally, only the differences with respect to the various embodiments are described. Unless otherwise stated, descriptions of parts or aspects in one embodiment may also apply to corresponding parts or aspects in another embodiment.

Referring exemplarily to fig. 1, a schematic partial cross-sectional view of a preferred embodiment of the present bushing shield system (hereinafter also referred to as shield system or just system) is depicted. A preferably cylindrical shielding metal tube 1 is arranged around an electrical conductor (not shown). The shielding tube 1 is connected to the balance ball 6 or is formed integrally with the balance ball 6. Fig. 1 shows only a part of a metal tube 1 with an integrated balancing ball 6. The balancing ball 6 is preferably hollow on the inside, so that the balancing ball is preferably formed by the outer wall. The balancing ball 6 preferably comprises a lower conical or tapered section 61 extending radially outwardly with respect to the tube 1, which lower conical or tapered section is connected to or integrally formed with the cylindrical tube 1. It is further preferred that a substantially cylindrical section 62 is formed on top of the conical section 61. Furthermore, it is further preferred that the (lower) conical section 61, the cylindrical section 62 and/or the tube 1 are formed of the same material (e.g. metal).

As shown in the cross-sectional view of fig. 1, and as can be seen, for example, in the perspective view of fig. 6, a substantially dome-shaped upper section 63 is provided on top of the cylindrical section 62. According to a preferred embodiment, said dome-shaped section 63 comprises a central hole 64 at the top, which is configured to receive and accommodate the end 5 of the high voltage bushing. According to a preferred embodiment, said dome-shaped upper section 63 is preferably also formed of the same material as the metal tube 1, and is preferably additionally covered at the outer surface by a pressed plate element 35 (preferably an oil-impregnated pressed plate element), so as to assume a dome shape corresponding to one of the dome-shaped sections 63. The dome-shaped section 63 may be integrally formed or connected to the cylindrical portion 62. The pressing plate element 5 may be mounted directly on the metal dome portion.

The diameter of the lower conical section 61 of the balancing ball 6 preferably increases in the axially upward direction.

The metal tube 1 is concentrically covered by paper 2, preferably by a plurality of layers of oil-impregnated paper. The oil impregnation may typically occur after manufacture and assembly, for example when the transformer is filled with oil. The paper and the pressboard are preferably not impregnated at the time of application. Mounting means 7 are provided for supporting the shielding system 80 and preferably supporting the tube 1 at the paper 2 covering the metallic shielding tube 1. For example, the mounting device 7 is used for mounting the shielding system 80 within a tower or a tower assembly, such as shown in fig. 2 b. Preferably, the mounting means is a non-slip mounting means according to a preferred aspect of the present invention, which will be discussed in further detail below.

The bottom or oil side end 5 of the bushing is connected to a current carrying cable. Preferably, the sleeve is not connected to the balance ball 6, wherein such connection is preferably shielded by the novel design of the connection shielding system 80.

It should be noted that the present application relates to upper and lower portions which are understood to relate to relative positions with respect to gravity, that is, with respect to gravity, the upper portion is above the lower portion as shown. However, the invention is not limited to an orientation exactly aligned with the gravitational field, so that in case of a tilted orientation or even a downward orientation of the system, the terms "upper", "top" may be replaced by "distal", and "lower", "bottom" may be replaced by "proximal". In the latter case, an additional taper provided in the end (downward in the figure) of the shield tube to mate with the stop ring as discussed herein. In this case, the near side may mean closer to the high voltage power transformer. However, for simplicity, a typical preferred substantially vertical orientation of the system will be discussed in the examples.

The shielding system 80 comprises at the upper section 63 a dielectric barrier 3 or barrier layer 3 separated by spacers 4. The spacers 4 are preferably vertically oriented from top to bottom, or vice versa, and are preferably circumferentially spaced, preferably in a regular pattern or distribution, as shown for example in fig. 6. For example, FIG. 6 shows spacer assemblies 4 that are circumferentially spaced apart. The remainder is preferably annular and extends circumferentially around the bore of the system.

The barrier 3 is integrated seamlessly in the layer of the paper cover 2, which avoids any gaps. Such a seamless interface is preferably achieved by winding a plurality of paper layers at different radial levels around the lower end 32 of the barrier 3 (compare fig. 5). The barrier 3 is preferably formed from a pressed plate (preferably an oil-impregnated pressed plate) and is preferably dome-shaped as shown.

The embodiment shown shows four barriers 3. However, it is possible according to the invention to use fewer or more barrier layers, for example only 2 or 3 barrier layers, or 5, 6, or even more barrier layers. The person skilled in the art will preferably adjust the number of barrier layers in dependence of the voltage or potential difference provided at the bushing end connection.

Fig. 5a and 5b show side and top views of a single barrier layer 3. Preferably, the barrier layer 3 is a dome-shaped barrier layer having a central aperture 31 in annular plan view for receiving the bottom end of the bushing. The diameter of the hole 31 in the barrier is substantially the same as the diameter of the central hole 64 in the dome-shaped section 63 of the balancing ball 6. At the lower end of the barrier 3, a plurality of, preferably a single, extensions 32 are provided, in the form of arms, legs, leg members or tines. These may further facilitate wrapping the paper layers around them for seamless connection to the paper cover 2 and bending of these portions of the barrier layer 3, for example along the conical section 61 of the balancing ball 6 (see, e.g., fig. 1).

As mentioned above, the lower leg member 32 of the barrier layer 3 is preferably integrated seamlessly in the paper cover 2, preferably at the lower conical section 61 of the balancing ball and preferably also at the cylindrical middle section 62 of the balancing ball 6. The upper parts of the barrier layer 3, preferably dome-shaped, are preferably separated from each other by a plurality of spacers 4, and are preferably separated from the paper cover 2 by being axially spaced. The space between the vertically oriented elongated spacer 4 and the barrier layer 3 at the upper part is left empty or may be filled with additional filling material.

The design of the invention is preferably used for electrical shielding of high voltage bushing end connections, for example inside electrical equipment, such as high voltage transformers, preferably AC high voltage oil transformers or reactors. For example, the configuration of the invention may be used for oil-filled transformers, which typically comprise an outlet insulation system (EIS) on a top or middle outlet system with a tower assembly for connecting the windings of the transformer to the bushings. It is therefore preferred that the bushing end connection shield can be used at more than 200kV, more than 400kV, more than 800kV or even up to 1200kV or even higher.

In general, the bushing shield system may be used with any type of outlet insulation system. In particular, the outlet insulation system (EIS) comprises an insulation component and a connection element between the high voltage winding end and the bottom of the bushing end. The high voltage winding ends may be positioned on top or in the middle of the axial height of the coil. It is common practice for each outlet insulation system to pass the phase current through the inside of the tower or main box to the bottom end of the bushing. The tower diameter depends on the system voltage and EIS design. For example, the determination of the tower diameter must affect the amount of steel, mineral oil, etc., and by making a large oil gap a smaller oil gap is important for both the material cost and the weight and size of the transformer. Furthermore, common locations for EIS are in the tower or box of the transformer, and/or connections to the windings may be at the top or middle of the windings at each location.

For example, fig. 2a shows a perspective view of a tower or tower assembly 400 of a high voltage transformer, wherein fig. 2b shows a shielding system 80 mounted inside the tower assembly by a mounting device 7 comprising a mounting device clamp 200 and a mounting device insulator 100 (see, e.g., fig. 6). According to the present invention, it is preferable that the bottom end of the sleeve is not connected to the balance ball 6. In contrast, the present invention provides a design in which the balance balls 6 are fixed to or formed integrally with the shield tube 1. Thus, to fix the position of the shielding system 80 within the tower assembly 400, it is preferred that the shielding system 80 of the present invention itself be secured by the non-slip mounting means 7, rather than indirectly by a bushing connection. In the sense of the present invention, no sliding means that vertical movements of the system 80 are greatly reduced or even avoided. This allows for a precise positioning of the shielding system 80 with respect to the sleeve 5 and avoids severe misalignment.

Figures 3a to 3c show the bushing connectivity shielding system 80 in more detail. In particular, fig. 3b shows a side view of the system 80, wherein the lower shielding tube 1 is concentrically covered by the paper 2 and the upper part comprises a balancing ball 6 with a conical or tapered section 61. Preferably, the balancing ball 6 comprises a tapered/conical lower section 61, a substantially cylindrical intermediate section 62 and/or a substantially dome-shaped upper section 63 (see, e.g., fig. 1 and 7). The dome-shaped upper section 63 comprises a central upper hole 31 to receive and accommodate the sleeve bottom end 5. The barrier 3 comprises corresponding holes 31, which are substantially concentric. As is clear from the perspective views of fig. 6 and 4a to 4c, the entire system 80 is substantially rotationally symmetrical around the central axis a of the shielding tube 1.

Fig. 3a shows a cross-sectional view of a system 80, wherein the shaded layer 2 around the shielding tube 1 is formed by a plurality of oil-impregnated paper layers concentrically wound around the tube 1. Likewise, the lower conical section 61 of the balancing ball 6 is preferably only covered by the paper layer 2. The middle section 62 is preferably covered by a seamless transition of the paper 2 and the barrier layer 3, and the upper or top section 63 is preferably shielded only by the barrier layer 3. The

individual layers

2 and 3 and the covering/shielding of the balancing balls 6 are shown in more detail in fig. 3 c.

Fig. 4a to 4c show the system 80 mounted to the mounting device 7, comprising a mounting device clamp 200 and a mounting device insulator 100, in a side view (fig. 4 a), a cross-sectional view (fig. 4 b) and a top view (fig. 4 c). Preferably, the mounting device 7 comprises an upper clamp 200 and a lower clamp 200, which are preferably identical or similar. Details of the mounting means 7 are also discussed with reference to fig. 6.

Fig. 6 shows a perspective schematic view of the bushing shield system 80 mounted to the mounting device clip 200 via the mounting device insulator 100. The mounting device insulator 100 includes a substantially cylindrical outer shape that is supported by correspondingly (concavely) formed (upper) and (lower)

clamp brackets

222, 220. The upper fixture 212 and the lower fixture 210 are connected to

corresponding jig brackets

222, 220, respectively. Preferably, the upper fixture 212 and the lower fixtures 210 are formed as belts.

As shown in fig. 6, and also in fig. 4a, the outer surface of the outermost mounting device insulation barrier 110 includes

barrier protrusions

112 and 114. The

barrier projections

112, 114 may be fixed to the outer surface of the mounting insulator, for example by gluing or the like, or may be integrally formed therewith.

Barrier projections

112 and 114 may be (further) secured to the external mounting device insulation by straps 120. In any case, such a tape is preferably foreseen for connecting the mounting means insulation barrier 110c, which may be formed by two halves. The advantage of providing such a protrusion can be derived from fig. 6, which shows that this protrusion can form a shoulder supported by the fixtures 212 and 214. In particular, the upper barrier projection 114 is supported by an upper jig fixing device 212 located below the upper barrier projection 114, and the lower barrier projection 112 is supported by a lower jig fixing device 210. In other words, a downwardly directed gravitational force results in a suspended or suspended mounting of the bushing connection shielding system. This type of suspension or suspension mounting facilitates a non-slip mounting arrangement.

The mounting device insulator 100 includes a plurality of mounting device insulation barriers 110a, b, c, d concentrically arranged around each other, with the mounting device insulation barrier 110a constituting an innermost barrier layer and the mounting device insulation barrier 110d constituting an outermost barrier layer (see fig. 1). Advantageously, three, four or more or less barriers may be provided.

Between the different mounting device insulation barriers 110a, b, c, d, a plurality of

spacers

130, 140 are provided, which will be discussed further below. The

spacers

130, 140 are preferably elongated, circumferentially spaced apart, and arranged to extend in the axial direction of the system 80.

To facilitate assembly, the mounting device insulation barriers 110a, b, c, d may be made of a single piece, or may be formed of two halves that may be connected to each other and surround the system 80.

As discussed above, the outermost mounting device insulation barrier 110c/d includes one or two

barrier protrusions

112 and 114 that are supported by the fixtures 212 and 214 of the

clamp brackets

220, 222. Each radially inwardly disposed mounting device insulation barrier 110b, a is supported by a respective next outer mounting device insulation barrier 110c, b.

In particular, as described above, the

spacers

130, 140 are disposed between adjacent mounting device insulation barriers 110d, c, b, a. One type of spacer 140 is substantially S-shaped. In other words, such a spacer 140 includes a radially outwardly extending hook 142 at an upper end thereof and a radially inwardly extending hook 144 at a lower end thereof.

The radially outwardly projecting upper projecting hook 142b of the spacer 140b, which is arranged radially outside the mounting device insulation barrier 110b/c and radially inside the outermost mounting device insulation barrier 110c/d, is adapted to engage with the external mounting device insulation 110c/d, preferably with its upper end, more preferably in a hanging or suspending manner. The corresponding inwardly projecting lower hook 144b preferably supports, at its lower end, further preferably in a supporting manner, the next radially inward mounting device insulating barrier, i.e., the intermediate mounting device insulating barrier 110 b/c. The same function is preferably applied to all hook spacers 140.

As shown in fig. 1, the mounting device insulator 100 further includes a snap ring 126. The stop ring 126 may be made of a single piece or may be constructed of two halves. Preferably, one half of the snap ring extends through an angle of about 180 ° or less, preferably about 170 °. The stop ring 126 includes an angled inner ring surface, preferably angled at an angle a preferably between 10 ° and 30 °, preferably about 20 °. The surface preferably corresponds in orientation to the conical section 61 and serves as an abutment surface. Preferably, the outer ring surfaces are at least partially equiangular. On its outer and/or lower surface, the stop ring is provided with an abutment surface for abutment against, for example, the innermost barrier 110a and/or the

spacers

130, 140.

In its mounted position, the stop ring 126 is formed (at least partially) circumferentially around the outer surface of the paper cover 2 at the transition between the substantially cylindrical region of the tube 1 and the lower conical section 61 of the balancing ball 6.

Thus, the force of the system 80 (primarily gravity) may be supported via the stop ring 126, on which a portion of the conical section 61 of the system rests. On the other hand, the snap ring 126 is supported by the mounting device insulator 100. Preferably, the snap ring 126 is supported by the innermost mounting device insulator 110a and/or the innermost hook spacer 140. In other words, the entire bushing shield system 80 can be hung with its hook members on the suspension arrangement of the mounting device insulator 100, wherein the mounting insulator 100 is supported by the mounting device clip 200. By this arrangement, a substantially slip-free mounting is achieved, allowing for a precise positioning of the cannula connection shielding system 80, in particular with respect to the cannula 5.

This configuration specifically allows gravity-downward directed forces of the bushing shield system 80 to be transferred to the suspension design via the stop band 124, via the mounting device insulation barrier 110 and hook spacer 140, and finally via the

barrier protrusions

112 and 114.

The structure of the mounting device insulator 100 is illustrated in fig. 1, which shows different radial layers of the mounting device insulator 100, e.g., consistent with the discussion above. Figure 6 shows the entire mount insulation with all "layers". The mounting device insulation barrier 100 is preferably formed from a pressed plate, preferably an oil-impregnated pressed plate.

In the three-barrier design, the outer mounting device insulation barrier 100c is preferably designed similarly to the middle insulation barrier 100 b. Preferably, the external mounting device insulation barrier 100c and/or the intermediate insulation barrier 100b is formed of two semi-cylinders. Also, the external mounting device insulation barrier 100c may include a barrier mounting protrusion, which is preferably supported by a jig bracket or jig fixture. As shown, for example, in fig. 6, the external mounting device insulation barrier 100c includes two axially spaced apart projections extending circumferentially along the outer surface of the barrier 100 c. In particular, a lower barrier mounting protrusion 112 and an upper barrier mounting protrusion 114.

In fig. 1 and 6, as an example, an (outer) hook spacer 140b is visible. These outer hook spacers 140b are elongated and vertically oriented (extending in the axial direction) and arranged circumferentially spaced apart around the shielding tube 1. At least one, preferably more than one, and further preferably, each hook spacer 140b preferably includes a radially outwardly projecting hook end 142b at an upper end and a radially inwardly projecting hook end 144b. The upper hook end(s) 142b preferably engage the (radially) outer barrier 110 c. Lower hook end 144b preferably engages intermediate barrier 110 b. The additional (outer) spacer 130b may be formed substantially parallel to the (outer) hook spacer 140b. The illustrated embodiment shows spacer 130b between two (outer) hook spacers 140b in the circumferential direction. The spacers 130 may also be formed from a pressed plate, in particular from an oil-impregnated pressed plate. The same applies for (outer) spacers 140b, 130c for (more inwardly) arranged spacers 140a, 130 a.

Similar to the outer hook spacer 140b, the inner hook spacer 140a includes a radially outwardly projecting hook end 142a at an upper end, and preferably also includes a radially inwardly projecting hook end 144a at a lower end.

In fig. 1, the stop ring 126 is visible at the transition between the cylindrical section of the tube and the lower conical/tapered section 61 of the balancing ball 6. It should be noted that the snap ring 126 is mounted to the outermost layer of the paper cover 2. The stop ring 126 is preferably formed from a pressed plate, preferably an oil-impregnated pressed plate.

The bushing connection shielding system of the invention is not limited to the end connection between the bushing and the power transformer, but may also be used for reactors.

While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Reference numerals

1. Shielding tube

2. Paper/paper cover

3. Dielectric barrier

31. Hole(s)

32. Extension part

4. Spacer member

5. End of a high voltage bushing

6. Balance ball

61. Conical lower section

62. Cylindrical intermediate section

63. Domed upper section

64. Center hole

7. Mounting device

71. Supporting ring

80. Sleeve connection shielding system

100. Mounting device insulator

200. Mounting device clamp

110a, b, c (mounting means insulator) barrier (a = inner, b = middle, c = outer)

[ Press plate, oil immersed type ]

112. Lower barrier mounting projection [ supported by lower clamp bracket/lower clamp fixture ]

114. Upper barrier mounting projection [ supported by upper clamp bracket/upper clamp fixture ]

130a, b spacers

140a, b hook spacer

142a, b [ outwardly projecting hook end at upper end ] [ engage with (radially) outwardly arranged barrier ]

144a, b [ inwardly projecting hook end at lower end ] [ engaging/supporting (radially) inwardly disposed barrier ]

210 (lower part) clamp fixing device (belt)

212 (Upper) Clamp fixture attachment (Belt)

220 (lower) clamp support

222 (Upper) jig support

400. Tower assembly

Claims

1. A bushing connectivity shielding system (80), comprising:

a shielding tube (1) having a balancing ball (6) at an upper end of the shielding tube (1), the balancing ball (6) being configured to electrically shield a lower end (5) of a high voltage bushing to which it is connected,

wherein the shielding tube (1) is covered by paper (2) and an electrical shield formed by a dielectric barrier comprising at least one barrier layer (3) is provided to the balancing ball (6);

wherein a seamless interface is provided between the paper (2) and the at least one dielectric barrier layer (3), wherein at least a lower end (32) of the dielectric barrier layer (3) is integrated in the paper (2).

2. System (80) according to claim 1, wherein the shielding tube (1) is a metal tube concentrically covered by a plurality of paper layers (2), preferably oil-impregnated paper layers.

3. The system (80) according to claim 1 or 2, wherein the dielectric barrier comprises a plurality of dielectric barrier layers (3) separated at the lower part by spacers (4) and paper layers (2).

4. A system according to claim 3, wherein the spacer (4) is elongated and oriented to extend substantially in the axial direction of the tube (1) between the top of the shield and the top end of the paper (2), and wherein, preferably, a plurality of spacers (4) are circumferentially spaced.

5. The system (80) according to any one of the preceding claims, wherein the balancing ball (6) is fixed to the metal shielding pipe (1) or integrated with the metal shielding pipe (1), wherein the balancing ball (6) preferably comprises a lower conical section (61), an intermediate cylindrical section (62) and/or a substantially dome-shaped upper section (63).

6. System according to claim 5, wherein the barrier layer (3) is a dome-shaped ring with leg members (31) at the lower end of the barrier layer (3), which leg members are clipped in the paper (2) and extend along a part of the intermediate cylindrical section (62) and/or along a part of the conical section (61), wherein preferably the leg members are bent along the conical section (61) of the balancing ball (6).

7. System according to claim 5 or 6, wherein the shielding tube, the conical section (61), the cylindrical section (62) and/or the dome-shaped section (63) are made of the same material.

8. A slip-free mounting device (7) for supporting the system of any one of the preceding claims, wherein the mounting device (7) comprises:

mounting device clamp (200), and

an insulator (100) of the installation device,

wherein the mounting device clamp (200) supports the mounting device insulator (100) and the mounting device insulator supports the bushing connectivity shielding system (80).

9. The non-slip mounting device (7) as claimed in claim 8, wherein the outermost layer of the mounting device insulator (100) comprises at least one protrusion (112, 114) supported by at least one clamp fixture (210, 212) fixed to the mounting device clamp (200).

10. The non-slip mounting device (7) according to claim 8 or 9, comprising a stop ring (126) for axially supporting the bushing connectivity shielding system (80).

11. The non-slip mounting device (7) according to any one of claims 8 to 10, wherein the stop ring (126) is adapted to extend circumferentially around the outermost layer of the paper cover (2) of the bushing shield system (80) at the transition between the cylindrical region of the shield tube (1) and the lower conical section (61) of the balancing ball (6).

12. The non-slip mounting device (7) as claimed in any one of claims 8 to 11, wherein the stop ring (126) comprises an inner support surface for supporting a conical section of the bushing shield system (80) and a lower support surface for being supported by the mounting device insulator (100).

13. The non-slip mounting device (7) according to any one of claims 9 to 12, wherein the mounting device insulator (100) comprises a plurality of circumferentially arranged barrier layers (110) spaced apart by spacers (130, 140), wherein the spacers comprise hook spacers (140), the hook spacers (140) comprising lower hooks for supporting inwardly arranged barrier layers (110) and upper hooks for supporting outwardly arranged barrier layers (110), and wherein the radially inner barrier layer (110) is supported by the closest radially outer barrier layer (110), and wherein the radially innermost barrier layer (110) is adapted to encase the shielding pipe (1).

14. A tower assembly (400) of a high voltage transformer, the tower assembly (400) having a bushing connection shielding system according to any of claims 1 to 8 inside, preferably by a mounting arrangement according to any of claims 9 to 13.

15. An electrical transformer having an outlet insulation system, EIS, the outlet insulation system comprising:

a connecting element for connection between a high-voltage winding end of the transformer and the bottom/lower bushing end (5), and

a bushing shield system according to any of claims 1-8, preferably mounted in the transformer by a slip-free mounting arrangement according to any of claims 9-13.