EP1577904B1 - High voltage bushing with element for electric-field control - Google Patents

Abstract

A dielectric bushing (1'), particularly a high-voltage bushing comprises an insulator part (2, 2c) with two installation flanges (4, 8) for installing the bushing. Instead of a screening electrode, a non-linear electric and/or dielectric field control element (9, 9i, 9o) is provided in a field stress zone (7, 7a, 7b). The field control element comprises a matrix, particularly epoxy, silicone, ethylene propylene diene monomer, thermoplast, thermoplastic elastomer or glass. The matrix is filled with microscopic varistor particles, particularly doped zinc oxide particles, titanium oxide particles or stannous oxide particles and/or is filled with high permittivity, particularly with BaTiO 3particles or titanium oxide particles.

Description

TECHNICAL AREA

The invention relates to the field of high or medium voltage technology, in particular electrical insulation and connection technology for grounded high voltage apparatus. It is based on a dielectric bushing and a high-voltage electrical apparatus according to the preamble of the independent claims.

STATE OF THE ART

In the WO 02/065486 A1 is a high voltage insulator z. As porcelain or composite material with a coating of field control material (FGM) disclosed. The field-controlling coating consists of varistor powder, z. Of doped zinc oxide (ZnO) embedded in a polymer matrix. The FGM coating serves to compare the field distribution on the insulator surface and is distributed so that part of the material is in electrical contact with both the ground electrode and the high voltage electrode. In this case, the FGM coating can only partially cover the insulator length and be concentrated in the field-loaded electrode regions. The FGM coating can be applied to the insulator surface, can be incorporated there in a shield or can be shielded by a weatherproof, electrically insulating protective layer to the outside. An equalization of the capacitive field load can be realized by alternating horizontal strips or bands of FGM coating and insulator material.

For porcelain insulators, the FGM coating may be applied in the form of a glaze or a paint, or mixed into a slurry or clay, applied to the porcelain insulator and fired there to a glaze or ceramic layer. Alternatively, the matrix for the FGM coating may be a polymer, an adhesive, a casting or a mastic or a gel.

In the EP 1 042 756 discloses a glass fiber reinforced insulator tube which is impregnated on the inner surface and optionally also the outer surface with a resin which has a particulate filler with varistor properties, in particular zinc oxide. The GRP tube can be made by winding a fiberglass mesh which is impregnated with the varistor-filled resin at least on the outer layers.

In the book " The Electric Power Engineering Handbook "by LL Grigsby, CRC Press and IEEE Press, Boca Raton (2001 ), various types of electrical feedthroughs are disclosed in Chapter 3.13, "Electrical Bushings" by LB Wagenaar, pp. 3-171 to 3-184. In particular, in Fig. 3 .151 indicated a passage with a ground-side, arranged within the insulator tube shielding electrode. By the shielding electrode, a field control is achieved in the region of the ground-side mounting flange such that the heavily field-loaded zone is field-relieved at the transition from flange to insulator. Such internal shielding electrodes are in pressure gas-insulated bushings, z. B. in SF ₆ -isolated or air-insulated bushings, especially for high voltage level mandatory. Internal shielding electrodes are also known for solid-insulated feedthroughs. However, the shielding electrodes lead to large diameters of the bushings. In addition, only relatively inhomogeneous field controls are achieved with shielding electrodes compared to capacitor bushings with oil or resin impregnated paper. This must be compensated by larger construction heights for the bushings.

The ABB Power Technology Products AB brochure, "SF ₆ -air bushings, type GGA", Technical Guide, 1996-03-30, discloses dielectric feedthroughs equipped with internal shielding electrodes on the ground flange and, for higher voltage levels, also on the voltage-side flange are.

In the DE 198 44 409 an insulator is shown, which is particularly suitable for dielectric feedthroughs. As usual, the insulator comprises an insulator body made of porcelain or composite material and a porcelain or silicone shield. The shield has a variable insulator screen density. For field relief in a Isolatorendbereich turn the known shield electrode between the insulator body and conductor is present. It is now proposed to install an increased number of insulator screens in the heavily field-loaded area where the shielding electrode ends. Due to the increased insulator screen density, improved field relief is achieved in the end region of the shield electrode.

The invention relates to a prior art, as shown in the US Pat. 3,318,995 is known. There, made of cast resin bushings are disclosed, which remain electrically reliable even with differential thermal expansion or shrinkage due to cavitation between metal and cast resin. For this purpose, regions with increased cracking tendency are electrically shielded by partially conductive or semiconductive field shielding layers. The layers are either arranged on the high-voltage inner conductor and electrically connected to this end; or they are arranged on shielding electrodes and electrically connected to these end, wherein the shielding electrodes in turn are electrically connected to the grounded housing of the connected apparatus. The field shielding layers create a field-free space between themselves and the inner conductor or themselves and the shielding electrode and effectively shield cavities in the casting resin.

PRESENTATION OF THE INVENTION

The object of the present invention is to provide an improved dielectric bushing and a high-voltage electrical apparatus and an electrical switchgear with such a procedure. This object is achieved according to the invention by the features of the independent claim.

The invention consists in a dielectric bushing, in particular a high voltage feedthrough for a high voltage electrical apparatus, comprising an insulator part with a first mounting flange and a second mounting flange for mounting the bushing, wherein within the bushing in a field loading zone in the region of the first mounting flange one for a desired voltage level required Shield electrode is omitted and instead for the purpose of field control in the field loading zone, a non-linear electrical and / or dielectric field control element on the insulator part in the region of the first mounting flange is present and the field control element is in electrical contact with the first mounting flange.

By means of the invention, therefore, it is possible to omit a shielding electrode which is necessary according to conventional technical understanding for a specifiable voltage level. Thereby many advantages are achieved. By omitting the previously necessary existing inner shield electrode dielectric bushings can be thinner, ie built with a reduced diameter. The limit stress, from which a conical widening towards the earth flange is more economical, can be shifted to higher voltage levels. Cylindrical feedthroughs are cheaper to produce than conical ones. The risk of electrical flashovers between adjacent feedthroughs is reduced and adjacent phases may be placed closer to each other or to ground. Finally, better field control is achieved by the inventive field relief by field control material in the flange area than by the conventionally used shielding electrode. The bushings can therefore be built shorter. In particular, in the case of pulse loading, the E-field is no longer concentrated in the region of the shielding electrode during the entire pulse duration, but can propagate as a wave along the field control element and thereby degrade. In addition, the maximum field strengths are reduced.

In a first embodiment, the field control material with respect to its non-linear electrical and / or dielectric properties, its geometric shape and its arrangement on the insulator part for dielectric relief of field loading zone without shielding electrode for all operating conditions, especially for surge voltages designed. The field control element can thus master even the most critical field loading conditions without shielding electrode or shielding electrodes.

In claim 3 design criteria for the electrical design of the field control material are given, by which an advantageous field control can be realized.

In claim 4 and 5 design criteria for geometrical design of the field control element are specified by which an advantageous field control can be achieved with little material. In particular, a minimum required length of the field control element can be determined along the longitudinal extent of the insulator part according to claim 5. It is thereby achieved that the field load propagates as a traveling wave along the field control element, in particular in the case of surge voltage, and thereby degrades to such an extent that no damaging field strengths can form on reaching the remote end of the field control material.

Claim 6 indicates how can be built with the field control element DC feedthroughs in a simple manner.

The embodiment according to claim 7 has the advantage that in particular the highest field loads in the region of the earth flange with the field control material can be controlled.

The embodiments according to claim 8 and 9 have the advantage that both flange regions are protected by the field control materials independently of each other from flashovers or partial discharges.

Claim 10 feature a) indicates various radial positions for the arrangement of the field control material on the insulator part. Claim 10 feature b) has the advantage that a conventional GRP pipe (glass fiber reinforced plastic) or a conventional porcelain insulator by a self-supporting FGM pipe (field control material tube) is replaceable.

Claim 11 specifies advantageous material components for the field control element.

Claims 12 and 13 relate to a high-voltage electrical apparatus and an electrical switchgear comprising an inventive implementation with the above-mentioned advantages.

Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description and the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1a, 1b

show in cross-section conventional high-voltage bushings according to the prior art;

Fig. 2a-2d

show in cross-section embodiments of a FGM passage for a GRP tube with silicone shielding and

Fig. 2a

a continuous FGM coating

Fig. 2b

an earth-side FGM coating

Fig. 2c

each one independent earth-side and high-voltage side FGM coating and

Fig. 2d

an inside and outside FGM coating;

Fig. 3a-3b

show, in cross section and in plan view, embodiments of an FGM feedthrough for a porcelain insulator with inside and optionally outside FGM coating;

Fig. 4

shows in cross section an embodiment of a self-supporting field control element with a silicone shielding;

Fig. 5

shows electrical surface field distributions E (x) calculated as a function of the location coordinate x along the feedthrough and as a function of time for conventional feedthroughs (a, b, c) and for an inventive FGM feedthrough (D, E, F, G ); and

Fig. 6

shows an unfavorable field distribution E (x) if the length or the conductivity of the FGM coating is too short.

In the figures, like parts are given the same reference numerals.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1a shows a conventional gas-insulated dielectric bushing 1, in particular a high voltage bushing 1 for a high voltage electrical apparatus. The bushing 1 comprises an insulator part 2; 2a, 2b with a first ground-side mounting flange 4 for mounting the bushing 1 on a grounded housing 5 of an electrical apparatus (not shown) and a second voltage-side mounting flange 8 for mounting the bushing 1 to a high voltage part (not shown). The insulator part 2; 2a, 2b has a gas space 20 for an insulating gas 20 in the interior. The gas space 20 contains a dielectrically insulating gas 20, e.g. As air, compressed air, nitrogen, SF ₆ or similar gas. It may also be an isolation space 20 for receiving an insulating liquid 20 may be present. The gas-insulated bushing 1 is thus hollow, typically hollow cylindrical, with an axis 3a, for receiving an electrical part 3 or at least one electrical conductor 3 in the gas space 20. The bushing 1 is usually used to connect the encapsulated electrical apparatus to ground potential 5 at High or medium voltage network. As is known, an internal shielding electrode 6, 6a is necessarily present in order to achieve field relief in the field-loaded zone 7, 7a at the lower ground flange 4 and to reduce or avoid partial discharges and flashovers. The shielding electrode 6, 6a is typically in electrical contact 46 with the ground flange 4. It protrudes into the gas space 20 and tapers generally conically upwards. It determines the diameter of the bushing 1 in the Erdflanschbereich 4. Dashed lines indicate a further shielding electrode 6, 6b, which may be arranged in the field-loaded zone 7, 7b at the upper voltage-side flange 8. This too often tapers conically downwards and serves for field control in the field loading zone 7, 7b.

Fig. 1b shows an example of a solid-state implementation 1 according to the prior art. Here, the insulator part 2, 2b is designed as a resin body 2 filled in its entirety with an optional shield 2b. The insulator part 2, 2b thus has an insulation space for a solid insulating material 20 in the interior. 3b and 3c denote the power connections. The insulator part 2, 2b surrounds the current conductor 3. For field control again a shielding electrode 6, 6a in the field loading zone 7, 7a on the earth flange 4 is present and is electrically conductively connected thereto via a contact 46.

Fig. 2a-2d and Fig. 3a-3b show exemplary embodiments of a gas-insulated or solid-insulated or otherwise insulated dielectric bushing 1 ', in accordance with the invention at least one shielding electrode 6; 6a, 6b has been omitted without sacrificing dielectric strength or reliability. Instead of the shielding electrode 6; 6a, 6b is namely for the purpose of field control in the field loading zone 7; 7a, 7b a nonlinear electrical and / or dielectric field control element 9; 9a, 9b; 9i, 9o; 9s on the insulator part 2; 2a, 2b; 2c in the region of the first mounting flange 4 available. The field control element 9; 9a, 9b; 9i, 9o; 9s is used instead of the earlier in the insulator part 2; 2a, 2b; 2c arranged shielding electrode 6; 6a, 6b for the dielectric discharge of the field loading zone 7; 7a, 7b. In the following preferred embodiments will be discussed.

According to Fig. 2a the field control element 9 is designed for the purpose of relieving the field loading zone 7 in such a way that the flange region 7 is stress-relieved. For this purpose, the field control element 9 in an intermediate layer 22 between the GRP pipe (glass fiber reinforced plastic and in particular epoxy tube) 2a and the silicone shield 2b in the form of a cylinder jacket-shaped coating 9 is arranged. In particular, the field control element 9 may be replaced by any known manufacturing or processing process, e.g. B. casting, spraying, winding, extrusion o. Ä., Be applied to the outside of the GRP pipe 2 a.

Preferably, the field control element 9; 9a, 9b; 9i, 9o; 9s on: nonlinear electrical varistor characteristics and in particular a critical field strength, the varistor switching behavior of the field control element 9; 9a, 9b; 9i, 9o; 9s characterized; and / or a high dielectric constant ε, in particular ε> 30, preferably ε> 40 and particularly preferably ε> 50.

Advantageously, the field control element 9 is in electrical contact with the first mounting flange 4 and extends over a predeterminable length l along a longitudinal extension x of the insulator part 2; 2a, 2b. It has a predeterminable thickness d or thickness distribution d (l) as a function of the length l. Preferably, its length l is greater than or equal to a ratio of a maximum test voltage to be tested, in particular a lightning impulse, to the critical electric field strength. This design consideration applies with advantage for all embodiments where the shielding electrode 6a in the Erdflanschbereich 7a by the field control element 9; 9a; 9i, 9o is replaced.

According to Fig. 2b is the field control material 9, 9i disposed on an inner side 21 of the GRP pipe 2a and can additionally help to reduce surface charges there. The length l ₁ is chosen here by way of example so that the field control layer 9, 9i is not in electrical contact with the counter flange 8.

According to Fig. 2c can in addition to the field control 9; 9a another field control element 9; 9b, which likewise has suitable nonlinear electrical and / or dielectric properties, in particular those as previously described for the field control element 9; 9a, and in addition in a field loading zone 7, 7b in the region of the second mounting flange 8 over a predetermined length l; l ₂ and thickness d or d (l ₂ ) on the insulator part 2; 2a, 2b is present. In particular, the further field control element 9 is used; 9b as a replacement for a shielding electrode 6b in the region of the second, here the upper, mounting flange 8. Here is an example of an arrangement of the field control element 9; 9a including the further field control element 9; 9b is selected in the intermediate layer 22. Preferably, the further field control element 9; 9b in electrical contact with the second mounting flange 8 and / or is the further field control element 9; 9b by a field control material-free zone extending along the longitudinal extent of the insulator part 2; 2a, 2b extends from the field control element 9; 9a separated in the region of the first mounting flange 4.

According to Fig. 2d can at the same time a first field control element 9; 9o in the intermediate layer 22 between the GRP pipe 2a and shield 2b and a second field control element 9, 9i on the inner side 21 of the GRP pipe 2a in the Erdflanschbereich 7a be present. This achieves a further improved field control. The first integrated and the second internal field control element 9o, 9i can be made of the same or other field control material and in particular varistor material. The associated thicknesses d _o , d _i and lengths l _o , l _i can be designed individually. By way of example, d _i > d _o and l _i <l _{o are} selected.

Fig. 3a and Fig. 3b show an insulator part 2, 2c of a porcelain hollow insulator 2c, which is equipped on the inner side 21 with the field control layer 9, 9i. Optionally, in addition on the outside 23, a field control material coating 9o, z. B. in disjoint horizontal Strip 9o, preferably between insulator screens 2c and in particular in the lower Erdflanschbereich 7a, be present. Overall, therefore, the field control material 9; 9a, 9b; 9i, 9o be present in a coating or solid shape on an inner side 21 and / or integrated in an intermediate layer 22 between components 2a, 2b of the insulator part 2; 2a, 2b and / or on an outer side 23 of the insulator part 2; 2a, 2b; 2c is arranged.

According to Fig. 4 takes over the field control material 9; 9s a mechanically supporting function. Preferably, the field control material 9; 9s in the insulator part 2; 2b the exclusive mechanical self-supporting function, so that a conventional self-supporting plastic pipe 2a can be omitted. Such a field control material insulator tube 2; 2b including 9s is particularly simple in construction and very thin in diameter.

For DC applications, the field control element 9; 9i, 9s according to Fig. 2a . Fig. 3a and Fig. 4 on the insulator part 2; 2a, 2b; 2c over the entire surface and along a longitudinal extension x of the insulator part 2; 2a, 2b; 2c continuously and both with the first mounting flange 4; 8 as well as with the second mounting flange 8; 4 are in electrical contact.

A preferred choice of material for the field control materials 9; 9a, 9b; 9i, 9o; 9s comprises a matrix filled with microvaristor particles and / or high dielectric constant particles. Suitable microvaristor particles are, for example, doped ZnO particles, TiO ₂ particles or SnO ₂ particles. High dielectric constant have z. B. BaTiO ₃ particles or TiO ₂ particles. In the case of ZnO Mikrovaristorpartikeln these are typically sintered in a temperature range of 800 ° C to 1200 ° C. After rupture and optionally sieving of the sintered product, the microvaristor particles have a typical particle size of less than 125 μm. The matrix is chosen application-specific and can, for. Example, an epoxy, silicone, EPDM, thermoplastic, thermoplastic elastomer or glass. The filling of the matrix with microvaristor particles may be, for example, between 20% by volume and 60% by volume.

Fig. 5 12 shows calculations of the E field distribution E (x) normalized to a maximum E field E ₀ as a function of the longitudinal coordinate x of the insulator part 2 and the time represented by successive snapshots a, b, c for a conventional feedthrough 1 with shielding electrode 6 according to Fig. 1 and D, E, F, G for an inventive implementation 1 '. The calculations were made for a SF ₆ 170 kV bushing with GRP pipe 2a and silicone shield 2b according to conventional structure 1 or inventive construction 1 '. In Fig. 5 the electric field strength E (x) at the silicon - air interface is shown during or shortly after the application of a lightning impulse with time delays of 0.5 μs / 2.2 μs / 20 μs for the curves a, b, c and 0.5 μs / 1.0 μs / 5 μs / 20 μs for the curves D, E, F, G. It can be clearly seen that the new design of the bushing 1 'avoids the E-field peaks and at any time produces a more homogeneous electric field. Field distribution is achieved. In addition, the areas of increased field strength are no longer stationary, which has an advantageous effect on the dielectric behavior of the bushing 1 '. With the help of the field calculations and the nonlinear electrical and / or dielectric properties of the field control element 9; 9a, 9b; 9i, 9o; 9s, the field control design of the implementation 1 'can be optimized.

Fig. 6 shows an insufficient design, wherein the field control element 9; 9a, 9b; 9i, 9o; 9s has too high electrical conductivity or the length l; l ₁ , l _{2 is} too short. As a result, the E-field propagates along the field control layer 9; 9a, 9b; 9i, 9o; 9s, but is not degraded, so that at the end of the field control layer 9; 9a, 9b; 9i, 9o; 9s nevertheless again a field exaggeration occurs, the partial discharges, rollovers or punches. On the other hand, too low electrical conductivity of the field control material 9; 9a, 9b; 9i, 9o; 9s, the E-field can not be effectively controlled or controlled. For an optimal design of a varistor-like field control element 9; 9a; 9i, 9o; 9s in Erdflanschbereich 7, 7a, the simple but effective rule can be stated that the field control element length l; l ₁ , l _{2 is} greater than or equal to choose a ratio of a surge voltage to the critical electric field strength, the varistor switching behavior of the field control element 9; 9a, 9b; 9i, 9o; 9s characterized.

Uses of the inventive dielectric bushing 1 'relate inter alia to the use as a bushing 1' in a high-voltage electrical apparatus, in particular a disconnector, outdoor circuit breaker, vacuum switch, dead tank breaker, current transformer, voltage transformer, transformer, power capacitor or cable termination or in an electrical switchgear for high - or medium voltage. The invention also relates to a high-voltage electrical apparatus, in particular a disconnector, outdoor circuit breaker, dead tank breaker, current transformer, voltage transformer, transformer, power capacitor or cable termination, in which a dielectric feedthrough 1 'is present as described above. Likewise, an electrical switchgear, in particular a high or medium voltage switchgear comprising such a high voltage electrical apparatus claimed.

LIST OF REFERENCE NUMBERS

1

Conventional high voltage feedthrough

1'

FGM-high-voltage bushing

2

Self-supporting insulator

20

Isolation (solid, liquid, gel, gaseous), epoxy, foam, oil, air, SF ₆

21

Inside of the insulator part

22

Interlayer of the insulator part

23

Outside of the insulator part

2a

GRP pipe (glass fiber reinforced plastic), glass fiber reinforced epoxy pipe

2 B

External insulator, shielding, silicone shielding

2c

porcelain insulator

3

Conductor (at high voltage potential)

3a

central axis

3b

power connection

3c

power connection

4

Flange (grounded), ground flange

46

Contact between flange and shielding electrode

5

Housing of high voltage apparatus

6

shield

6a

Shielding electrode, earthing electrode

6b

Shielding electrode, high voltage electrode

7

Heavily field-polluted zone

7a

Field load zone in Erdflanschbereich

7b

Field loading zone in high voltage flange area

8th

Hochspannungsflansch

9

Field controlling material, FGM, varistor material, field controlling coating

9a

FGM in the earth flange area

9b

FGM in high voltage flange area

9i

FGM on insulator inner surface

9o

FGM on insulator outer surface

9s

self-supporting field-controlling insulator tube

a

conventional implementation, after 0.5 μs

b

conventional implementation, after 2.2 μs

c

conventional implementation, after 20 μs

D

FGM implementation, after 0.5 μs

e

FGM implementation, after 1.0 μs

F

FGM implementation, after 5 μs

G

FGM implementation, after 20 μs

d, d (l)

Thickness of field controlling coating or field controlling tube

d _i , d _o

Thickness of field controlling inner layer or outer layer

l

Length of field-controlling coating or field-controlling tube

l ₁ , l ₂

Length of the field-controlling coating in the Erdflanschbereich or Hochspannungsflanschbereich

Ex)

electric field distribution along high voltage feedthrough

E _o

maximum electric field, normalization field

x

Location coordinate along the longitudinal extent of the FGM implementation

Claims (13)

1. Dielectric bushing (1'), more particularly high-voltage bushing (1') for an electrical high-voltage apparatus, comprising an insulator part (2; 2a, 2b; 2c) having a first mounting flange (4) and a second mounting flange (8) for mounting the bushing (1'), characterized in that

   a) a screening electrode (6; 6a, 6b) required for a desired voltage level is omitted within the bushing (1') in a field loading zone (7; 7a, 7b) in the region of the first mounting flange (4; 8),

   b) instead, for the purpose of field control in the field loading zone (7; 7a, 7b), a non-linearly electrical and/or dielectric field control element (9; 9a, 9b; 9i, 9o; 9s) is present on the insulator part (2; 2a, 2b; 2c) in the region of the first mounting flange (4), and

   c) the field control element (9; 9a, 9b; 9i, 9o; 9s) is in electrical contact with the first mounting flange (4).
2. Bushing (1') according to Claim 1, characterized in that the field control element (9; 9a, 9b; 9i, 9o; 9s) is designed with regard to its non-linearly electrical and/or dielectric properties, its geometrical shape and its arrangement on the insulator part (2; 2a, 2b; 2c) for the dielectric load-relieving of the field loading zone (7; 7a, 7b) without a screening electrode (6; 6a, 6b) for all operating states, more particularly for surge voltages.
3. Bushing (1') according to either of the preceding claims, characterized in that the field control element (9; 9a, 9b; 9i, 9o; 9s) has:

   a) non-linearly electrical varistor properties and more particularly a critical field strength which characterizes a varistor switching behaviour of the field control element (9; 9a, 9b; 9i, 9o; 9s), and/or

   b) a high dielectric constant ε, more particularly ε > 30, preferably ε > 40 and particularly preferably ε > 50.
4. Bushing (1') according to any of the preceding claims, characterized in that the field control element (9; 9a, 9b; 9i, 9o; 9s) extends over a predeterminable length (l; l₁, l₂) along a longitudinal extent (x) of the insulator part (2; 2a, 2b; 2c) and has a predeterminable thickness (d) or thickness distribution (d(l)) as a function of the length (l; l₁, l₂).
5. Bushing (1') according to Claim 3, feature a), and Claim 4, characterized in that the length (l; l₁, l₂) is chosen to be greater than or equal to a ratio of a maximum surge voltage to be tested to the critical electric field strength.
6. Bushing (1') according to Claim 3, feature a), or Claim 4, dependent on Claim 3, feature a) , characterized in that the field control element (9; 9i, 9s), for DC applications, is present over the whole area on the insulator part (2; 2a, 2b; 2c) and continuously along a longitudinal extent (x) of the insulator part (2; 2a, 2b; 2c) and is in electrical contact both with the first mounting flange (4) and with the second mounting flange (8).
7. Bushing (1') according to any of the preceding claims, characterized in that

   a) the first mounting flange (4) is an earth-side mounting flange (4) for mounting the bushing (1') on an earthed housing (5) of an electrical apparatus, and/or

   b) the second mounting flange (8) is a voltage-side mounting flange (8) for mounting the bushing (1') on a high-voltage part, and/or

   c) the insulator part (2; 2a, 2b; 2c) has in the interior an insulation space for a solid insulation material (20) or for an insulation liquid (20) or a gas space for an insulation gas (20).
8. Bushing (1') according to Claim 7, feature a), and Claim 7, feature b), characterized in that

   a) a further field control element (9; 9b) is present, which has suitable non-linearly electrical and/or dielectric properties, more particularly those according to Claim 3, and is arranged in a field loading zone (7; 7a, 7b) in the region of the second mounting flange (8) over a predeterminable length (l; l₂) and thickness (d, d(l₂)) on the insulator part (2; 2a, 2b; 2c), and

   b) more particularly in that the further field control element (9; 9b) serves as a replacement for a screening electrode (6b) in the region of the second mounting flange (8).
9. Bushing (1') according to Claim 8, characterized in that

   a) the further field control element (9; 9b) is in electrical contact with the second mounting flange (8; 4), and/or

   b) the further field control element (9; 9b) is separated from the field control element (9; 9a; 9i, 9o) in the region of the first mounting flange (4) by a field-control-material-free zone extending along the longitudinal extent of the insulator part (2; 2a, 2b).
10. Bushing (1') according to any of the preceding claims, characterized in that

    a) the field control element (9; 9a, 9b; 9i, 9o; 9s) is present in a coating or solid configuration which is present on an inner side (21) and/or in an intermediate layer (22) in an integrated fashion between components (2a, 2b) of the insulator part (2; 2a, 2b) and/or on an outer side (23), more particularly there in disjoint horizontal strips (9o), of the insulator part (2; 2a, 2b; 2c), and/or

    b) the field control element (9; 9a, 9b; 9i, 9o; 9s) performs a mechanically supporting function, and more particularly in that the field control material (9; 9a, 9b; 9i, 9o; 9s) performs the exclusive mechanically self-supporting function in the insulator part (2; 2a, 2b; 2c).
11. Bushing (1') according to any of the preceding claims, characterized in that the field control element (9; 9a, 9b; 9i, 9o; 9s) comprises a matrix, more particularly an epoxy, silicone, EPDM, thermoplastic, thermoplastic elastomer or glass, and the matrix is filled

    a) with microvaristor particles, more particularly doped ZnO particles, TiO₂ particles or SnO₂ particles, and/or

    b) with particles having a high dielectric constant, more particularly with BaTiO₃ particles or TiO₂ particles.
12. Electrical high-voltage apparatus, more particularly disconnector, outdoor circuit-breaker, vacuum interrupter, dead tank breaker, current converter, voltage converter, transformer, power capacitor or cable end seal, characterized in that a dielectric bushing (1') according to any of the preceding claims is present.
13. Electrical switchgear assembly, more particularly high- or medium-voltage switchgear assembly, characterized by an electrical high-voltage apparatus according to Claim 12.

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