WO2013030389A1

WO2013030389A1 - Insulator for high-voltage gas insulated switch gear

Info

Publication number: WO2013030389A1
Application number: PCT/EP2012/067043
Authority: WO
Inventors: Nikolaus Zant; Dariusz Bednarowski; Robert Platek; Harald Martini; Andrzej RYBAK; Adam Michalik; Lukasz Malinowski
Original assignee: Abb Research Ltd; Abb Technology Ag
Priority date: 2011-09-02
Filing date: 2012-09-02
Publication date: 2013-03-07
Also published as: CN103765711A; EP2751892A1

Abstract

The invention is directed to an insulator (1) for a gas insulated device. The insulator comprises an injection molded insulator disc (2) and a conductor (3). The insulator disc (2) is made by injection molding of a first material. The insulator disc (2) comprises a center opening (4) encompassed by an inner bead (5) inside which the conductor (3) is arranged. A gap (18) arranged between the inner bead (5) and the conductor (3) is at least partially filled with a second material to form a transition means (19) between the insulator disc (2) and the conductor (3).

Description

INSULATOR FOR HIGH-VOLTAGE GAS INSULATED SWITCH GEAR

FIELD OF THE INVENTION

Aspects of the invention relate to an insulator for a gas insulated device, in particular to an insulator comprising an insulator disc surrounding a high voltage conductor. Further aspects relate to a gas insulated device comprising such an insulator. Further aspects relate to methods of producing such an insulator.

BACKGROUND OF THE INVENTION

A gas-insulated switchgear (GIS) accommodates high-voltage conductors such as lead conductors to which a high voltage is applied. In order to shield and insulate the high-voltage conductor from other components and from the outside, such an apparatus comprises a grounded metal enclosure filled with an insulating gas, generally a dielectric gas such as SF6.

In order to hold a high-voltage conductor firmly inside the device volume, in a position sufficiently far away from the grounded enclosure such as to avoid dielectric breakdowns, an insulator is provided inside the GIS enclosure. The insulator is secured at its outer edge to the enclosure, and has a central opening for accommodating the high-voltage conductor. The main portion of the spacer is an insulator disc, with the opening at its center. Some spacers may have a metal armature ring attached to the outer circumference of the insulator disc. The ar- mature ring may have attachment means such as thread holes, which allow the insulator disc to be firmly attached to the GIS enclosure.

For a long time for the manufacturing of insulators in GIS alumina filled epoxy has been used as basic material. Epoxy is a material which has good electrical insulating properties and mechanical strength but has also disadvantages. Epoxy is not environment-friendly and the manufacturing process (moulding) is complicated, time consuming, and therefore also relatively costly. An additional disadvantage of the epoxy insulators is the material inherit brittleness. This brit- tleness may lead to an unwanted sudden failure if loaded too high and therefore needs to be controlled closely to ensure proper part function. The manufacturing process is complex but a stable production critical for good part quality.

EP2273641 was filed in the name of ABB Technology AG and published in January 2011. It discloses a spacer for a gas insulated device. The spacer comprises an insulator disc and an armature extending around an outer periphery of the insulator disc and is foreseen to hold the insulator disc. For producing the spacer, an armature is positioned in a first molding cavity of a molding machine such that a second molding cavity is formed. An insulation material is brought into the second cavity and then cured such that the armature holds the insulator disc therein thus forming the insulator. The armature ring of an insulator may have a through channel (see [0056] and Fig. 13) extending across the ring in a radial direction and used for casting the mold.

JP2006340557A was filed in the name of Mitsubishi Electric Corp. and published in December 2006. It is directed to a disc-like member composed of an injection molded insulator. The leakage of insulating gas is blocked by an O-ring fitted in an annular groove. The O-ring can be prevented from falling, when the instrument is assembled in that it is fitted in an annular groove formed around the central axis of the disc-like member.

JP2004104897A was filed in the name of Fuji Electronic Holding Ltd. and is directed to the production of a spacer for a gas-insulated electrical apparatus using thermoplastic resin which can be easily recycled. An insulation body of the spacer is divided into a plurality of layers in the axial direction of a conductor. Each of the layers is formed using a thermoplastic resin and the divided bodies are integrally combined. By dividing an insulation body the thickness of each of the divided bodies can be reduced, thus enabling injection molding by the thermoplastic resin of each of the divided bodies. The layers are combined so as to be in a hollow shell condition, and partially or totally jointed by adhesion, fitting, or fusing, thus obtaining required mechanical strength and insulation strength. One drawback of this solution is that the insulator tends to comprise inclusions which are taking influence on the electrical field. A further drawback is the difficulty in the production of the product.

US4458100 was assigned to Westinghouse Electric Corp. and published in 1984. It is directed to a gas insulated transmission line having an insulator for supporting an inner conductor concentrically within an outer sheath. A common insulator is used for supporting the inner high voltage conductor within the outer conductor. A material, such as epoxy, is selected, which has a coefficient of expansion similar to the metal selected for the inner conductor so as to minimize the possibility of voids being formed at the critical interface where the insulator meets the conductor.

US4263476 was assigned to Electric Power Research Institute and published in 1979. It is directed to an injection molded insulator with a single insulator structure which is used in an elongated flexible gas-insulated cable. The insulator is made of two halves which are latched together and are made of any suitable plastic material by an injection molding process. It is described that the insulator would preferably be used in a flexible gas-insulated cable for a high voltage transmission system having a relatively low frequency (60 Hertz) at high voltage (345Ό00 volts). The central conductor of the cable is supported by the insulator within an outer corrugated housing. The housing is filled with an electronegative gas, such as SF6 at a positive pressure, for example, two to three atmospheres.

EP2062268 was filed in the name of Areva SA. and was published in March 2008. It is directed to an insulating support for a high-voltage or medium- voltage device. The insulating support is based on an insulating polymeric material comprising at least at one of its ends a zone, comprising a composite material, comprising a matrix made of an insulating polymeric material with an electrically conducting filler, which is a polymeric filler possibly encapsulating a mineral filler.

US7795541B was assigned to Areva AG. It was first published in 2006 and relates to an insulating device for medium or high voltage electrical equipment in the shape of a disc inside an enclosure acting as a support for an electrical conductor. The disc is made of thermoplastic polyester. The disc can be worked starting from a thick board using conventional machining tools and it can be provided with particular arrangements, for example to facilitate its assembly or connection of conductors supported on it. SUMMARY OF THE INVENTION

The present invention is directed to an insulator for electrical insulation, e.g. in switchgear such as a gas insulated device, wherein the insulator comprises an injection molded insulator disc and a conductor. The insulator disc comprises a center opening encompassed by an inner bead inside which the conductor is arranged. A gap arranged between the inner bead and the conductor is at least partially filled with a second material to form a transition means between the insulator disc and the conductor.

The insulator is made out of a thermoplastic material, which overcomes the disadvantages inherent to the prior art. The thermoplastic material preferably used is of ductile nature and therefore more fail safe. At least an insulator disc is produced by injection molding, which provides the following advantages: reduced cycle time, increased degree of automation and less complicated material preparation. However, the wall thickness may be limited, e.g. less than 10mm. The insulator disc may comprise structural components, such as ribs or other reinforcement means to increase stiffness and durability. The electrode can be over molded or assembled from two parts screwed together. If required the insulator disc may be built-up by a multi-stage injection molding process where structural parts and/or different materials are integrally combined to form the insulator disc or part of it.

In a preferred embodiment the insulator according to the invention comprises an injection molded insulator disc and a conductor, whereby the insulator disc is made by injection molding of a first material. The term 'first material' shall not be understood narrow in that it consists of one single material such as PET, for example, but broad in that it may be a material composition. However, a more detailed explanation will follow in this disclosure. The insulator disc comprises a center opening encompassed by an inner bead inside which the conductor is arranged. In a preferred embodiment an outer bead encompasses the insulator disc. If appropriate, the outer bead can be avoided. A gap is formed between the inner bead and the conductor. A first diameter of the center opening is at least partially larger then a second outer diameter of the conductor. The gap is at least partially filled with a second material to form a transition means between the insulator disc and the conductor. In an embodiment the conductor is at least initially positioned with respect to the insulator disc by at least one holding means. This provides the advantage of a precise alignment between the involved parts. The holding means can be provided e.g. by a circumferential holding rib or holding ribs extending in axial direction (axial holding rib) which are arranged such that the conductor can be properly aligned (centered) with respect to the insulator disc. The holding means can be formed as a separate part or forming an integral part of the insulator disc. The holding means can have at least one lateral opening to engage with (form fit) with the second material.

The conductor may comprise at least one first distribution channel for injection of the first material to form the insulator disc. The insulator disc may comprise a thin area which forms a nozzle which supports the uniform distribution of the material, while making the insulator disc. The nozzle is preferably arranged between the first distribution channel and the inner bead. The nozzle can later form part of the holding means. The nozzle may at least partially be arranged inside the conductor. On the inside of the nozzle a circumferential channel may be arranged for distribution of the first material in a circumferential direction during making the insulator disc. The conductor may comprise at least one se- cond distribution channel arranged within the conductor by which a second material for forming of the transition means is injected. Alternatively or in addition, the second material for forming of the transition means is inserted into the axial gap e.g. by a robot. The transition means may be form fit to the insulator disc and/or the conductor.

In an embodiment the inner and/or the outer bead is strut by a plurality of reinforcement ribs arranged on at least one of a first and a second side surface forming a reinforcement rib structure. The reinforcement rib structure may comprise several radial and/or at least one circumferential reinforcement rib (middle bead) arranged between the inner and the outer bead. The reinforcement rib structure may also comprise a comb-like arrangement of reinforcement ribs. In general, the thickness of the reinforcement ribs varies with respect to the thickness of the wall of the insulator disc by a maximum of 20%. The reinforcement ribs may have an evenly distributed setup with respect to the center opening. The reinforcement ribs may have a curved shape or be arranged at an angle with respect to a centre axis of the conductor. The insulator disc may have a conical shape. If appropriate, the insulator may comprise at least one cross- port which e.g. extends between two reinforcement ribs in an axial direction. The at least one cross-port serves to exchange insulator gas between several sections of the gas insulated device. The reinforcement ribs may interconnect the inner and the outer bead directly or indirectly. For reducing the local wall thickness, the reinforcement ribs may be arranged alternatively with respect to the wall of the insulator disc.

Depending on the field of application, the insulator disc may be encompassed by a flange made out of a conductive material. If appropriate, the insulator may comprise at least one field control element, which is at least partially embedded in the insulator disc. Normally the at least one field control element is electrically interconnected to the conductor or the flange by a connecting element.

If appropriate, at least one seal is attached to the insulator disc. The at least one seal may be joint to the insulator disc by injection molding of the at least one seal onto the insulator disc. The transition means may comprise a conductive material.

A method for the production of an insulator comprises the following method steps:

(a) Providing a mold for injection molding of an insulator disc the insulator disc comprising an inner bead encompassing a center opening;

(b) Arranging inside the center opening a conductor whereby the conductor is distanced by a gap from the inner bead;

(c) Introducing a second material into the gap to form a transition means between the inner bead and the conductor.

If appropriate the first material is injected through at least one channel arranged inside the conductor. The second material may be injected through a channel arranged inside the conductor and/or by direct injection into the gap. The conductor may be preheated to a defined temperature before step before injection of the first material. For this reason the mold may comprise appropriate means, e.g. in the form of appropriate connection channels, to interconnect to at least one of the channels arranged in the conductor. Alternatively or in addition the mold can be designed such that the conductor is directly accessible form the outside, i.e. the mold comprises an opening through which the conductor, respectively the channels arranged in the conductor, are accessible from the out- side when the conductor is arranged inside of the closed mold. The mold may comprise an adapter to receive and temporarily hold the conductor during the injection molding process. The adapter may be designed exchangeable such that different conductors can be processed with the same mold. If appropriate the adapter can be part of the cavity of the mold thereby being at least partially in contact with the injection molded material.

A mold for making of an insulator disc in general comprises: a first mold half, a second mold half interacting with the first mold half along a parting plane, at least one cavity corresponding to an insulator disc encompassed by the first and the second mold half. The mold may further comprise at least one adapter suitable to receive and temporarily hold a conductor during injection molding of the insulator disc, at least one injection nozzle arranged at the first mold half discharging directly or indirectly into the at least one cavity. Depending on the field of application and the design of the insulator it is possible to use at least two different injection nozzles to inject the material. The injection mold may comprise at least one adapter which may form part of one of the mold halves. The at least one adapter may have an in general cylindrical shape. The at least one adapter may comprise clamping means to temporarily receive and hold the conductor. The at least one adapter may be arranged displaceable independent of a movement of the mold halves. The at least one adapter may be arranged displaceable against the force of a spring. If the insulator disc shall be produced independent of the conductor it is possible to use a dummy which is later replaced by the conductor. The dummy is placed in the mold instead of the adapter. If required the area forming the inside of the insulator disc can be completely integrated in the mold. The injection mold may comprise at least one ejector. The ejector is preferably arranged at the second mold half to eject the insulator from the injection mold. The at least one ejector may be arranged in the region of and acting upon the outer rim of the insulator disc. Alternatively or in addition the at least one ejector may be arranged in the region of and acting upon conductor of the insulator disc. Further ejectors may be arranged in- between.

The at least one injection nozzle may discharge into the cavity in the area of the outer rim of insulator disc. Furthermore, alternatively or in addition the at least one injection nozzle may discharge into the cavity through at least one channel arranged in the conductor and/or another mold part. Alternatively or in addition the at least one injection nozzle may discharge into the cavity through at least one gap designed to act as a film gate. The at least one gap may be interconnected to a chamber into which the material is discharged first. The at least one gap may have a variable geometry in circumferential direction and/or have several segments.

In a preferred embodiment, the material is injected by at least one first distribution channel arranged at a circumferential position with respect to the insulator disc. The distribution channel at least partially encompasses the insulator disc. If appropriate, the distribution channel may be separated in segments.

A method for making of an insulator disc as described above in general comprises the following method steps: a. providing an injection mold having: i. a first mold half; ii. a second mold half interacting with the first mold half along a parting plane; iii. a cavity corresponding to the insulator encompassed by the first and the second mold half; iv. at least one injection nozzle arranged at the first mold half suitable to discharge liquefied material into the cavity directly or indirectly; b. closing the mold by relative movement of the first with respect to the second mold half until the cavity is closed; c. injecting liquefied material through the at least one injection nozzle; d. opening the mold by relative movement of the first with respect to the second mold half (16, 17); and e. removing the insulator from the mold cavity (17).

If required it is possible to provide in the mold at least one adapter suitable to receive and temporarily hold a conductor during injection molding of the insulator disc. In this case, before injecting the liquefied material into the cavity, the mold is opened by relative movement of the first mold half with respect to the second mold half in a first direction. Then a conductor is attached to the at least one adapter and the mold is subsequently closed.

At least one part of the mold may be arranged movable to reduce the volume of the cavity and thereby compressing the material in the cavity after and/or during injection of the liquefied material. By this compression step the quality of the surface of the insulator disc can be improved. The compression step can be performed by relative movement of the mold halves from a first into a second closing position. Alternatively or in addition at least one segment of at least one of the mold halves can be designed movable independent of the movement of the mold halves. E. g. a ring like segment in the area of the outer bead can be arranged moveable for the compression step. Thereby it is possible to avoid parting lines in the functional critical area of the insulator disc.

The injection compression molding process can further increase the advantages of the injection molding process, especially help to reduce residual stress in the part through the evenly distributed pressure throughout the mold cavity during the compression step. This favorable pressure distribution will also lead to a superior surface quality - when used in combination with a mirror polished mold cavity surface. A further advantage of an insulator surface having a surface roughness that is as low as possible resides in that the electric field is locally less intensified at the insulator surface compared to an insulator surface having a higher roughness. Hereinafter, the term surface roughness is to be understood as the surface quality, i.e. the amount of the vertical deviations of a real surface from its ideal form. These deviations relate to the size and the number of peaks/valleys on the surface of a body in general. If these deviations are large, the surface is rough; if they are small the surface is smooth. The lower the surface roughness value is, the lower locally intensified the electric fields are once the insulator disc is in an operating state of the high voltage gas insulated device. This explanations relating to the effects and advantages arising of the injection compression molding is not limited to this particular embodiment and applies likewise to all remaining embodiments disclosed in the present application.

If appropriate the at least one ejector is activated to eject the insulator from the injection mold. The several injection nozzles may be arranged in at least one concentric row or at least one group around the center of the mold. The several injection nozzles may be activated simultaneously or in a sequence, e.g. in that at least two injection nozzles are activated at different times to obtain uniform material distribution. An outer surface of the conductor may be treated by a surface treatment and/or coated by a coating material to increase bonding of the material injection molded onto the outer surface.

In an embodiment the first material is at least one out of the group of the following materials: polyesters (e.g. polyethylene terephthalate, polybutylene ter- ephthalate), polyamide (PA), polysulfone (e.g. PES), polyetherimide (PEI), poly- phenylene sulfide (PPS), polyether ether ketone (PEEK ), polyphthalamide (PPA), polypropylene (PP), polyoxymethylene (POM), phenol formaldehyd (PF), unsatured polyester (UP), polyurethane (PUR and PU). The first material may comprise at least one filler material out of the group of the following filler materials: Polyamide, polyimide, polyester, polyvinyl alcohol, polyvinylidene chloride, pol- yacrylonitrile, polyurethane, polyalkylene paraoxybenzoate, phenol type, wool, silk, cotton, rayon, cellulose acetate, flax, ramie, jute, aramid fibres, glass, sepio- lite, potassium titanate, ceramic, alumina, calcium silicate, rock wool. The second material may be at least one out of the following material groups: thermoplastic elastomers (TPE), thermoplastic polyurethanes (TPU), epoxies or polyurethane (PUR or PU). A third material may be filled in a space delimited by at least two ribs. Alternatively or in addition, the third material can be used to coat the side surface (wall) of the insulator disc and/or the ribs. Said third material may be at least one out of the group of: thermoplastic elastomers (TPE), thermoplastic polyurethanes (TPU), polyurethane (PUR or PU) or Silicones. For economic manufacturing of the insulator the first material is preferably at least one out of the group of the following materials: a polyester (e.g. ΡΕΤ,ΡΒΤ), a polyamide (PA), a polyphtalamide (PPA), a polypropylene (PP), a polyoxymethylene (POM), phenol formaldehyd (PF), unsatured polyester (UP) or polyurethane (PUR and PU). For high thermal stability at least one out of the group of the following polymers is preferred: polysulfone (e.g. PES), polyetherimide (PEI), polyphenylene sulfide (PPS) or a polyether ether ketone (PEEK ).

BRIEF DESCRIPTION OF THE DRAWINGS

The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

Fig. 1 a first embodiment of an insulator in a perspective view; Fig. 2 the first embodiment in a front view;

Fig. 3 a section view of the first embodiment along section line 3-3 according to Fig 2;

Fig. 4 a second embodiment of the insulator in a perspective view; Fig. 5 the second embodiment in a front view;

Fig. 6 a section view of the second embodiment along section line 6-6 according to Fig. 5;

Fig. 7 a third embodiment of the insulator in a perspective view partially cut;

Fig. 8 the third embodiment according to Fig. 7 with a second material component;

Fig. 9 a fourth embodiment of the insulator in a perspective view; Fig. 10 the fourth embodiment in a front view; Fig. 11 a section view of the fourth embodiment along section line 11-11 according to Fig. 10;

Fig. 12 a fifth embodiment of the insulator in a perspective view;

Fig. 13 the fifth embodiment in a front view;

Fig. 14 a section view of the fifth embodiment along section line 14-14 according to Fig. 13;

Fig. 15 a sixth embodiment of the insulator in a perspective view;

Fig. 16 the sixth embodiment in a front view;

Fig. 17 a section view of the sixth embodiment along section line 17-17 according to Fig. 16;

Fig. 18 a seventh embodiment of the insulator in a perspective view;

Fig. 19 the seventh embodiment in a front view;

Fig. 20 a section view of the seventh embodiment along section line 20-20 according to Fig. 19.

DESCRIPTION OF THE EMBODIMENTS

The foregoing summary as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there are shown in the drawings several embodiments in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.

Figure 1 shows a first embodiment of an insulator 1 according to the present invention in a perspective view. Figure 2 shows the insulator according to Fig- ure 1 in a front view and Figure 3 shows the insulator 1 in section view along section line 3-3 according to Figure 2.

Figure 4 shows a second embodiment of an insulator 1 according to the present invention in a perspective view. Figure 5 shows the insulator according to Figure 4 in a front view and Figure 6 shows the insulator 1 in section view along section line 6-6 according to Figure 5.

Figure 7 shows a third embodiment of an insulator 1 according to the present invention in a perspective view and in partially cut manner such that the inside of the insulator 1 becomes visible. Figure 8 shows the insulator according to Figure 7 and comprising a second material component as will be described in more detail subsequent.

Figure 9 shows a fourth embodiment of an insulator 1 according to the present invention in a perspective view. Figure 10 shows the insulator according to Figure 9 in a front view and Figure 11 shows the insulator 1 in section view along section line 11-11 according to Figure 10. Figure 12 shows a fifth embodiment of an insulator disc 2 according to the present invention in a perspective view. Figure 13 shows the insulator disc 2 according to Figure 12 in a front view and Figure 14 shows the insulator disc 2 in section view along section line 14-14 according to Figure 13. Figure 15 shows a sixth embodiment of an insulator disc 2 according to the present invention in a perspective view. Figure 16 shows the insulator disc 2 according to Figure 15 in a front view and Figure 17 shows the insulator disc 2 in section view along section line 17-17 according to Figure 16.

Figure 18 shows a seventh embodiment of an insulator disc 2 according to the present invention in a perspective view. Figure 19 shows the insulator disc 2 according to Figure 18 in a front view and Figure 20 shows the insulator disc 2 in section view along section line 20-20 according to Figure 19.

The insulator 1 according to the present invention in general comprises a conductor 3, which is arranged in a center opening 4 of an insulator disc 2. If appropriate, the insulator disc 2 comprises an inner bead 5 and an outer bead 6, which delimit the insulator disc 2 with respect to the inside and to the outside. The inner and/or the outer bead 5, 6 may be strut by radial reinforcement ribs 7 to increase the mechanical stability of the insulator disc 2. The radial reinforcement ribs 7 can be arranged protruding on at least one side above a wall 14.

The insulator discs 2 of the shown embodiments are made by injection molding of a first material. The injection molding process can be performed in one or several steps whereby the conductor 3 may be placed inside of a mold (not shown in detail) for the injection molding process of the insulator disc 2. The mold preferably comprises an adapter which is foreseen to receive and hold a conductor during the injection molding process. The adapter can be designed exchangeable such that different conductors can be processed with the same mold or the same adapter can be used in different molds for the production of different insulator discs 2. For injection molding of the at least one material the mold may comprise appropriate means, e.g. in the form of appropriate connection channels, to interconnect to at least one of the channels arranged in the conductor. Alternatively or in addition the mold can be designed such that the conductor is directly accessible form the outside, i.e. the mold comprises an opening through which the conductor, respectively the channels arranged in the conductor, are accessible from the outside when the conductor is arranged inside of the closed mold.

In another embodiment insulator disc 2 is made first and the conductor is mounted inside the opening 4 after the insulator disc 2 has been made. In certain embodiments the conductor 3 and the insulator disc 2 are at least partially spaced apart by a gap 18, which is at least partially filled with a second material to form a transition means 19.

If appropriate the interacting surface of the conductor 3 and/or the insulator disc 2 can be coated by an appropriate material and/or undertaken a surface treatment to increase the bonding process.

The first embodiment of the insulator 1 as shown in the Figures 1 through 3 comprises an insulator disc 2 with an inner bead 5 and an outer bead 6. The inner bead 5 surrounds a center opening 4 in which a conductor 3 is arranged in a coaxial manner. Between the conductor 3 and the inner bead 5 a gap 18 extends in a vertical direction (z-axis). The gap 18 is filled by a second material forming a transition means 19, which interconnects the insulator disc 2 and the inner conductor. As it can be seen in the section view according to Figure 3, the conductor comprises teeth 26 which form fit with the transition means 19. The term 'teeth' shall not be understood as a jagged structure in a narrow sense since sharp edges shall be avoided for dielectric reasons. The term 'teeth' shall be rather understood in a broad sense as a representative term for any suitable locking means for establishing a form fit by a variation in diameter relative to the center axis of the insulator. That engaging means blocks the insulator body with the transition means 19 from being stripped off the conductor in an axial direction easily, i.e. in the direction of the center axis of the insulator. Moreover, the locking means serves for increasing an overall contact surface in between the conductor and the insulator disc or the conductor and the transition means 19 respectively.

The opening 4 formed by the bead 5 has a conical shape, whereby the smallest diameter is in the middle with respect to the vertical direction and increases versus both ends. The second material is filled in the gap e.g. by a robot or another appropriate device. If appropriate, the inside of the surfaces of the conductor 3 and/or the insulator disc 2 being in contact with the second material can be coated with a coating material to improve the adhesion. In this embodiment the inner and the outer bead 5, 6 are strut by radial reinforcement ribs 7, which are evenly distributed in circumferential direction. As it can be seen in Figure 3, the radial reinforcement ribs 7 have a conical shape with a thickness which is decreasing in radial direction. The radial reinforcement ribs 7 are arranged perpendicular to a center axis a. If appropriate, the ribs 7 can be arranged at an angle (i.e. in a skew manner) with respect to the center axis a. Between the radial reinforcement ribs 7 a wall 14 is arranged in circumferential direction. If required, the wall 14 can be omitted and being replaced by an opening (cross port) 15. The cross port 15 prevent that the two adjacent sections of the gas insulated device are hermetically sealed with respect to each other. If required, the space between two reinforcement ribs can be at least partially filled with a third material 25 (schematically indicated by hatched area) as mentioned above. If required, the complete side surface or only specific parts of it can be covered by the third material.

For making of an insulator 1 the following steps are normally executed: a. Providing a mold for injection molding of an insulator disc 2 the insulator disc 2 comprising an inner bead 5 encompassing a center opening 4; b. arranging inside the center opening 4 an conductor 3, whereby the conductor 3 is distanced by a gap 18 from the inner bead 5; c. introducing a second material into the gap 18 to form a transition means between 19 the inner bead 5 and the conductor 3.

The second embodiment of the insulator 1 as shown in the Figures 4 through 6 corresponds in general to the first embodiment as mentioned above. The second embodiment comprises an insulator disc 2 which is in direct contact with the conductor 3 by a holding means in the form of holding ribs 16 arranged in axial direction (z-direction). The holding ribs 16 are designed to position and hold the conductor 3 with respect to the insulator disc 2 at least until the second material is applied into the gap 18 to form the transition means 19. The holding ribs guarantee a precise alignment of the conductor with respect to the insulator disc 2. The holding ribs 16 are arranged evenly distributed in circumferential direction. As it can be seen in Figures 5 and 6, in difference to the first embodiment, the reinforcement ribs 7 of this second embodiment are arranged in circumferential direction alternatively with respect to the wall 14.

The conductor 3 in the embodiment according to Figures 4 through 6 is used to inject the first material to form the insulator disc 2 at least partially. The conductor 3 therefore comprises first distribution channels 10.1 to which an injection nozzle (not shown in detail) can be connected for injecting the first material to form the insulator disc 2 as described below. As it can be seen in Figure 5, the distribution channels 10.1 have a star-like arrangement and are aligned to the axial holding ribs 16 through which the material injection takes place during the manufacturing step. This may support the uniform distribution of the material during the injection molding process. For manufacturing of the insulator disc 2 the conductor 3 is positioned in a mold (not shown in detail), which is normally at least partially a negative of the final insulator disc 2 to be made, then the mold is closed and first material is injected in liquid form into the distribution channels 10.1 until the mold to form the insulator disc 2 is sufficiently filled. The first material enters into the mold through the holding ribs 16. Before the first material is injected, the conductor 3 can be heated until a certain temperature is achieved. This can improve the results of the injection molding process. After the material has cured, the mold is opened and the conductor 3 and the insulator disc 2 are removed. If appropriate, the insulator disc 2 can be made in multistage injection molding process, whereby the insulator disc 2 is build up in several stages. As visible in Figures 5 and 6, the conductor 3 may be equipped with second distribution channels 10.2, which can be used to inject the second material in the gap 18 to form the transition means 19.

The first and/or the second distribution channels 10.1, 10.2 can be avoided and the insulator disc and/or the transition means can be made by a conventional injection molding process, whereby the first material and/or the second material are not injected through the conductor 3. E.g. after the insulator disc 2 has been made, the conductor 3 is placed in the center opening 4 of the insulator disc 2, wherein it is held and positioned by the axial holding ribs 16 in a precise manner. Then the second material is e.g. filled through the second distribution channels into the gap 18 to form the transition means 19. Alternatively or in addition, the second material is directly filled in the gap 18 to form the transition means 19. In the center opening 4 of the third embodiment according to Figures 7 and 8 a holding means in the form of a circumferential holding rib 17 is visible, which on the inner end merges into a thickening 11 inside which the conductor 3 can be positioned and held as shown in Figure 7. In axial direction above and below the circumferential holding rib 17, the gap 18 extends, which is filled by the second material as shown in Figure 8 to form the transition means 19. The holding means may comprise at least one lateral 20.

The conductor 3 can comprise first and/or second distribution channels to injection molding of plastic material in the sense of the second embodiment according to Figures 4 through 6. If first distribution channels are present, they are preferably interconnected to the thickening 11, which acts as a circumferential channel to distribute material in circumferential direction and to uniformly distribute the material through gap formed in the mold in the area of the circumferential rib 17, which acts as a nozzle to introduce and uniformly distribute the material in the insulator disc 2.

In the third embodiment according to Figures 7 and 8, the insulator disc 2 is encompassed by an outer ring 22 made out of a conductive material. Examples for suitable materials are a ferromagnetic alloy or a polymer with a carbonaceous content. Two field control elements 21.1, 21.2 are embedded in the insulator disc 2. The inner field control element 21.1 is electrically interconnected by an inner connecting element 23.1 to the conductor 3. The outer field control element 21.2 is electrically interconnected by an outer connecting element 23.2 with the outer ring 22.

The fourth embodiment according to Figures 9 through 11 in general corresponds to the other embodiments mentioned above. As it can be seen in the section view according to Figure 11, the insulator disc 2 comprises a seal 24, which penetrates the insulator disc 2 through axial openings 28 in the insulator disc 2. The seal 24 is preferably made by an injection molding process. Therefore, the insulator disc 2 is placed in an injection mold and a third or a fourth material is injected to form the seal. In the shown embodiment the material for the seal may be injected through a radial opening 29 in the outer bead 6.

Figures 12 through 14 are showing a fifth embodiment of an insulator disc 2, suitable to be used in an insulator 1 according to the herein described invention. The insulator disc 2 has in general the same design as the foregoing insulator discs 2. Regarding the general explanations it is therefore referred to those. The insulator disc 2 is made by injection molding of a first material. It comprises radial and circumferential reinforcement ribs 7, 30. The circumferential reinforcement ribs 30 are arranged coaxial between the inner and the outer bead forming closed circles. Some of the radial reinforcement ribs 7 interconnect the inner and the outer bead 5, 6. Other radial reinforcement ribs 7 have a shorter design and extend in the outer region of the insulator disc 2 between the outer bead 6 and a circumferential reinforcement rib 30. The shown insulator disc is preferable for insulators having a relatively large diameter. As it can be seen, the radial and the circumferential reinforcement ribs 7, 30 all have the same thickness in axial direction, which is only reduced in the region of the outer bead 6. Between the reinforcement ribs 7, 30 a wall 14 extends, which prevents leaking. If required, at least one cross port (not shown in detail) can be foreseen for exchange of insulator gas as mentioned above.

Figures 15 through 17 are showing a sixth embodiment of an insulator disc 2 suitable to be used in an insulator 1 according to the herein described invention. The insulator disc 2 has in general the same design as the foregoing insulator discs 2. Regarding the general explanations it is therefore referred to those. The insulator disc 2 is made by injection molding of a first material. As it can be seen in Figure 17, the axial reinforcement ribs 7 have a wave-like cross-section. This offers the advantage that the side surfaces 8.1, 8.2 can easily be cleaned especially during assembly of the device. Furthermore, the reinforcement ribs 7 offer a high mechanical durability and a low material consumption. A further advantage is that the material during injection molding is equally distributed.

Figures 18 through 20 are showing a seventh embodiment of an insulator disc 2 suitable to be used in an insulator 1 according to the herein described invention. The insulator disc 2 has in general the same design as the foregoing insulator discs 2. Regarding the general explanations it is therefore referred to those. The insulator disc 2 is made by injection molding of a first material. The reinforcement ribs 7 have a comb-like design, which supports the distribution of the occurring forces.

LIST OF DESIGNATIONS a Centre Axis 13 Distribution opening

1 Insulator 14 Wall (between ribs)

2 Insulator disc 15 Cross port (opening)

3 Conductor 25 16 Axial holding rib (holding

4 Center opening means)

5 Inner bead 17 Circumferential holding rib

6 Outer bead (holding means) / Nozzle

7 Radial reinforcement rib 18 Gap

8 8.1: First Side surface (insu30 19 Transition means / Adhesive lator disc) material

8.2: Second Side surface (in20 Lateral opening

sulator disc) 21 21.1: Inner field control ele¬

9 Injection opening ment / conductor

10 10.1: First distribution chan35 21.2: Outer field control elnel ement / flange

10.2: Second distribution 22 Flange (outer ring) channel 23 23.1: Inner connecting ele¬

11 Thickening / Distribution ment (field control element chamber 40 / conductor)

12 Outer surface (conductor) 23.2: Outer connecting element (field control element Axial opening (insulator disc) / flange) 10 Radial opening (insulator Seal disc)

Filler (Material filled in beCircumferential reinforcetween ribs) ment rib

Teeth (Locking element)

Claims

PATENT CLAIMS

1. Insulator (1) for a gas insulated device, comprising an injection molded insulator disc (2) and a conductor (3), whereby the insulator disc (2) is made by injection molding of a first material, whereby the insulator disc (2) comprises a center opening (4) encompassed by an inner bead (5) inside which the conductor (3) is arranged and an outer bead (6) encompassing the insulator disc (2), and whereby a gap (18) arranged between the inner bead (5) and the conductor (3) is at least partially filled with a second material to form a transition means (19) between the insulator disc (2) and the conductor (3).

2. The insulator (1) according to claim 1, characterized in that the conductor (3) is positioned with respect to the insulator disc (2) by at least one holding means (17).

3. The insulator (1) according to claim 2, characterized in that the conductor (3) is arranged inside the holding means (17) in a form-fit manner.

4. The insulator (1) according to one of the previous claims, characterized in that the holding means is at least one from the following group of holding means: a circumferential rib (17), at least three axial ribs (16), a shoulder forming a mechanical stop for delimiting axial movement of the conductor with respect to the insulator body in one direction.

5. The insulator (1) according to one of the claims 2 to 4, characterized in that the holding means (17) is integrally connected to the insulator disc (2).

6. The insulator (1) according to one of the previous claims, characterized in that the conductor (3) comprises at least one first distribution channel (10.1) for injection of the first material to form the insulator disc (2).

7. The insulator (1) according to claim 6, characterized in that the insulator disc (2) comprises a bridge element (17) for uniform distribution of the material during injection molding of the insulator disc (2), whereby the bridge element (17) is arranged between the first distribution channel (10.1) and the inner bead (5).

8. The insulator (1) according to claim 7, characterized in that the bridge element (17) is arranged at least partially inside the conductor (3).

9. The insulator (1) according to claim 7 or 8, characterized in that on the inside of the bridge element (17) a circumferential channel (11) is arranged for distribution of material in a circumferential direction during injection molding of the insulator disc (2).

10. The insulator (1) according to one of the previous claims, characterized in that the conductor (3) comprises at least one second distribution channel (10.2) arranged within the conductor (3) by which a second material for forming a transition means (19) is injectable after injection molding of the insulator disc (2).

11. The insulator (1) according to one of the previous claims, characterized in that the transition means (19) is form fit to the insulator disc (2) and/or the conductor.

12. The insulator (1) according to one of the previous claims, characterized in that the inner bead (5) and/or the outer bead (6) is strut by a plurality of ribs (7) arranged on at least one of a first side surface (8.1) and a second side surface (8.2) such that a rib structure (7) is formed.

13. The insulator (1) according to claim 12, characterized in that a thickness of the ribs (7) differs from a thickness of the wall (14) by a maximum of 20%.

14. The insulator (1) according to claim 12 or 13, characterized in that the insulator disc (2) comprises at least at least one cross-port (15) extending in an axial direction (z) of the insulator (1) such that a first side surface (8.1) and a second side surface (8.2) are connected to one another.

15. The insulator (1) according to one of the claims 12 to 14, characterized in that the ribs (7) interconnect the inner bead (5) and the outer bead (6).

16. The insulator (1) according to one of the claims 12 to 15, characterized in that the ribs (7) on a first side surface (8.01) and on a second side surface (8.2) of the insulator disc (2) are arranged circumferentially displaced from one another such that the ribs (7) are arranged alternatively with respect to the wall (14) of the insulator disc (2) in a circumferential direction.

17. The insulator (1) according to one of the previous claims, characterized in that at least one field control element (21) is embedded in the insulator disc (2).

18. The insulator (1) according to claim to one of the previous claims, characterized in that at the at least one seal (24) is joint to the insulator disc (2) by injection molding of the at least one seal (24) onto the insulator disc (2).

19. The insulator (1) according to one of the previous claims, characterized in that the transition means (19) comprises an electrically conductive material for acting as a further field control element in an operating state of the insulator (1).

20. The insulator (1) according to one of the previous claims, characterized in that the first material comprises at least one material selected from the group of the following materials: PET, PBT, PA, PES, PEI, PPS, PEEK, PPA, PP, POM, PF (phenol formaldehyd resin), UP (unsatured Polyester), PUR.

21. The insulator (1) according to one of the previous claims, characterized in that the first material comprises at least one filler material selected from the group of the following filler materials: Polyamide, polyimide, polyester, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile, polyurethane, polyalkylene paraoxybenzoate, phenol type, wool, silk, cotton, rayon, cellulose acetate, flax, ramie, jute, aramid fibres, glass, sepiolite, potassium ti- tanate, ceramic, alumina, calcium silicate, rock wool.

22. The insulator (1) according to one of the previous claims, characterized in that the second material comprises at least one material selected from the group of the following materials: TPE, TPU, Epoxy, PUR.

23. The insulator (1) according to one of the previous claims, characterized in that a space delimited by at least two ribs is at least partially filled with a third material.

24. The insulator (1) according to one of the previous claims, characterized in that the insulator disc (2) is at least partially coated by a fourth material.

25. A medium voltage or high voltage switchgear comprising at least one insulator (1) according to any one of the previous claims.

26. The medium voltage or high voltage switchgear according to claim 25, characterized in that the medium voltage or high voltage switchgear is gas insulated such that an insulation gas is contacting the insulator disc (2) at least partially.

27. Method for the production of an insulator (1) according to one of the claims 1 to 24, said method comprising the following steps: a. Providing a mold for injection molding of an insulator disc (2), the insulator disc (2) comprising an inner bead (5) encompassing a center opening (4) and molding such an insulator disc (2); b. Arranging a conductor (3) inside the center opening (4) of the insulator disc (2), whereby the conductor (3) is distanced by a gap (18) from the inner bead (5); c. Introducing a second material into the gap (18) to form a transition means between (19) the inner bead (5) and the conductor (3).

Method according to claim 27, characterized in that the first material is injected through at least one channel (10.1) arranged inside the conductor (3).

29. Use of the insulator (1) according to any one of claims 1 to 24 in a medium voltage or high voltage switchgear.

30. Use according to claim 29, characterized in that the medium voltage or high voltage switchgear is gas insulated such that an insulation gas is contacting the insulator disc (2) at least partially.

31. Method for making of an insulator disc (1), said insulator disc comprising: a. an insulator disc (2) having a center opening (4) and an inner bead (5) and an outer bead (6); b. a conductor (3) arranged in the center opening (4) of the insulator disc; said method comprising the following method steps: c. providing an injection mold having: i. a first mold half; ii. a second mold half interacting with the first mold half along a parting plane (18); iii. a cavity corresponding to the insulator (1) encompassed by the first and the second mold half; iv. at least one injection nozzle arranged at the first mold half suitable to discharge liquefied material into the cavity directly or indirectly; d. closing the mold (1) by relative movement of the first with respect to the second mold half until the cavity is closed; e. injecting liquefied material through the at least one injection nozzle; f. opening the mold by relative movement of the first with respect to the second mold half; and g. removing the insulator (1) from the mold cavity.

32. The method according to claim 31, characterized in that providing in the mold at least one adapter suitable to receive and temporarily hold a conductor (3) during injection molding of the insulator disc and, before injecting liquefied material into the cavity, opening the mold by relative movement of the first mold half with respect to the second mold half in a first direction (z) and attaching a conductor (3) to the at least one adapter.

33. The method according to one of the claims 31 or 32, characterized in that at least one part of the mold is arranged movable to reduce the volume of the cavity and thereby compressing the material in the cavity after and/or during injection of the liquefied material.

The method according to one of the claims 31 to 33, characterized in that it is a method for the production of an insulator (1) according to one of claims 1 to 24.