EP2071592A1 - Corona shield and composite isolator with corona shield - Google Patents

Abstract

A plastic single-piece corona shield (2) is suitable for being fitted co-axially on a composite insulator on a crossover from a rod (3) to fittings (8a,8b) at the end. The corona shield forms a cavity (16a,16b) opened inwards that can be filled with a sealing compound (22) via a filling channel and has closing sleeves (17,18) in an axial direction on both sides for sealing the cavity. An independent claim is also included for a composite insulator.

Description

The present invention relates generally to the insulator technique, and more particularly to a corona shield made of insulating plastic, and to a composite insulator having at least one such corona shield.

High-voltage composite insulators usually have a mechanical load absorbing insulating rod (usually made of glass fiber reinforced hard plastic), about a jacket and ribs of insulating plastic (usually a plastic with hydrophobic and dirt-repellent surface, such as silicone rubber), and firmly connected to the rod and as fastening devices Serving end fittings (usually made of metal) on.

Often it comes with a high voltage insulator under voltage to corona discharges. Such a corona discharge can erode effect on the insulating jacket. Namely, it can attack the surface of the insulating jacket, especially in the vicinity of the end fittings (because of the field strength that is particularly high there), thereby shortening the life of the insulator.

A common countermeasure is to use the so-called, often attached to the end fitting corona rings of conductive material (usually metal) or semiconducting material (usually mixed with conductive particles plastic) to form the electric field at the end fitting so that the field strength is reduced. This reduces the tendency for corona discharge, or at least the concentration of corona discharge on the surface of the insulating jacket near the end fitting.

Alternatively, the document describes US 6,984,790 B1 a corona shield made of metal, which is composed of two metal shells over the insulator at the transition from the rod to the end fitting. A cavity formed by the metal shells is then filled with a sealant.

As I said, semiconducting corona shields are known, for example from the US 6,388,197 B1 and the US 4,355,200 ,

However, such field-forming measures are relatively expensive, and are often not sufficient to actually prevent critical corona discharges. For many composite insulators, therefore, field shaping is not required. It has already been proposed for such insulators, with the help of insulating material of greater wall thickness, the insulating Enclosing the rod near the transition better to protect against erosion. Because of the greater wall thickness, it takes a correspondingly longer time until corona discharge-induced erosion penetrates the insulator wall in this particularly exposed area. The life-shortening effect of the corona discharge is thus compensated by this measure. In addition, the Koronaschirm can also serve to seal the transition between rod and end fitting, eg against rainwater. An example of a composite insulator with such a corona screen made of insulating material is from the document US 3,898,372 known.

However, that is from the US 3,898,372 known composite insulator not yet considered to be optimal in terms of life and manufacturing cost. The present invention is therefore based on the problem of providing a composite insulator with a long service life, which can still be produced with relatively little effort. This also includes the provision of a corona screen, which allows the production of such an insulator.

The invention relates to a Koronaschirm for a composite insulator, the latter comprising a rod with insulating jacket and ribs, and at least one end fitting. The Koronaschirm is one-piece and made of plastic. It is capable of being coaxially mounted on the composite insulator at the transition from the rod to the end fitting. Here, the corona screen forms an inwardly open cavity. This can be filled with sealant via at least one filling channel. He has on both sides in the axial direction on a final cuff for cavity sealing. The diameter of the rod-side end collar is adapted to that of the insulating jacket, and the diameter of the fitting-side end collar is adapted to that of the end fitting. The filling channel leads from the outside to the cavity.

Another aspect of the invention relates to a composite insulator comprising a rod with insulating jacket and ribs, at least one end fitting and at least one corona screen of the type mentioned above. Insulating jacket and ribs are made of insulating plastic. The Koronaschirm is made as a separate molding. It is arranged coaxially on the composite insulator at the transition from the rod to the end fitting. Its cavity is filled with sealant.

Other features go for the expert reader from the following detailed Description of embodiments and the attached drawings.

• Fig. 1 eine schematische Darstellung eines Längsschnitts einer Ausführungsform eines Verbundisolators mit einem Koronaschirm an jedem seiner beiden Enden zeigt;
• Fig. 2 einen entsprechenden Schnitt durch einen der Koronaschirme von Fig. 1 zeigt; und
• Fig. 3 eine Ansicht in den Koronaschirm von Fig. 2 in Richtung der Isolatorachse ist.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

• Fig. 1 a schematic representation of a longitudinal section of an embodiment of a composite insulator with a Koronaschirm at each of its two ends;
• Fig. 2 a corresponding section through one of the corona shields of Fig. 1 shows; and
• Fig. 3 a view in the corona screen from Fig. 2 in the direction of the insulator axis.

Fig. 4 shows one of the Fig. 1 corresponding schematic longitudinal sectional view of the end portion of another embodiment of a composite insulator 1, in which the cavity also has two subspaces, but not as in Fig. 1 separated by the corona screen; otherwise illustrated Fig. 4 a gluing of the corona screen with the insulating cover;

Fig. 5 shows one Fig. 4 corresponding representation of another embodiment in which the cavity of the Koronaschirms not in the manner of Fig. 1 and 4 is divided into subspaces; otherwise illustrated Fig. 5 the case of a corona screen provided with a semiconducting layer and the case of separately produced ribs connected to the insulating jacket by gluing.

Before a detailed description of the figures, first different explanations to the embodiments follow.

The embodiments relate to high voltage insulators and corona shields for such insulators. "High voltage" is understood here in a general sense that includes medium voltage, high voltage (in the narrow sense) and maximum voltage, that is from 1 kV to several 100 kV.

The composite insulators according to the embodiments (hereinafter sometimes also referred to as "insulators" for short) have a centrally extending rod (that is to say the insulator longitudinal axis) (often also called core or strunk). The rod is, for example, cylindrical with a circular or non-circular cross-section. It serves to absorb tensile, compressive, shear and / or torsion forces and thus gives the insulator the necessary mechanical stability. The rod is electrically insulating and constructed, for example, from a glass fiber reinforced hard plastic (eg hardened synthetic resin). It can be massive or, for example, have the shape of a pipe.

The rod is equipped at one or both ends with a (usually made of metal) end fitting. This serves to connect the insulator to a support structure, to a conductor of an electrical line, or to another insulator, etc. In most embodiments, the composite insulator has such an end fitting at both ends. However, there are also special designs with only one end fitting in the form of an attached metal molding, at the other end then, for example, the insulating material of the insulator is formed into a fastening device (see, eg WO 03/081610 ). The following is sometimes spoken of an end fitting (singular), sometimes, however, of two end fittings. However, this is only for the sake of simplicity of the linguistic representation, and therefore does not imply that, for example, the respective embodiments relate only to embodiments with an end fitting or two end fittings - they always relate to both types of embodiments.

The end fittings are connected in the embodiments fixed to the rod. The connection is e.g. by crimping the end fitting in the region of an axially extending hole in the end fitting into which the rod is inserted. This results in an insoluble frictional press connection between the end fitting and rod.

The rod has an insulating sheath of insulating plastic and is also provided with ribs - also made of insulating plastic - which serve the Kriechwegverlängerung (often such ribs are also referred to as "umbrellas" - to avoid confusion with the "Koronaschirm" is in present text but uses the term "ribs"). In some embodiments, the insulating jacket and ribs are made of an elastomer, but it is also possible to use a non-rubbery, harder plastic (e.g., a hard rubber-like plastic). The plastic for insulating jacket and ribs is selected, for example, from the hot or cold vulcanizable elastomers (e.g., silicone, EPDM) or the thermoplastic elastomers. Preferably, it is silicone rubber, that is a silicone rubber vulcanizate, e.g. can be vulcanized by hot crosslinking. It is advantageously a silicone rubber vulcanizate having methyl and vinyl groups on the polymer chain (for example VMQ according to ISO 1629).

1. (i) Isoliermantel und Rippen können gesondert hergestellt sein. Bei einigen Ausführungsformen wird beispielsweise zunächst der Isoliermantel als durchgehendes Rohr z.B. mit Hilfe eines Extruders auf den Stab aufgespritzt; vorgefertigte Rippen werden sodann über den (teilweise oder vollständig vulkanisierten) Isoliermantel geschoben und an ihrer jeweiligen Position mit dieser z.B. durch Klebung verbunden. Die vorgefertigten Rippen können bei dieser gesonderten Herstellung von Isoliermantel und Rippen aus einem anderen Kunststoffmaterial als das des Isoliermantels bestehen;
2. (ii) Isoliermantel und Rippen können gemeinsam hergestellt sein, z.B. durch Umgießen des Stabs mit isolierendem Kunststoff. Bei solchen Ausführungsformen sind die Rippen also nicht vorgefertigt, sondern werden z.B. zusammen mit dem Isoliermantel an den Stab gegossen. Anders als bei der Verwendung vorgefertigter Rippen entsteht bei einem solchen Gießverfahren zwischen Isoliermantel und Rippe keine Gefügegrenze, etwa nach Art eines Kleb-Interfaces.

For the production of the insulating jacket and the ribs there are different possibilities:

1. (i) Insulating jacket and ribs can be made separately. In some embodiments, for example, first of all the insulating jacket as a continuous pipe, for example with the help an extruder sprayed onto the rod; prefabricated ribs are then pushed over the (partially or fully vulcanized) insulating jacket and connected at its respective position with this example by gluing. The prefabricated ribs may consist of a different plastic material than that of the insulating jacket in this separate production of insulating jacket and ribs;
2. (ii) Insulating jacket and ribs can be made together, for example by molding the rod with insulating plastic. In such embodiments, the ribs are therefore not prefabricated, but are cast together with the insulating jacket to the rod, for example. In contrast to the use of prefabricated ribs, no structural boundary is formed in such a casting process between insulating jacket and rib, for example in the manner of an adhesive interface.

In the embodiments, the composite insulator is also equipped with at least one corona screen. By "corona screen" is meant a sleeve-like structure which is arranged at the transition from the rod to the end fitting, that is, where usually a corona discharge shows the greatest eroding effect - to distinguish from the "ribs" mentioned structures, which continue towards the center of the insulator are arranged on the rod. The corona screen in some embodiments has one or more outwardly extending ribs, and thus is similar to the "ribs". In other embodiments, the corona screen, however, has no such rib-like shape. Insulators with two end fittings have i.a. two Koronaschirme, said special design with only one end fitting has accordingly only a Koronaschirm.

The corona screen is made as a separate molded plastic part, e.g. made of a plastic of the type mentioned above in connection with the insulating jacket and the ribs (that is, for example, of silicone rubber).

Those embodiments of the composite insulator, which after the o.g. Method (ii) are produced, thus forming a hybrid type, in which on the one hand the insulating sheath and ribs are made together by casting around the rod, but on the other hand, the corona or the corona are installed as separately produced molded parts in the composite insulator.

In most embodiments, the corona screen is made entirely of electrically insulating material. In other embodiments, the corona screen is partially formed of semiconducting material, for example, by the (made of insulating plastic type mentioned above) body of the Koronaschirms on its inner surface (or part of) is provided with a semiconducting layer. This can be done for example by applying a semiconductive paint. In still other embodiments, the corona screen is made entirely of semiconductive plastic, such as that referred to above in connection with the insulating jacket and ribs (eg, silicone rubber), but provided with a conductivity-inducing additive.

In some embodiments, the corona screen forms an inwardly open cavity when not yet installed. This can be filled with sealant. The corona screen has on both sides in the axial direction on a final cuff for cavity sealing. For this purpose, the inner diameter of the fitting-side end sleeve is adapted to the outer diameter of the end fitting in the area covered by the sleeve. The rod-side sealing sleeve sits in some embodiments not directly on the rod surface, but it sits on the surface of the insulating jacket. Accordingly, the inner diameter of the rod-side end sleeve is adapted to cavity sealing the outer diameter of the insulating jacket.

An "adapted diameter" of the end collars is understood here to be one which ensures sufficient sealing of the hollow space with respect to the exit of (not yet hardened) sealing compound. In other words, there is thus a fit between the corona screen and insulating sleeve, such that in some embodiments - in the not yet installed state of the corona screen - the inner diameter of the rod-side end sleeve is slightly smaller than or equal to the outer diameter of the insulating jacket (eg 0% to 30% less than the outer diameter of the insulating jacket). During assembly, the corona screen is stretched elastically so that it can be pushed over the insulating cover. The final cuff then applied insulating elastic, whereby a particularly effective and permanent seal is achieved. Accordingly, in embodiments, the inner diameter of the fitting-side end collar is slightly less than or equal to the outer diameter of the end fitting in the overlap region of interest (e.g., again 0% to 30% smaller than the outer diameter of the end fitting).

In order to fill the cavity easily with sealant, the corona screen has at least one filling channel, which leads from the outside to the cavity. The sealant is electrically insulating in most embodiments. The sealant is, for example, a cold-curing silicone gel, which forms, for example, a two-component system. The two components are mixed just prior to introduction into the cavity, and then cure after introduction into the cavity cold. The hardened in the cavity sealant then covers the lying under the cavity part of the insulator sealing. As a result, in particular the penetration of water is prevented in this area.

In addition to the sealing effect, the corona screen - as its name implies - provides some protection against the eroding effect of corona discharges by increasing the overall thickness of the insulating material on the rod near the end fitting. To enhance this protective effect, in some embodiments, the rod-side end collar extends further toward the center of the insulator than would be required solely to achieve the seal of the cavity. The said end collar thereby forms a Überwurftülle, which engages around the insulating jacket and thus increases the total thickness of the insulating material on the rod in the vicinity of the end fitting. In some embodiments, the spout surrounds the insulating jacket suitably, so is not part of the cavity in the corona screen. In some embodiments, the length of the throw-over spout occupies more than half the total length of the corona screen, in some embodiments even more than 2/3 of the total length (said lengths are related to the longitudinal direction of the insulator). In some embodiments, the collar has a conically tapered outer cross section in its center half, corresponding to the erosion effect of the corona discharge decreasing as the distance from the end fitting increases.

In some embodiments, in the manufacture of the composite insulator, the interface between the insulating jacket and the rod-side end collar is completely or partially bonded with an adhesive. For example, after installation of the corona screen, a suitable adhesive (e.g., a silicone adhesive) is inserted between the end sleeve and insulating sleeve (e.g., injected therewith with a type of injection needle). Especially with corona screens, the end sleeve or Überwurftülle inside a smaller diameter than the insulating sleeve, whereby the insulating sleeve in the assembled state elastically presses on the insulating, thus obtaining a particularly effective and durable seal.

Usually, the outer diameter of the end fitting is greater than that of the insulating jacket (since the end fitting generally receives the rod in a hole). Accordingly, in some embodiments, the outer diameter of the rod-side end sleeve is smaller than that of the armature-side end sleeve.

In some of the embodiments, the rod is crimped in a hole of the end fitting. The transition point at which the rod enters the compression region is covered by the cavity in the corona screen and sealed by sealant located in the latter.

In principle, it is possible, in embodiments in which the insulating jacket and the ribs are produced together by casting over the rod, to enclose the rod-side end of the end fitting in this casting process. Then the insulating jacket also covers the transition between rod and end fitting, and thus already provided for a seal of this transition. The Umgießen the end fitting but manufacturing technology can lead to difficulties based on the fact that the end fitting i.a. to preheat for the casting process to ensure proper vulcanization of the casting resin. Due to the i.a. Different thermal expansion coefficients of the end fitting and rod or the glass transition temperature of the rod, this heating can affect the strength of the press connection between the end fitting and rod. For this reason, when pouring over the end fitting it may sometimes be necessary to post-press the said press connection after casting. In most embodiments, the end fitting is therefore not cast around to avoid this difficulty with the insulating (of course, a preheating of the end fittings it does not need). The resulting non-jacketed transition between rod and end fitting is covered and sealed by the corona screen.

In general, the sheathing of the rod is done before the end fittings mounted on the rod and have been pressed with this example. Thus, the rod can then be used after encapsulation in the end fittings and can be pressed with these, for example, in most embodiments, the rod ends are not sheathed. It is thus in these embodiments in the end region of the rod, where he used a hole in an end fitting and is pressed with this, no insulating jacket poured. In general, the cast insulating jacket for manufacturing reasons is not exactly right up to the end area to be kept free, but already ends a short distance (eg of the order of 1 mm) before this. In addition, maintaining a clearance of this size is also useful to ensure that the rod can indeed be fully inserted into the hole of the end fitting. As a result, there is a transition point at the transition from the rod to the end fitting, where - as seen from the center of the insulator - the area of the rod pressed into the end fitting begins, at which the rod surface (initially) without cast insulating jacket is present. At this point, in principle, there would be a risk that water could penetrate between the rod and the insulating jacket and then possibly crawl along the inside of the rod. In the embodiments mentioned, however, the corona screen cavity covers this transition point with initially free rod surface, and the sealant introduced into the cavity seals it off. The corona shield thus prevents in these embodiments that water can penetrate between the rod and insulating jacket.

As already mentioned above, the corona screens discussed here are separately produced moldings. Therefore, the present description is directed not only to composite insulators equipped with such corona screens, but also to a corona screen per se which is intended to be installed in a composite insulator.

As already mentioned, the corona screen is made in one piece and made of insulating plastic and is suitable for being arranged coaxially on a composite insulator at the transition from the rod to the end fitting. The corona screen has an inwardly open cavity. This can be filled with sealant. The Koronaschirm has at its two - viewed in the axial direction - ends to a final cuff for sealing the cavity. The diameter of the rod-side end sleeve are adapted to the diameter of the insulating jacket and the diameter of the fitting end collar the Endarmaturdurchmesser. Thus, the corona screen forms a kind of "lost formwork" for the sealant, which is first introduced into the cavity in a flowable state. The first not yet cured sealant remains trapped in this formwork. After curing of the sealant this formwork remains on the insulator and protects together with the cured sealant the transition point. In some embodiments, at least one filling channel is provided for filling the cavity with sealing compound, which leads from the outside to the cavity. Some embodiments have two such fill channels, e.g. are arranged opposite each other. For example, the sealing compound is injected through one of the two channels, and the air which is displaced thereby escapes from the cavity via the other.

The filling of the cavity with sealant is in the latter embodiments, for example, as follows: A completed to the completion of the cavity composite insulator is oriented so that the two filling channels of a considered Koronaschirms run vertically; one of the filling channels is thus below the insulator axis, the other above. Then, flowable sealant from below into the lower Injected filling channel. In this case, the cavity fills gradually, and because of the effect of gravity remain in the filling from below no voids in the cavity. The displaced air escapes through the upper filling channel from the cavity. The injection takes place until the sealant begins to emerge at the top of the upper filling channel. Subsequently, the opening of the lower filling channel (and possibly also that of the upper) is closed, for example by introducing a plug, or by a self-closing member, for example an integrated Deckelchen in the filling channel, which acts as a non-return valve. Even if the upper filling channel is closed, for example, by means of a plug, the composite insulator can be brought into another position (for example, be suspended vertically) due to the then complete sealing of the cavity, without the curing of the (initially still flowable) sealing compound would have to wait ( on the other hand, if it is not closed, the composite insulator is left in a position where the upper filling channel points upward until the sealant has hardened.

As mentioned, in some embodiments, the corona shield not only surrounds the cavity in the sense of lost formwork, but rather extends axially to the center of the insulator to enhance protection from corona discharge induced erosion. The rod end collar then forms a collar which engages around the insulating jacket and thus increases the overall thickness of the insulating material on the rod near the end fitting.

For attachment of the rod in the end fitting in some embodiments in the end fitting extending in insulator longitudinal hole is formed, in which the rod is inserted and in which it is then fixed by pressing the hole wall. In some embodiments, the compression region extends to the hole entrance. The transition point between the rod and the compression region is then located at the front end of the end fitting having the hole, and the short piece present in some embodiments, on which the surface of the pressed-in rod without cast insulating jacket is located, lies axially outside the end fitting. in front of their front side. The corona shield covered in these embodiments with its cavity, the front end of the end fitting and the piece with an exposed rod surface.

In other embodiments, the hole in the end fitting has two sections of different hole diameter, of which the hole located at the entrance has a significantly larger diameter than the rod (without insulating jacket) and thus not to the compression region whereas the diameter of the portion deeper in the hole corresponds to that of the rod (without insulating jacket) and forms the crimping area. Unlike the embodiments mentioned in the preceding paragraph, here is the transition point between the rod and the compression region not outside the front end of the end fitting, but deeper inside the hole, and - seen from the center of the insulator in the axial direction - in front of the point, where the hole narrows and the second hole section forming the crimping area begins. In some embodiments, when casting the insulating jacket, the piece of bar-open bar rod located in front of the interface is made shorter than the larger-diameter hole section. In other words, in these embodiments, the insulating sheath - seen from the center of the insulator in the axial direction - so far into the hole, and said open-ended rod piece lies completely in the hole portion with a larger hole diameter. The end fitting thus covers - as seen in the radial direction - the rod piece with an open surface. Both the region of the cavity in the interior of this hole portion - which forms an inner part of the cavity - and that outside the end fitting - which forms an outer part of the cavity - are filled in the finished insulator with sealant. The transition point between the rod and the pressing area is thus repeatedly protected in these embodiments: it is doubly covered, namely for a through the hole wall of the end fitting and further through the (the hole wall surrounding) Koronaschirm; In addition, the thus formed inner and outer cavity are filled with sealant.

At the end face of the end fitting, seen in the axial direction, the hole section with a larger diameter is not closed to the insulating jacket; Rather, here is an (initially) open annular gap between insulating jacket and hole wall.

In some embodiments, in which the cavity of the corona screen extends beyond the end fitting end face in the axial direction to the center of the insulator, this annular gap serves to enter the sealing compound (flowable during filling) into the inner cavity. This ensures that the entire cavity - and not just the outer - is filled with sealant.

In contrast, in some embodiments, the corona screen is designed to completely or largely complete the annular gap on the end face of the end fitting. For this purpose, it has in its cavity, for example, a substantially radially extending step, which is intended to bear against the end face of the end fitting.

In some of these embodiments, the cavity does not extend beyond the step toward the center of the insulator. Rather, lying beyond the stage rod-side sleeve is fitting to the insulating jacket. Thus, in these embodiments, the step forms the end of the cavity in the direction toward the center of the insulator.

If, when installed, an embodiment of the corona shield with such a step on the end face of the end fitting, so the step covers the annular gap, and the Endarmatur wall in the region of the hole portion with the larger hole diameter and the step in Koronaschirm cavity separate the inner and the outer cavity from each other. The inner cavity is bounded outwardly from said aperture wall of the end fitting and from the step, while the outer cavity is bounded outwardly from the corona shield.

Strictly speaking - if the step completely sealed the annular gap - the cavity would be split by such a division into two subspaces, which are not in fluid communication with each other. In some embodiments, therefore, at least one connecting channel is additionally provided, which bridges the end fitting fitting the stage in terms of fluid communication and thus establishes fluid communication between the outer and inner cavities. The connection channel runs, for example, in the stage. The fluid communication connection of the two compartments ensures that the entire cavity (and not just the outer cavity) is completely filled with sealant, thus ensuring that the desired sealing function is fully achieved.

For the design case that the corona screen attached to the top of the insulator forms a slight depression, a further supportive measure may be provided to prevent accumulation of dirt and water, namely a rainwater drain in the form of one or more grooves on the outside of the corona screen. These protrude, for example, on at least one of the axial ends of the corona screen in the axial direction, thus forming a low point at which raindrops collect and then drip off from there. Once drained, the water no longer reaches the closer to the axis transition between the end fitting and rod.

As mentioned above, in most embodiments, the corona screen is made entirely of electrically insulating material. In other embodiments, the corona screen is partially formed of semiconductive material, for example by the base body of the corona screen is provided with a semiconductive layer (eg a semiconductive lacquer) on its inner surface (or a part of it, such as the cavity wall). In still other embodiments, the corona screen is made entirely of semiconductive plastic.

Here are some more comments on the overall production of composite insulators.

In embodiments with separately prepared ribs, e.g. applied by means of an extruder, the insulating sleeve on the rod. After their (complete or partial) hardening pulls the prefabricated (also already fully or partially hardened) ribs on the wrapped rod and brings them to their respective mounting position along the rod (which you, for example, taking advantage of their elasticity slightly expands to the displacement on the rod sheath to facilitate).

In other embodiments, however, the insulating jacket and the ribs are cast together to the rod.

Thereafter, in both embodiments at the ends in each case a prefabricated corona screen of the type mentioned above the sheathed rod is pushed, and this possibly expanded to fit over the insulation. Then the pressing of the end fittings is done on the non-wrapped bar ends. The corona shields are then pushed back so that they sit at the transition point between the end fitting and rod and cover them. Then, a sealant (e.g., two component silicone gel) is injected via a lower fill channel. The thereby displaced from the cavity air escapes through the upper filling channel. Occurs sealant in the upper filling channel, this indicates the complete filling of the cavity, whereupon the injection is terminated. If necessary, an adhesive (eg silicone adhesive) is also injected between the rod-side end sleeve (or over-molded sleeve) and insulating sleeve. After curing of the sealant and possibly the adhesive of the composite insulator is completed.

Now returning to Fig. 1 This shows a longitudinal section of an embodiment of a high-voltage composite insulator 1 with Koronaschirmen 2. The composite insulator 1 is usually mounted in a down-hanging arrangement, but can also be used for example in a horizontal or upright arrangement use. For this purpose, it has a tensile, compression, bending and torsion-resistant insulating, extending on the insulator longitudinal axis bar 3, which is made for example of glass fiber reinforced thermosetting plastic. The rod 3 is cylindrical, ie its cross section the same over the entire rod length.

On its outer surface, the rod 3 is surrounded by a jacket 4 made of insulating elastomer material. The insulating jacket 4 forms e.g. at regular intervals ribs 5, e.g. consist of the same elastomeric material as the insulating jacket 4. The ribs 5 serve the Kriechwegverlängerung. They can have different diameters, e.g. in an alternating sequence. For further creepage extension, they may e.g. be performed grooved at the bottom.

In the in the Fig. 1 and 4 The insulating jacket 4 was produced together with the ribs 5 in a common casting produced by molding the rod 3. Accordingly, are found in the Fig. 1 and 4 no structural boundaries between insulating jacket 4 and ribs 5. In the example of Fig. 5 insulating jacket 4 and ribs 5 are made separately; Accordingly, there are structural boundaries 7 between insulating jacket 4 and ribs 5 available

In the region of its two ends of the rod 3 is not wrapped; the insulating jacket 4 thus already ends in a (explained in more detail below) distance in front of the bar end.

At the ends of the rod 3 in each case an end fitting 8 is attached. The end fittings 8 are prefabricated metal moldings. A head fitting 8a, for example, serves to fix the insulator 1 to a high voltage mast and for this purpose is e.g. provided with a hole 9 for a fastening bolt. The end fitting 8 at the other end is a foot fitting 8b, which serves, for example, to attach a conductor to the insulator 1. The foot fitting 8 has, for example, a circumferential groove 10 for this purpose.

The end fittings 8 each have a receiving hole 11 for the rod 3. In a lower-lying section 12, this receiving hole 11 in the not yet assembled state of the insulator 1 an inner diameter which is only so much larger than the outer diameter of the rod 3, that this can be used without much effort in this deeper hole section 11. After insertion of the rod 3, the end fitting 8 is externally compressed or "crimped", in an area which corresponds approximately to the deeper hole portion 12. This area forms the so-called crimp area; he is in Fig. 1 denoted by 12a. By crimping the end fitting 8 in the crimping area 12a permanently plastically deformed so that the wall of the deeper hole portion 12 presses with relatively great force on the rod 3, whereby a non-releasable frictional connection between the rod 3 and end fitting 8 is made.

In a closer lying at the hole entrance hole portion 13 of the inner diameter of the hole is larger, namely by so much larger than the outer diameter of the insulating jacket 4, that the thus formed annular space between hole wall and insulating jacket with the flowable sealant can be filled.

The length of the non-enveloped rod end is slightly larger than the length of the deeper hole portion 12. Thus, the compressed with the end fitting 8 part of the rod 3 is not wrapped (the press connection thus exists between the end fitting 8 and 3 bar, but not insulating jacket 4). The insulating jacket 4 extends - seen from the center of the insulator 1 - in the hole section 13 with a larger diameter. However, it already ends somewhat before the beginning of the lower-lying hole section 12 in order to avoid that the insulating jacket 4 rests with its end against the constriction at the transition from the hole section 13 to the hole section 14. Thus, between the end of the insulating jacket 4 and the beginning of the lower-lying hole section 12, there is a short bar section 14 with firstly open (i.e., initially uncovered) bar surface. In the hole section 13 is thus - seen from the center of the insulator 1 - first a piece of rod 3 with insulating jacket 4, whereas deeper in the hole section 13 of the rod portion 14 is initially exposed rod surface.

At the transition region 15 between the rod 3 and the end fitting 8, a corona shield 2 made of insulating elastomer is arranged in each case. The Koronaschirm 2 is a separately prefabricated molding (so he did not like the insulating jacket 4 and the ribs 5 made by casting on the rod 3). The molding of the corona screen 2 has in its interior a cavity 16 which is open towards the inside (ie rod / insulating sheath / end fitting) and which is closed to the outside by the corona screen 2. To carry out the provided with the insulating jacket 4 rod 3 and the end fitting 8, the corona screen 2 in the axial direction in each case a suitable through hole. This is adapted with its inner diameter to the outer diameter of the insulating jacket 4 and to the outer diameter of the end fitting 8 (in the interest here end portion of the end fitting 8), and thus forms a rod-side end sleeve 17 and a fitting end cap 18 for sealing the cavity 16 in axial direction. Since the end fitting 8 encloses the rod 3 together with the insulating jacket 4, the outer diameter of the end fitting 8 is greater than that of the insulating jacket 4. Thus, the inner diameter of the fitting end collar 18 is greater than that of the rod-side end collar 17th

The end fitting wall 19 above the hole section 13 thus covers the end of the Insulating jacket 4 and the rod portion 14 and there forms an annular space 16 a, which opens into an annular gap 20 at the end face of the end fitting 8. The inner wall of the cavity 16 forms a substantially extending in the radial direction step 21, the front side of the end fitting 8 and so closes the annular gap 20. Thus, the end fitting 8 with its wall 19 and the step 21 subdivide the cavity 16 into two compartments, namely an inner cavity 16a already introduced above as the "annulus 16a" and an outer cavity 16b. The inner cavity 16a extends around the end of the insulating jacket 4 and the portion 14. It is - as stated - radially outwardly from the wall 19 of the end fitting 8, seen in the axial direction, away from the insulator center, from the hole constriction to the hole portion 12 and, Seen in the axial direction to the insulator center, bounded by the stage 21. The outer cavity 16b surrounds the end fitting 8 in the region of the hole section 13. It is bounded radially inwardly by the wall 19 of the end fitting 8 and in all other directions by the inner wall of the corona screen 2. A connection channel ( Fig. 2 ) provides fluid communication between the two subspaces 16a, 16b.

The cavity 16 (both the inner and the outer cavity 16 a, 16 b) is completely filled in the finished insulator with a cured, electrically insulating sealant 22. The sealant 22 thus covers in particular the end of the insulating jacket 4 and the portion 14 with initially exposed rod surface in the inner cavity 16 a sealingly.

Externally, the corona screen 8 has a radially extending rib 26, which serves the Kriechwegverlängerung. Moreover, he has on the outside of his fitting-side end sleeve groove-like projections 23, which serve as rainwater drainage.

FIG. 2 now shows one of the in Fig. 1 only schematically illustrated corona in one of FIG. 1 corresponding sectional view. Fig. 3 is a corresponding view in the axial direction. Because of the larger magnification are in the FIGS. 2 and 3 more realistic proportions and additional details shown. Different to FIG. 1 show the FIGS. 2 and 3 the Koronaschirm in the state in which it is present as a prefabricated, not yet installed molding. In particular, in this state, the cavity 16 is not yet filled with sealant.

As already related to FIG. 1 has been explained, the Koronaschirm 2 has a rod-side end sleeve 17 smaller diameter and a amaturseitige final cuff 18 of larger diameter. The inside diameter of the end cuffs 17, 18 are smaller by a strain amount Δd than the outer diameter of the insulating jacket 4 and as the outer diameter of the end fitting 8 (FIGS. Fig. 2 ). When installed, the end cuffs 17, 18 are elastically stretched by Δd, hence the term "elongation dimension". The expansion amount Δd is between 0 and 30%, based on the outer diameter of the insulating jacket 4 and the end fitting 8.

The cavity 16 has at its widest point an inner diameter which is slightly larger than that of the larger (ie the fitting side) end collar 18. The step 21 closes off the cavity to the rod-side end collar 17; as related to FIG. 1 has been explained, this step 21 forms a contact surface for the end face of the end fitting 8 for closing the annular gap there 20. In the in Fig. 1 In the embodiment shown, the cavity 16 does not continue beyond the step 21 in the axial direction toward the insulator center. Rather, at the stage 21 already begins on the insulating jacket 4 tight-fitting end collar 17. This is formed in the axial direction to the insulator center significantly longer than would be required only to seal the cavity 16. The end sleeve 17 thus forms a throw-over sleeve for the insulating jacket 4, which increases the wall thickness of the insulating jacket 4 in the particularly erosion-prone area of the bar 3 near the end fitting 8. The outer contour of the Überwurftülle 17 narrows conically, seen in the direction of the insulator center.

In stage 19, a plurality of (here two) connection channels 24 run, which establish fluid communication between the partial spaces 16a, 16b (which are formed during installation). In order to be able to easily fill the cavity 16 with sealing compound 22 from the outside, several (in this case two) filling channels 25 are also provided. These extend in the radial direction from the outside of the corona screen 2 to the cavity 16. The two in the embodiment of FIG. 2 existing filling channels 25 are arranged opposite one another. If the corona screen 2 is thus oriented so that one of the filling channels 25 points downwards, the other points upward. The same applies to the arrangement of the two connecting channels 24th

The connecting channels 24 are in the form of elongated recesses which open in the inner wall of the cavity 16, and in particular in the step 21. They each begin at the inner mouth of the respective filling channel 25 and lead from there to the step 21 and further in the step 21 radially inward, and finally open in the inner cavity 16a at the beginning of the rod-side end sleeve 17. When installed, the step 21 at the end face of Armaturwandung 19 is applied, so the sealant 22 in the connecting channel 24 on the front side of the wall 19 flow past. Since the connecting channel 24 is open to the inner cavity 16a, the sealing compound 22 can escape immediately after passing this obstacle from the connecting channel 24 and thus reach the inner cavity 16a and fill it.

The filling of the corona screen 2 with flowable sealing compound 22 takes place, for example, as follows: The corona screen 2 is already placed in the correct position on the transition region 15 of the composite insulator 1. The corona screen 2 or the insulator 1 has also already been rotated into such a position in which the filling channels 25 extend in the vertical direction. The sealing compound 22 is then injected gradually through the filling channel 25 located below. The mirror of the sealant 22 increases continuously in the cavity 16, initially only in the outer cavity 16b, and then also in the inner cavity 16a due to the flow through the lower communication channel 24. Air displaced by the sealant 22 exits the inner cavity 16a through the uppermost communication passage 24, and the cavity 16 entirely through the uppermost fill passage 25. Existence of sealant 22 from the uppermost fill passage 25 indicates that the entire cavity 16 is filled ; the filling process can then be stopped. In order to prevent leakage of uncured sealing compound 22 after removal of the injection device, the lower and optionally also the upper filling channel 25, e.g. closed with a stopper.

Fig. 4 shows one of the Fig. 1 corresponding schematic representation of a longitudinal section of another embodiment of a composite insulator 1 ', wherein only one end of the insulator 1' is shown here. The embodiment of the Fig. 4 is different from the one of Fig. 1 in that the inner wall of the corona screen 2 'does not abut the end face of the wall 19 of the end fitting 8, but is spaced therefrom. Although one can also speak here of an inner cavity 16a and an outer cavity 16b, the Koronaschirm 2 'thus separates these two subspaces no longer from each other; Rather, they are in fluid communication with each other via the annular gap 20. The function of the connection channels 24 of Fig. 1 So here is taken over by the open annular gap 20. The (initially flowable) sealing compound 22 thus fills the inner cavity 16 a through the open annular gap 20. Apart from the differences mentioned here, all of them are related to the Fig. 1 to 3 made statements on the embodiment of Fig. 4 to.

In the example of Fig. 4 be in the production of the composite insulator 1 ', the interface between the insulating jacket 8 and the rod-side end sleeve (or Überwurftülle) 17 have been glued with adhesive. The adhesive interface thus obtained is in Fig. 4 denoted by 27. It is understood that such a bond not on embodiments according to Fig. 4 is limited, but also in embodiments according to Fig. 1 or 5 Application can find; conversely, in embodiments of the type of Fig. 4 the Koronaschirm 2 'without such bonding application find.

Fig. 5 Finally, a still further embodiment of a composite insulator 1 "in a schematic view similar to the Fig. 4 However, in contrast to the embodiments of the Fig. 1 to 4 the attachment hole 12 in the end fitting 8 does not have a hole portion 13 of larger diameter than the rod diameter. Rather, here has the mounting hole 12 in the end fitting 8 practically over its entire length a diameter corresponding to the outer diameter of the rod 3 (without insulating jacket 4). Thus, in this embodiment, practically the entire hole 12 forms the crimping area 12a. In the absence of the hole section 13 with a larger diameter, in this embodiment the section 14 with the rod surface initially exposed is not covered by a wall of the end fitting 8, but only by the corona screen 2. "The cavity 16 consequently also has no inner and outer cavity here. but forms a uniform, outside only by the corona screen 2 "surrounded cavity.

The main body of the Koronaschirms 2 "is in turn made of electrically non-conductive plastic (eg silicone rubber), but in the example of FIG. 5 on its inner surface (except in the rod-side end sleeve 17) provided with a semiconductive lacquer layer 28. This touches the armaturseitigen end collar 18, the surface of the fitting 8 and is thus electrically at the potential of the respective end fitting 8. Mantle 4 and ribs 5 are in the example of the embodiment of Fig. 5 manufactured separately, so that between these one (eg filled with adhesive) structural boundary 7 is located.

In the example of Fig. 5 insulating jacket 4 and ribs 5 are made separately; Accordingly, there are structural boundaries 7 between insulating jacket 4 and ribs 5 available

Apart from these differences, in turn, all meet in connection with the Fig. 1 to 4 made statements on the embodiment of the Fig. 5 It is understood that the equipment with a semiconductive layer 28 and / and the separate production of insulating jacket 4 and ribs 5 not the embodiments with a Koronaschirm according to Fig. 5 are limited, but also in embodiments with a Koronaschirm according to Fig. 1 or 4 Application can find; conversely, the purely insulating Formation of the corona screen and / or the joint production of insulating sheath and ribs in embodiments with a Koronaschirm in the manner of Fig. 5 Find application.

The described embodiments show composite insulators with long life, which can be produced with relatively little effort, as well as Koronaschirme for their production.

Claims (26)

Corona screen for a composite insulator (1, 1 ', 1 "), the latter comprising a rod (3) with insulating jacket (4) and ribs (5) and at least one end fitting (8),
wherein the corona screen (2, 2 ', 2 ") is made in one piece and, made of plastic and is suitable, arranged coaxially on the composite insulator (1, 1', 1") at the transition from the rod (3) to the end fitting (8) to become,
wherein the corona screen (2, 2 ', 2 ") forms an inwardly open cavity (16) which can be filled via at least one filling channel (25) with sealing compound (22) and in the axial direction on both sides a closing collar (17, 18) for cavity sealing having,
wherein the diameter of the rod-side end sleeve (17) the diameter of the insulating jacket (4) and the diameter of the fitting-side end sleeve (18) are adapted to the Endarmaturdurchmesser, and
wherein the filling channel (25) leads from the outside to the cavity (16). A corona screen according to claim 1, wherein the rod-side end collar (17) extends further towards the center of the insulator (1, 1 ', 1 ") than would be required to achieve sealing of the cavity (16), thereby providing a collar forms to encompass the insulating jacket (4) and thus increase the thickness of the insulation of the rod (4). Corona screen according to claim 1 or 2, wherein the diameter of the rod-side end sleeve (17) is smaller than that of the fitting-side end sleeve (18). Corona screen according to one of claims 1 to 3, wherein the inner diameter of the rod-side end sleeve or sleeve (17) is slightly smaller than the outer diameter of the insulating jacket (4) and / or wherein the inner diameter of the fitting-side end sleeve (18) is slightly smaller than the outer diameter the end fitting (8) insulating jacket (4) of the composite insulator (1, 1 ', 1 "), in each case of the composite insulator (1, 1', 1") for which the corona shield (2, 2 ', 2 ") is intended, Corona screen according to one of claims 1 to 4, in the cavity (16) has a step (21) which is intended to bear against the end face of the end fitting (8). A corona screen according to claim 5, wherein at least one connecting channel (24) is provided, which fluidly bridges the end fitting (8) which bears against the step (21). A corona shield according to claim 6, wherein the connecting channel (24) extends in the step (21). A corona shield according to claim 6 or 7, wherein the communication channel (24) for fluid communication between the above the end fitting (8) lying portion (16b) of the cavity (16) and over the rod (3) lying (16a) provides. A corona screen according to any one of claims 1 to 8, wherein the corona screen (2, 2 ', 2 ") has on its outside at least one of its axial ends one or more projections (23) for drainage of rainwater. Corona screen according to one of claims 1 to 9, which is electrically insulating. Corona screen according to one of claims 1 to 9, which is made wholly or partly of semiconductive material. A corona screen according to claim 11, wherein the corona screen (2, 2 ', 2 ") is formed by an insulating body having on its inside a semiconducting layer. Corona screen according to one of claims 1 to 12, wherein the corona screen (2, 2 ', 2 ") is made of silicone. Composite insulator, comprising: a rod (3) with insulating jacket (4) and ribs (5), being made of insulating plastic, at least one end fitting (8), a corona screen (2, 2 ', 2 ") manufactured as a separate molding according to one of claims 1 to 13, arranged coaxially on the composite insulator (1, 1', 1") at the transition from the rod (3) to the end fitting (8) is and whose cavity (16) is filled with sealant (22). Composite insulator according to claim 14, wherein the corona screen (2, 2 ', 2 ") is extended by a throw-over sheath (17) towards the center of the insulator (1, 1', 1") which surrounds the insulating sheath (4) and thus the thickness of the insulation of the rod (3) increases. Composite insulator according to claim 14 or 15, wherein the interface between the insulating jacket (4) and the rod-side end collar or spout (17) is fully or partially glued with an adhesive. Composite insulator according to one of claims 14 to 16, wherein the rod (3) in a hole (12) of the end fitting (8) is pressed with this, and the transition point at which the rod (3) enters the compression region (12a), is covered by the cavity (16, 16a) and sealed by sealing compound (22) located therein. Composite insulator according to one of claims 14 to 17, wherein the end fitting (8) is not encapsulated, wherein the rod (3) in a hole (12) of the end fitting (8) is pressed with this, and in the compression region (12) no insulating jacket ( 4) is poured. Composite insulator according to claim 17 or 18, wherein at the transition to the compression region (12) is a piece of rod surface without molded insulating jacket (4) is present, and
wherein the sealing compound (22) covering this piece of rod surface sealing. A composite insulator according to any one of claims 17 to 19, wherein the crimping portion (12a) is located in a lower portion (12) of the hole while the hole in front thereof has a portion (13) of larger diameter than the insulating sheath (4), and the insulating sheath (4) - viewed from the center of the insulator (1, 1 ') in the axial direction - extends into the hole, so that the end fitting (8) - seen in the radial direction - the transition point, at which the rod enters the compression region (12a) covers, whereas the end fitting (8) forms an annular gap (20) at the hole entrance between insulating jacket (4) and hole wall (19). A composite insulator according to claims 19 and 208, wherein the piece of bar surface without cast insulating jacket (14) lies inside the hole in the larger inner diameter portion (13). Composite insulator according to claim 20 or 21, wherein the cavity (16) of the corona screen (2) has a step (21) and the end face of the end fitting (8) abuts against this step (21), so that the step (21) forms the annular gap (21). 20) and the end fitting (8) and the step (21) divide the cavity (16) into an inner (16a) and an outer (16b) cavity. Composite insulator according to one of claims 14 to 22, wherein the insulating jacket (4) and ribs (5) are made together by encapsulating the rod with insulating plastic. Composite insulator according to one of claims 14 to 22, wherein the insulating jacket (4) and ribs (5) are made separately. Composite insulator according to one of claims 14 to 24, wherein the insulating jacket (4) and / or the ribs (5) are made of silicone. Composite insulator according to one of claims 14 to 27, wherein the sealing compound (22) is a silicone gel which is cured in the finished composite insulator (1, 1 ', 1 ").

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