Patent Application
20110030994
The present disclosure relates to a high-voltage insulator, a method for producing a high-voltage insulator, and a cooling element having the high-voltage insulator.
A high-voltage insulator of the aforementioned type is described in DE 694 762 C. This high-voltage insulator has a metal cap and a bar insulator joined to the metal cap. Formed in the metal cap is a groove, into which an annular clamping head of the bar insulator penetrates, thereby forming the joint. A hollow space present between the cap and the clamping head is filled with a layer of a hardening binder. To introduce the binder and to ensure uniform curing of the same, the cap is provided with channels. To prevent penetration of water, these channels are closed with an elastic compound after the binder has been introduced and cured.
The production of such a high-voltage insulator is relatively complex, since the binder has to be introduced from the outside through the metal cap into the hollow space delimited by two joining parts. Moreover, when the binder is introduced through the channels, air bubbles or water can get into the hollow space and thereby reduce the dielectric strength of the insulator.
DE 533 573 C describes a high-voltage insulator used as a support for a high-voltage line, with a hollow insulating body, which is closed at one end, is cemented into a grounded mount and carries a cap supporting the high-voltage line.
CH 89 623 A describes a high-voltage insulator in which the outer surface of an insulating body has within a hollow metal cap, a bead-like thickening, beyond which the cap protrudes. A high electric field strength, and consequently partial discharge or creepage sparking, at the triple point of the metal cap, insulating body and air are thus avoided.
A further high-voltage insulator is described in WO 2006/053452 A1. The high-voltage insulator described is part of a hollow cooling element formed as a heat pipe and serving for the removal of heat from a generator discharge line. It has in a coaxial arrangement a mechanically supporting insulating tube composed of a polymer reinforced with fibers and/or filler and of coaxially held diffusion barriers as well as two hollow metal armatures, which are adhesively bonded in a vacuum-tight manner to the two ends of the insulating tube that are respectively formed as a supporting ring. An adhesive-bonding joint is provided between an adhesive-bonding surface of each of the two supporting rings and an adhesive-bonding surface of each of the two metal armatures. The adhesive-bonding joint is made to extend from the end face of each supporting ring onto the lateral surface thereof and is filled in a vacuum-tight manner with a hardened layer of adhesive.
Fastened to one of the two metal armatures is an evaporator, which is kept at the potential of a high-voltage conductor, and fastened to the other armature is a condenser, which is kept at the potential of a grounded encapsulation. The high-voltage insulator forms an insulating clearance of a cooling element which transfers heat formed by current losses in the high-voltage conductor to the encapsulation. A working medium located inside the cooling element, such as acetone or a hydrofluoric ether, serves for the heat transfer and thereby circulates as a vapor from the evaporator through the insulating tube to the condenser, in which the vapor condenses as a liquid while giving off heat. The liquid is returned to the evaporator again through the high-voltage insulator. The high-voltage insulator therefore serves not only as an insulating clearance but also as a line for the working medium. Since this line receives a chemical medium, is exposed to a permanent temperature of 80° C., for example, and must be liquid-, gas- and vacuum-tight over many years, such as 20 years, the adhesive bonds between the two ends of the insulating tube that are respectively formed as a supporting ring and the metal armatures have to meet demanding requirements.
An exemplary embodiment provides a high-voltage insulator including a metal armature, and an insulating tube joined to the metal armature. The insulating tube is adhesively bonded to the metal armature at an end formed as a supporting ring. The exemplary insulator also includes an adhesive-bonding joint, which is disposed around an axis of the insulating tube, is delimited inwardly by a first adhesive-bonding surface arranged on the supporting ring, is delimited outwardly by a second adhesive-bonding surface arranged on the metal armature, and is filled with a hardened layer of adhesive. In addition, the exemplary insulator includes an annular groove, which is formed in the metal armature and disposed around the axis of the insulating tube, the annular groove being configured to receive an end portion of the supporting ring and, in a coaxial arrangement, having two mainly axially aligned flanks. An outer flank of the two mainly axially aligned flanks carries the second adhesive-bonding surface. An inner flank of the two mainly axially aligned flanks carries a first sealing surface centering the supporting ring. A second sealing surface is formed in the supporting ring. The first and second sealing surfaces are arranged and formed so that, when the insulating tube and the metal armature are joined, the first sealing surface and the second sealing surface slide on one another to form a seal, and the supporting ring acting as a displacement body presses adhesive that has been introduced into the groove before the joining into the adhesive-bonding joint.
An exemplary embodiment provides a method for producing a high-voltage insulator having a metal armature, an insulating tube, and an annular adhesive-bonding joint which is disposed around an axis of the insulating tube and delimited inwardly by a supporting ring of the insulating tube and outwardly by the metal armature. The exemplary method includes joining the insulating tube to the metal armature by introducing an end portion of the supporting ring into an annular groove formed in the metal armature and disposed around the axis of the insulating tube such that the joined parts are adhesively bonded to one another. Before the joining, the groove is filled at least partially with liquid adhesive distributed uniformly in the circumferential direction of the groove. During the joining, the liquid adhesive is pressed out of the groove into the adhesive-bonding joint by the supporting ring acting as a displacement body. During the pressing operation, excess adhesive and air are removed from the adhesive-bonding joint to outside the insulating tube via at least one venting opening led through the metal armature.
Additional refinements, advantages and features of the present disclosure are described in more detail below with reference to exemplary embodiments illustrated in the drawings, in which:
According to an exemplary embodiment of the present disclosure, a high-voltage insulator can include a metal armature, an insulating tube, which is adhesively bonded to the metal armature at an end formed as a supporting ring, and an axially symmetrical adhesive-bonding joint disposed around the axis of the insulating tube. The adhesive-bonding joint is delimited inwardly by an adhesive-bonding surface arranged on the supporting ring and outwardly by an adhesive-bonding surface arranged on the metal armature and is filled in a vacuum-tight manner with a hardened layer of adhesive. In the case of this high-voltage insulator, the end of the insulating tube that is remote from the supporting ring can likewise be formed as a supporting ring and be connected to a further metal armature by means of an adhesive-bonding joint.
Such an insulator may be used as an insulating clearance for passive cooling of a high-voltage device carrying high current, where high voltage should be understood as meaning in principle an operating voltage greater than 1 kV. However, the voltage range can be below 100 kV, for example, for apparatuses and installations carrying high current with nominal voltages of 10 to 50 kV, for example.
The current carrying capacity of such apparatuses and installations is thermally limited. For nominal currents in the range of 10 to 50 kA, for example, as carried for instance in high-current devices formed as generator switches, particularly active cooling elements (for example air-to-air heat exchangers with fans) or passive cooling elements with particularly good efficiency are therefore used, such as in particular heat pipes, which along with the high-voltage insulator defined at the beginning also include an evaporator and a heat exchanger as well as a working medium. Heat occurring in the high-voltage device as a result of power losses is used here for evaporating the working medium. The evaporated working medium is transported to an externally arranged heat exchanger, where it gives off the lost heat formed in the high-voltage device again by condensation.
High-voltage devices designed as generator switches are generally of a single-phase encapsulated design and have an internal conductor at high-voltage potential arranged in the encapsulation. Heat formed at the internal conductor by current losses should be dissipated to the ambient air through the encapsulation. This means that there should be an electrically insulating clearance between an evaporator at high-voltage potential and a condenser of the heat pipe kept at ground potential, a clearance which should be designed according to the required high voltage (e.g., 150 kV BIL). The evaporator and the heat exchanger (condenser) are adhesively bonded in a vacuum-tight manner to the two ends of the high-voltage insulator.
Since there is no need for moving parts, such as fans or blowers, in the case of such a high-power, passive cooling element, with this cooling element the lost heat can be removed from the encapsulation efficiently and at low cost. Furthermore, such a cooling element is maintenance-free. In addition, the high-voltage insulator performs several functions, especially that of carrying the working medium and that of separating the potentials of the evaporator and the condenser. The reliability of such a powerful passive cooling element and a high-voltage installation equipped with such a cooling element can be ensured if the insulator provides the aforementioned functions over many years. Such an insulator should therefore be maintenance-free over a long period of time, typically of 20 years. Such great long-term stability is dependent on an extremely low leakage rate. Loss of working medium and penetration of air and moisture are therefore avoided.
Exemplary embodiments of the present disclosure provide a high-voltage insulator that has a low leakage rate and has great operational reliability even after being in operation for many years under high levels of mechanical, electrical, thermal and chemical loading. In addition, exemplary embodiments of the present disclosure provide a method for producing this high-voltage insulator and a cooling element containing this insulator.
In the case of the high-voltage insulator according to exemplary embodiments of the present disclosure, an inner flank of a groove formed in a metal armature carries a first sealing surface, which centers a supporting ring of an insulating tube, and a second sealing surface is formed in the supporting ring. The two sealing surfaces are arranged and formed in such a way that, when the insulating tube and the metal armature are joined, the two sealing surfaces slide on one another, thereby forming a seal, and the supporting ring acting as a displacement body presses adhesive that has been introduced into the groove before the joining into an adhesive-bonding joint that is formed during the joining between an outer surface of the supporting ring and an outer flank of the groove.
The production of the high-voltage insulator is simplified by the suitable arrangement and formation of the metal armature and the insulating tube. The adhesive introduced into the groove before the joining is merely pressed into the adhesive-bonding joint by the force applied during the joining. Channels made to extend through the metal armature and serving for supplying adhesive and devices leading into the channels to produce compressed adhesive are therefore rendered unnecessary. Thus, a hardened layer of adhesive that is particularly homogeneous and kept free of undesired inclusions of air is achieved between the supporting ring and the metal armature by simple means and in a comparatively short time. Adhesive-bonding surfaces of the two parts which have been adhesively bonded to one another are covered 100% with hardened adhesive and the entire adhesive-bonding joint is completely filled with hardened adhesive.
Because of the sealing surfaces sliding on one another during the joining, and thereby forming a seal for the adhesive, during the joining, the adhesive is exposed to a static pressure that is adequate for completely filling with adhesive an adhesive-bonding joint made to extend far beyond the two sealing surfaces in the axial direction. Diffusion paths for air and water that are unavoidable in the hardened adhesive are thus kept long. Therefore, the high-voltage insulator according to exemplary embodiments of the present disclosure and a cooling element containing such a high-voltage insulator are distinguished by a very low leakage rate and by outstanding dielectric behavior, such as a high creepage resistance, for example. The high-voltage insulator and the cooling element according to exemplary embodiments of the present disclosure accordingly have great long-term stability. Moreover, even metal armatures which, after completion of the insulator, enclose a hollow space that is merely accessible from the interior of the insulating tube may thus be used in the production of the insulator.
If the end portion of the supporting ring is supported on the base of the groove, the good mechanical properties of the high-voltage insulator are additionally enhanced and virtually the entire adhesive is then pressed into the adhesive-bonding joint by the base of the groove during production, whereby a good adhesively bonded connection is achieved with little adhesive.
If the adhesive-bonding joint extends into the base of the groove and is connected at the end remote from the base of the groove to at least one venting opening that is led through the metal armature to the outside, excess adhesive and air can escape from the entire adhesive-bonding joint during the adhesive bonding of the insulating tube and the metal armature. This effectively prevents adhesive from getting into the dielectrically particularly critical interfacial region between the metal armature, the insulating tube and the air (triple point), whereby an adhesively bonded connection between the insulating tube and the metal armature of a particularly high quality in mechanical, vacuum-related and dielectric terms is ensured.
If the outer groove flank extends further in the axial direction than the inner groove flank and if a guiding surface centering the supporting ring is formed on the end of the outer groove flank that is remote from the base of the groove, this guiding surface and the centering sealing surface formed in the inner groove flank may have a small extent in the axial direction in a way that is advantageous in production-related terms, for example. Reliable centering of the insulating tube via two guiding surfaces kept at a relatively great distance in the axial direction in the metal armature is then indeed ensured.
Unavoidable mechanical stresses in the hardened layer of adhesive are reduced if the cross section of the adhesive-bonding joint decreases from the base of the groove to the venting opening. Such a cross section is achieved in a way that is advantageous in production-related terms by conical formation of the adhesive-bonding surface arranged on the insulating tube and cylindrical formation of the adhesive-bonding surface arranged on the metal armature.
If at least one rib that is made to extend mainly in the circumferential direction is formed in at least one of the aforementioned two adhesive-bonding surfaces, the diffusion path for moisture and air penetrating into the adhesive-bonding joint from the outside is then extended, and so the undesired penetration of moisture and air into the interior of the high-voltage insulator is largely avoided. At the same time, the creation of a series of small air bubbles in the axial direction at the adhesively bonded location is thus also counteracted, and so a vacuum-tight adhesively bonded location is achieved.
In the case of a method suitable for producing this or another high-voltage insulator with a metal armature, an insulating tube and an annular adhesive-bonding joint, which is disposed around the axis of the insulating tube and delimited inwardly by a supporting ring of the insulating tube and outwardly by the metal armature, before the joining, the groove is filled at least partially with liquid adhesive distributed uniformly in the circumferential direction in the groove. During the joining, the liquid adhesive is pressed out of the groove into the adhesive-bonding joint by the supporting ring acting as a displacement body. During the pressing operation, excess adhesive and air are removed from the adhesive-bonding joint to the outside by way of at least one venting opening led through the metal armature.
The liquid adhesive is therefore introduced into the adhesive-bonding joint without any air bubbles and in a well-distributed manner, whereby a vacuum-tight adhesively bonded connection is achieved in a way that is reliable and can be reproduced well. Therefore, vacuum-tight high-voltage insulators of a low leakage rate and a long service life can be produced by the method, with scarcely any rejects.
Further features and further advantageous effects of the present disclosure are evident from the following description of exemplary embodiments of the present disclosure.
In the drawings, the same reference numerals indicate identical parts or identically functioning parts. A tubular high-voltage insulator represented in
An insulator closed in this way can be filled with a working medium, such as acetone or hydrofluoric ether, for example. During fitting into a high-voltage installation, the armature 2′ can then be fastened in a thermally conducting manner to a current conductor that is loaded with nominal currents, while the metal vessel held on the armature 2 may be connected to a metal encapsulation serving for the removal of heat and at ground potential. The high-voltage insulator can then constitute a cooling element which extracts heat from the current conductor by an evaporating liquid working medium in the metal armature 2′ serving as an evaporator, and heat is thereby dissipated to the outside (e.g., outside the insulator) by condensation of the evaporated working medium on the cooled metal vessel serving as a condenser.
According to an exemplary embodiment, the two supporting rings 10, 10′ can be identically formed. As is shown in
The parts of the metal armatures 2, 2′ that are adhesively bonded to the supporting rings 10, 10′ can also be identically formed. As is shown in
To produce the high-voltage insulator, the metal armature 2 is clamped in such a way that the annular groove 23 is horizontally aligned and accessible from above (in the direction as represented in
As can be seen from
As soon as the supporting ring hits the metal armature 2, for example with its free end, the joining and displacing process is ended and the adhesive-bonding joint 30 is then completely filled with adhesive, as illustrated in
A good distribution of the adhesive 32 in the adhesive-bonding joint 30, and consequently a void-free, hardened layer of adhesive 32, is achieved by the adhesive 32 being introduced particularly uniformly in the groove 23 before the joining, for instance by turning the armature 2 and the mixer 30 with respect to one another. According to an exemplary embodiment, the cross section of the adhesive-bonding joint decreases in the direction of flow of the liquid adhesive 32, which enables the liquid adhesive to pass from the base of the groove into the adhesive-bonding joint 30 very uniformly and without any air bubbles. Therefore, a void-free hardened layer of adhesive 32 is achieved at the adhesively bonded location. In addition, the thickness of this layer of adhesive 32 increases toward the end face of the supporting ring 10. Undesired voltage increases at the end of the insulating tube 1 are thus greatly reduced.
The at least one rib 28 has the effect of extending the diffusion path for moisture and air penetrating into the adhesive-bonding joint 30 from the outside and significantly reducing the undesired penetration of moisture and air into the interior of the high-voltage insulator. At the same time, this arrangement avoids the creation of a series of small air bubbles in the axial direction at the adhesively bonded location, whereby the quality and impermeability of the adhesively bonded location are additionally improved.
In a corresponding way, the insulating tube 1 may also be adhesively bonded to the metal armature 2′. This adhesive bond achieves a vacuum-tight hollow space that is merely accessible from the outside by way of the supporting ring 10 or the metal armature 2.
It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08151725.2 | Feb 2008 | EP | regional |
This application claims priority as a continuation application under 35 U.S.C. §120 to PCT/EP2009/051840, which was filed as an International Application on Feb. 17, 2009 designating the U.S., and which claims priority to European Application 08151725.2 filed in Europe on Feb. 21, 2008. The entire contents of these applications are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2009/051840 | Feb 2009 | US |
| Child | 12860550 | US |
