WO2001039344A1

WO2001039344A1 - Field control body

Info

Publication number: WO2001039344A1
Application number: PCT/EP2000/011620
Authority: WO
Inventors: Karl-Heinz Osterwohldt; Stephan SCHÖNING; Mehmet Karabacak
Original assignee: Nkt Cables Gmbh
Priority date: 1999-11-25
Filing date: 2000-11-22
Publication date: 2001-05-31
Also published as: DE20022928U1

Abstract

The invention relates to a field control body consisting of an elastomer, for controlling the electrical field of a conductor at a high level voltage. Said field control body (8) is a hollow cylinder with at least one first area (12) with a first length (L1) for placing on a semi-conducting layer (21) of the conductor insulation (20) and a second area (16) with a second length (L2) for placing on a conductor connector (32), with a second wall thickness (A') in the second area (16), which is determined by the insulation thickness of the elastomer, and a conductive layer (18) on the outer surface of the field control body (8), said layer being at earth potential. The invention provides for a first wall thickness (D) in the first area (12) that is not greater than a minimum determined by the tensile strength of the elastomer, and the wall thickness increases to the second wall thickness (A') between the first (12) and second area (16) over a section (L3), the length of this section (L3) at least corresponding to the insulation wall thickness.

Description

Field control body Description

The invention relates to a field control body - preferably in cable fittings - made of a stretchable insulator material for controlling the inhomogeneous electrical field profile of a conductor surrounded by conductor insulation at the voltage level, in particular at the high voltage level.

So far, there have been different concepts for controlling the electrical field profile, with capacitive control being used frequently. Here, in the transition area at the end of the outer conductive layer of the conductor insulator material above the conductor and in contact with the said conductive layer, a separate field control element is used, which is designed according to a specific profile (for example the Borda profile) and can also be integrated with the material. The field control body according to the invention can be manufactured and used on its own, or can be integrated in a cable fitting (sleeve). The production and use of such field control bodies leads to higher manufacturing and cost expenditure.

A field control body without field control elements in the end areas is shown in DE-AS 27 50215. This is a multi-part object consisting of an inner and an outer electrode and an insulating body with relatively coarse dimensions, which can be produced in a multi-stage manufacturing process. The material required for the outer electrode is particularly high, which is disadvantageous since conductive elastomers are particularly expensive.

It is an object of the invention to propose a field control body that is inexpensive and easy to assemble.

The solution is that in a third area between the first and second area over a third length, the wall thickness increases from a relatively small wall thickness in the first area, with a finite length of the wall thickness of the first area, to the second wall thickness, and the field-controlling effect in The first area is achieved by a thin coating that is present on the outer surface of the field control body and that is indirectly, but not necessarily, contacted with the conductive layer of the cable. This is a solution - as a capacitive control measure - in which there is no field control element in the first area. The associated change in the field control body simplifies the construction with the same functionality. The field control body can be optimized according to material parameters, in particular with regard to its mechanical strength values.

Further refinements of the invention are presented in the subclaims. The field-controlling function is achieved solely by the shape of the first and third areas. The field-controlling medium preferably has no direct contact with the outside

Conductive layer of the conductor insulation.

The field control body should preferably be used for a cable in the medium voltage range (12 to 36 kV), whereby the field control body can be used both on one-piece sleeves, cable plug-in parts or cable terminations and as a separate field control body in multi-part sets. For multi-part versions, it should be noted that only the area of the field control body is provided with an outer conductive coating that is not covered by the set. Known techniques of elastomer processing, preferably hot-curing silicone (liquid silicone rubber), are used for the production of the field control body. The type of processing and the material used depend on the number of items manufactured. The injection molding process with vulcanization at elevated temperature is appropriate for the production in large series, since shorter cycle times are possible due to the applied pressure and higher temperature. For smaller quantities, a manual casting technique with thermal treatment at room temperature may be indicated. The basic body of the proposed object is formed in a tool, and the outer conductive coating is applied in a second operation. This can preferably be applied as an electrically conductive dispersion by means of a spray. In a second process step, this coating also vulcanizes at room temperature or at elevated temperature. A few micrometers are required as the layer thickness of the outer conductive coating.

Because of the relatively small wall thickness of the field control body, an improvement in handling during assembly is achieved. For example, the field control body can be stretched so far that it can be slid over the outer sheath of the medium-voltage cable in its parked position before positioning on the cable splice. Known field control bodies do not allow such widening. In this way, sets with very short overall lengths can advantageously be realized. In addition, the stripping of the cable jacket can be reduced to a necessary minimum.

Preferred configurations are as follows:

In the first area of the field control body there is a first wall thickness which is not thicker than a minimum due to the material strength of the insulation material. The wall thicknesses are in the range of a few millimeters.

The material strength - and thus the minimum wall thickness - can be determined by the tensile strength when stretched. The required expansion depends on the application, since the ratio of the diameter of the conductor insulation to the diameter of the cable jacket depends on the power (on the electrical cross-section) of the conductor. For bridging large diameters Therefore, a multi-part field control body is proposed, which is described in particular in FIG. 4.

The wall thickness in the first area should not be thicker than a minimum due to the dielectric strength of the insulation material - in relation to the maximum permissible operating voltage of the field control body. In a further embodiment, one can take into account that the field-controlling effect of the first and second areas is due to the electrical parameters of the structure of the field control body to be considered as a cylindrical capacitor are determined. The essential parameters here are the dielectric constant and the wall thickness of the insulation material, with both variables also having a certain interaction that has to be taken into account.

The dimensions, in particular the inner diameter (inner cross-section) of the essentially hollow cylindrical field control body are selected so that certain strains (1 to 5%) are still present in the installation position, so that this provides sufficient pressure for the support on the cable splice or the Conductor connector including conductor insulation is available. Preferably, the procedure is such that the largest inner diameter of the sleeve body is approximately 1.25% smaller than the outer diameter of the conductor insulation freed from the conductive layer - designed for the smallest cable cross section in a multi-area application. The contact pressure can also be increased by using an outer sleeve or a protective sheath (as a heat shrink tube), which is usually always necessary. With these measures, the field control body can not only be used for a specific cable cross-section, but there are still applications for other cross-sectional dimensions.

The inner cross section of the field control body - either circular or sector-shaped - is constant over its entire length in its simplest embodiment. To increase the contact pressure in the first area, however, the inside diameter of the field control body in the first area can also be selected to be smaller than in the second area.

The transition of the wall thickness in the third area between the wall thickness of the first area and the wall thickness of the second area can increase linearly or a preferably concave contour is selected. One of the possible contours can be designed in such a way that, starting from the first area, there is a gradual rise, which changes to a steep rise towards the second area.

To improve the ability to be pushed on, the open end of the first region can have a funnel-shaped widening. This is an outward enlargement of the inside diameter, which can be conical, oblique, with an arc or in a certain contour. As an alternative to this, the wall thickness in the first region cannot be constant over the entire length of the first region, but the wall thickness can be designed to taper down to the inside diameter of the first region.

The most important use of the field control body is that of a sliding sleeve. It is important here that in the slide-on technique no conductive particles get into the area of the smoothing sleeve or into the interior of the clothing. In order to avoid the abrasion of conductive particles during the pushing on, a preferred embodiment is proposed in which the conductive coating applied on the outside is not led down to the inside diameter or is not led around the edge. This also ensures that the outer conductive coating of the field control body does not touch the conductive layer of the conductor insulation. However, this is not important for the electrical function of the field control body.

Compared to a field control body of the simplest design, more than three areas can be formed on a field control body of a different design. Such a field control body would have a central, second area, which is adjoined on both sides by an area which is variable in the wall thickness and a first area. This configuration can also be symmetrical with respect to the central area.

As already mentioned, the conductive coating can be in the form of a conductive material layer integrated into the surface of the insulation material - preferably made of the same base material as the insulation material - or by means of an applied layer of wire mesh or comparable metallic covers (for example a metal foil or a copper mesh) Hose). The coating is contacted with earth potential. The types of coatings - i.e. conductive, material-integrated coating and metallic covering - can also occur in combination.

A smoothing sleeve made of conductive insulating material can be integrated in the second area, or such a smoothing sleeve is designed as a single element. A single element has the advantage that it can be applied to the conductor connection part in a desired position separately from the field control body before assembly.

The field control body can be constructed from partial bodies. A possible embodiment is that the field control body consists of two partial bodies that can be pushed onto one another. The sub-bodies are axially symmetrical. The region in which the partial bodies pushed onto one another are preferably cylindrical. The part bodies can be separated on a cylindrical joint. See also the description of FIGS. 3A and 3B. The object according to the invention can in particular also be used for cable plug connections, in which case the embodiments with partial bodies can preferably be used. Depending on the application, cable connectors have a more or less complicated structure. When using the field control body, for example in an angled, two-part cable connector, training with partial bodies has particular advantages. Reference is made in detail to the description of FIG. 6.

Embodiments of the invention are shown in the single figures. They show in detail

1 shows a field control body in section,

2 shows a field control body for a cable connection,

3A and 3B each have a two-part field control body,

3C a one-piece field control body, FIG. 4 a cable connection on the one hand with field control body according to the invention and on the other hand with conventional field control,

Fig. 5 shows a further formation of the contour in the third area and

Fig. 6 application of the field control body with an angled, two-part cable connector.

A first embodiment of the invention is shown in FIG. 1. It shows an axially symmetrical sleeve body for controlling the discontinuous field transition on an energy cable connection on average.

The field control body or sleeve body 8 made of an elastomer (preferably made of silicone rubber) has an inner cross section I, which can be circular or sector-shaped. For use with cables with sector conductors, the field control body for shielding the sector conductors is sector-shaped (with 90 ° or with 120 ° symmetry). The outer surface of the field control body 8 is coated with a conductive layer 18 (made of conductive varnish or similar material) for external field limitation. The conductive material layer 18 preferably consists of the same base material as the insulation material and is applied in a second operation - after the base body has been created, for example as a spray and vulcanized onto the base body at elevated temperature. The layer thickness in this process is only a few micrometers.

The field control body consists of at least three areas: the first area 12 with the length L1 (corresponding to the length of the support on the conductive layer 21) with a small wall thickness D, the second area 16 with a variable length L2 with a larger wall thickness A 'and the transition area 14 of length L3. Depending on the embodiment, the length L2 is composed at least of the length of the smoothing sleeve 22 and the length B, which corresponds to the wall thickness A. For the connection of two conductors 30 with conductor insulation 20 via a conductor connecting part 32 connecting the conductors, the field control body 8 can be formed on each end section of a conductor 30 according to one of the features of the claims. Preferably, the field control body can also be configured identically, ie symmetrically, on both sides of the end sections.

The length B is given at least by the radius with the dimension A (insulation wall thickness above the smoothing sleeve).

The conductor 30 of the cable carries high voltage and is surrounded by a conductor insulation 20 (for example made of XLPE) of thickness E. The conductor insulation ends (coming from the left) at point P3. The conductor insulation is surrounded by a thin conductive layer 21, which ends at point P1. The area of the conductor insulation between points P1 and P3 is freed from the conductive layer. A conductor connector is indicated by reference numeral 32. The conductive coating 18 of the clothing is separated in the region 12 by the wall thickness D from the outer conductive layer of the cable, which advantageously enables a simple cable jacket test, for example in the case of cable plug-in parts.

The first region 12 with wall thickness D lies on the end of the conductive layer 21 with a length L1. To facilitate assembly, the diameter at reference number 19 is flared, so that there is an improvement in the sliding movement.

The field control body 8 has an integrated smoothing sleeve 22 made of conductive elastomer (preferably silicone rubber) in the second region 16 and lies with this region partly on the end of the conductor insulation 20 and partly on the conductor connector 32. The thickness of the smoothing sleeve 22 is selected depending on the material and is relatively small compared to the wall thickness A in the second region 16. The wall thickness A corresponds to the material-dependent insulation wall thickness of the elastomer at the voltage level at which the conductor is located and at which the field control body is used. The wall thickness A '(including the thickness of the smoothing sleeve) of the second region 16 is continued over a length L2 (less distance B) in the direction of the conductive layer 21 with a constant value.

The boundary of the intermediate area 14 with the second area 16 is designated by the point P2. Between points P1 and P2, the wall thickness changes linearly along the length L3 from wall thickness D to wall thickness A '. The length L3 corresponds at least to the insulation wall thickness of the elastomer used for the field control body. The insulation wall thickness is determined by the maximum permissible nominal voltage of the arrangement.

The wall thickness D of the first region 12 can taper towards its open end down to the inside diameter I of the first region 12. With respect to Fig. 1 would this training run approximately so that from the line labeled P1 to about

Double arrow at "D" the wall thickness of the first area is constant, and then tapers to the left, in which case the funnel-shaped design 19 is not present. An area with finite wall thickness is needed in the first area in order to achieve sufficient pressure or contact forces.

After the field control body has been installed, a copper fabric tape with earth potential connection and a protective cover (for example as a heat shrink cover) are usually pulled over the field control body.

In Fig. 1, the right end of the field control body is not shown completely. A complete field control body 8.1 on a cable splice is shown in FIG. 2. It represents a field control body that is symmetrical on both sides. The reference numerals correspond to those in FIG. 1.

A two-part field control body is shown in FIGS. 3A and 3B. The field control bodies each consist of an inner part body (8.2 or 8.3) and an outer part body 8.4. The outer partial body 8.4 has a wall thickness A2 and contains an integrated smoothing sleeve 22 "and is preferably cylindrical on the inside and outside. The outer surface is covered with a conductive coating 18 '. The outer, tubular partial body 8.4 sits above the cylindrical parting line Tr on the inner one Partial body which is formed with a linearly increasing region L3 in Fig. 3A and with a short and strongly curved region L3 (concave contour) in Fig. 3B. The inner part body has a wall thickness A1 below the outer part body. The inner part is up to the parting line Tr Partial body also covered with a conductive coating 18.

FIG. 3C shows a field control body 8.5, the shape and cross section of which corresponds to the field control body from FIG. 3B, with the difference that the field control body 8.5 is formed in one piece, that is to say it has no separation between two partial bodies. Covering by a metallic fabric 18 'is drawn on the conductive coating 18. This covering also covers areas which are formed without a conductive coating, such as the end face S of the partial body 8.4.

Another exemplary embodiment is shown in FIG. 4 with a one-piece field control body 8.6. In the right part of FIG. 4, a conventional field control is shown with KS; with the following details: 21 cables; 27 cable shield wires; 20 '"conductive layer; P3'" end of the conductive layer; 40 sleeve body with integrated control body 42 with a specially designed profile; 32 "conductor connector, or a metal sleeve surrounding the conductor connector. The inside diameter of the field control body 8.4 is larger in the area of the conductor connector 32" than in the left area (L1, L3). However, the inside diameter of the field control body 8.6 can also have its entire length constant, and only by expansion in the area of the conductor connector

32 "enlarged.

The field control body according to the invention is preferably designed as a slide-on component. However, it is also possible to mount the field control body on an expansion body - also in several parts - and to position the field control body on the splice connection during assembly from this expansion body.

There are applications in which a smoothing sleeve does not have to be present. One such case is the use of the field control body on a cable connector. The field control body can be designed in such a way that the surface of the field control body is only abutted with a conductive coating 18 in the areas L1, L2 and in the area L3 up to the conductive layer of the plug, but not in the plug itself.

5 schematically shows a further embodiment 8.6 'of the field control body 8.6 with a certain contour in the third area. The radius R (see FIG. 1) is drawn in for clarification. A copper fabric tape 18 "can lie over the outer conductive coating.

As already mentioned, the object according to the invention can also be used in particular for cable plug connections. The subject of the invention is on the

In Fig. 6, a two-part angled cable connector is shown, which connects the cable to a device. The construction of such cable connectors is part of the prior art. The reference symbols in FIG. 6 correspond to the reference symbols used hitherto, or they have been expanded with an S for the special connector design. The field control body 8S is in two parts with a first partial body 8.2S and a second partial body 8.4S. constructed, and thus corresponds to the principle shown in Figures 3A or 3B.

The first partial body 8.2S encloses the stepped cable end in an area which extends from the folded back shield wires provided with earth potential connection to the end of the conductor insulation 20. Along the length of the zone in which the shield wires and the conductive layer are covered, the wall thickness of the partial body 8.2S is relatively thin, as it corresponds to the principle of the invention. The field control body covers the conductive layer over the length L1; at the cable-side end of the field control body, the field control body covers the shield wires with an equally small wall thickness. As mentioned, the design with a small wall thickness makes assembly particularly easy. On the length of the area of the partial body 8.2S that lies on the exposed conductor insulation, the partial body 8.2S is cylindrical on the outside. The second partial body 8.4S lies on this cylindrical outer surface and extends to the contact side of the cable connector. A smoothing sleeve 22S covers the end of the partial body 8.2S the conductor connector 32S to the connecting element which makes contact with the device-side connection.

The shield wires are connected to the earth potential. The surface (reference number 18S) of the field control body is contacted via a - as is also customary with such cable plugs, via a connecting wire with earth potential and also with the housing of the device.

Claims

claims

1. Field control body (8) made of an expandable insulator material (10) for controlling an inhomogeneous, electrical field profile at the end section of a conductor (30) surrounded with conductor insulation (20), with a first region (12), with a first length (L1) of the first area (12) for resting on the end section of the conductor insulation (20) which is covered with a conductive layer (21) and with a second area (16) with a second length (L2) for resting on a conductor connection part (32) is provided and contains an electrical control sleeve (22), and in the second region (16) there is a second wall thickness (A ') which is at least equal to the insulation thickness (A) at the maximum permissible nominal voltage when the insulator material (10) is used , and with a minimum length (B) of the second region (16) necessary for insulation, the wall thickness of a wall member being in a third region (14) between the first (12) and second region (16) over a third length (L3) Thickness (D) in the first area (12), which is not thicker than a minimum due to the material strength of the insulation material (10), increases to the second wall thickness (A ¹ ) with a finite length of the wall thickness (D) of the first area ( 12) and the field-controlling effect in the first area (12) is achieved solely by a conductive coating (18, 18 ") that can be contacted with earth potential on the outer surface of the field control body (8).

2. Field control body according to claim 1, characterized in that the material strength is determined by the tensile strength when stretched.

3. Field control body according to one of the preceding claims, characterized in that the wall thickness (D) in the first region (12) is not thicker than a minimum due to the dielectric strength of the insulation material (10).

4. Field control body according to one of the preceding claims, characterized in that the wall thickness in the third region (14) increases linearly.

5. Field control body according to one of claims 1 to 3, characterized in that the wall thickness in the third region (14) increases with a concave contour.

6. Field control body according to one of the preceding claims, characterized in that the inner cross section (I) of the field control body (8) is constant over its entire length.

7. Field control body according to one of claims 1 to 5, characterized in that the inner cross section (I) of the field control body (8) in the first region (12) is smaller than in the second region (16).

8. Field control body according to one of the preceding claims, characterized in that the inner cross section (I) of the field control body (8) is circular or sector-shaped.

9. Field control body according to one of the preceding claims, characterized in that the field control body (8) consists of two axially symmetrical partial bodies (8.2; 8.3; 8.4).

10. Field control body according to claim 9, characterized in that the partial body (8.2; 8.3; 8.4) have a cylindrical parting line (Tr).

11. Field control body according to one of the preceding claims, characterized in that the inner diameter of the open end (19) of the first region (12) is continuously increased.

12. Field control body according to one of claims 1 to 10, characterized in that the wall thickness (D) of the first region (12) to its open end down to the

Inner diameter (I) of the first area (12) tapers out.

13. Field control body according to one of the preceding claims, characterized in that the conductive coating (18) is a material layer integrated into the surface.

14. Field control body for a connection of two conductors (30) with conductor insulation (20) via a conductor connection part (32), characterized in that the field control body (8) is designed according to one of the preceding claims on each end section of a conductor (30).