Plug-in device and plug-in connection apparatus having such a plug-in device
Patent Information
- Application Number
- AE202602252
- Authority / Receiving Office
- AE · AE
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-09-06
- Filing Date
- 2025-08-01
Smart Images
Figure ABST_ABST
Abstract
Description
Plug-in device and plug-in connection apparatushaving such a plug-in deviceThe invention relates to a plug-in device for detachable insertion into a receiving device for establishing an electrical connection between a high-voltage direct-current cable and a high-voltage equipment, wherein the high-voltage direct-current cable is at least partially surrounded by an insulating body, and to a plug-in connection assembly with such a plug-in device.DE 10 2004 054 639 A1 discloses a cable plug connector of a plug-in connection assembly for medium and high voltage technology, wherein the cable plug connector has a connection means which can be electrically connected to a conductor of a cable and via which an electrical connection is established between the conductor and a contact element of the mating part of the plug-in connection assembly when the cable plug connector is plugged together with a mating part of the plug-in connection assembly, and wherein the cable connector has an insulating element which has a conical surface at least in sections for electrically tight contact with an associated surface of the mating part in the mated state and which has a first section in which the insulating element accommodates the cable to be connected, wherein in the further course of a longitudinal direction the insulating element has a second section which forms the conical surface. In this way, a cable connector is created that can be used for a wide range of different cross-sections and diameters of conductors, whereby simple assembly with permanently reliable contact is guaranteed.EP 3 108 551 B1 describes a cable termination device for HVDC GIS systems with various designs. A partition made of electrically insulating material is positioned around the power cable. This divides the cable termination device into two chambers, which can be filled with different insulating media. To terminate the power cable, a control element is positioned at the level of the outer conductive layer end, whereby a peripheral material layer for non-linear resistive field control is created along the boundary surface between the control element and the cable.Furthermore, it is known from EP 3 095 161 B1 that a high-voltage cable plug prevents damage to the high-voltage cable plug or the socket element by means of a protective element applied to the end of its contact system when the plug-in connection is made in an electrically tight system.DE 10 2018 218 879 A1 further states that, in general, a high-voltage bushing has the task of insulating a high-voltage transmission line with a current-carrying conductor that is at high-voltage potential from an environment that is essentially at earth potential, for example an equipment wall of the high-voltage system. For example, the housing of a transformer can have a device connection part into which a high-voltage connector for connecting the transformer to a high-voltage network can be plugged.DE 101 39 251 C1 discloses a plug-in connection for a switchgear operated with medium voltage. A plug-in device with a metallic connection and a cable attached to it can be connected to a contact piece on a switch panel wall. This plug-in device comprises a sealing body which surrounds an end area of the cable and the metallic connection. The sealing body has an annular collar that can be positioned in the contact piece and a conductive coating that is present on the inside and outside of the sealing body.A contact plug part is known from EP 0 825 682 A2, which is suitable for a plug-in connection of high-voltage cables. This contact plug part comprises a contact pin with a contact surface that has a silver-graphite composite coating. Furthermore, the contact pin comprises a field-grading element which is provided in a silicone body which at least partially surrounds the contact pin.Based on this state of the art, the invention is based on the task of creating an improved solution compared to the state of the art, which can be used in particular for direct current in the high voltage range.A plug-in device with the features of patent claim 1 solves this problem.Since the insulating body has a boundary surface along its outer side and a field-grading element made of conductive material is arranged at a respective end area of the boundary surface, the local electric field stresses in neighboring further boundary areas of the plug-in device and the receiving device, in particular air gaps, can be controlled, as well as charge activities at the boundary surfaces between the air and the insulating material of at least one insulating body and a receiving device can be reduced to a level in order to create a safe and reliable electrical connection of a high-voltage direct current cable to other high-voltage equipment, for example in the form of gas-insulated switchgear (GIS) or transformers.The plug-in device according to the invention relates in particular to an electrical connector element for cables in the high-voltage direct current transmission range, which is also technically abbreviated to HVDC (High-Voltage Direct Current), whereby the HVDC cables (high-voltage direct current cables) in question are intended to be primarily polymer-insulated. The electrical field distribution under a direct current (DC) stress is largely determined by the temperature and field strength-dependent volume resistance of the insulating materials. In the case of unfavorable design and / or material pairing, field enhancements can occur in insulating materials with high volume resistance in the sense of field displacement, whereby further field enhancements in insulating materials and in their boundary surfaces are caused by existing space charge accumulations under direct current (DC) stress. In this plug-in device, it is provided that one insert or attachment part, in particular flat, rests against or on one end face of the insulating body, which faces the receiving device, and that the second insert or attachment part rests against or on the other end face of the insulating body, or is at least partially inserted.The plug-in device according to the invention makes it possible to homogenize the field distributions in the adjacent or neighboring boundary surfaces, in particular existing air gaps, by means of the additional field-grading element and at the same time to attenuate the charge activities, in particular at existing boundary surfaces of air / insulating material, in order to avoid unwanted flashovers or breakdowns under direct current (DC) stress.It is preferred that the field-grading elements each have an outer circumferential surface that merges flush into the boundary surface of the insulating body and each have a contact surface outside the boundary surface that merges into or adjoins the outer circumferential surface.In a preferred embodiment of the plug-in device, it is provided that the respective field-grading element is mounted and / or inserted on the insulating body, preferably in the form of a coating or in the form of an insert or attachment part, which is preferably prefabricated. It is also preferable that the respective insert or attachment part is made of elastically flexible, conductive elastomer, such as silicone rubber or ethylene propylene diene rubber (EPDM), which is preferably made of the same base material as the insulating body. In this way, the respective field-grading elements can be connected to the insulating body in a particularly easy-to-install manner, forming an entity. In particular, the respective insert or attachment part can be placed flat on the insulating body, for example as part of a vulcanization process, and connected to it, or at least one external recess is created in the insulating body, into which the insert or attachment part is preferably inserted or fitted in such a way that the outer contour of the insulating body remains essentially undisturbed.It is also preferable that conductive dispersions or conductive paint is used for the coating, which is applied as a spray application or by hand with a brush to the insulating body, preferably in a peripheral recess of the same. The coating can be applied partially to the outside of the insulating body, but largely over the entire surface; however, it is preferable that an associated recess or cut-out is also created in the insulating body for the coating, into which the respective coating is applied in such a way that the closed contour of the outside of the insulating body remains undisturbed. In addition to conductive dispersions or conductive paint, other suitable coating materials can also be used if necessary.It is also preferable that different types of field-grading elements, in the form of a coating or in the form of an insert or attachment part, are used simultaneously on an insulating body. It can also be provided that the field-grading elements provided in the area of the boundary surface on the outside are of a uniform design, so that, for example, the two field-grading elements are made of a coating or in the form of an insert part or in the form of an attachment part. Any combination of two field-grading elements can also be provided. The respective field-grading element is preferably connected to the insulator without an air gap in order to lower the local electric field stresses in adjacent air gaps and reduce the direct current (DC) stress.It is preferable for the respective insert or attachment part to be designed as a closed ring body that comprises the high-voltage direct current cable. If necessary, the respective annular body can also form a torus. Seen in a radial direction, the respective insertion or attachment part thus comprises the high-voltage direct current cable, which protrudes axially from both sides of the insert or attachment part. Furthermore, it may be provided that the respective insert or attachment part is designed as a closed ring body in which an ground deflector is integrated. This enables simple manufacture and installation.The insulating body can have the shape of a truncated cone, which comprises at least one bending line on the circumference, whereby the bending line arranged at a distance from the end face of the insulating body separates the boundary surface on the outside of the insulating body from other sections, such as a bending surface, of the truncated cone.Furthermore, it may be provided that the respective field-grading element has an outer circumferential surface and a contact surface which are angled towards each other, which merge into each other in an arc or which have a polygonal shape when viewed in cross-section to the longitudinal axis of the insulating body. The respective cross-sectional design of the field-grading element can be adapted depending on the application and design of the plug-in device.According to a preferred embodiment, it is provided that a contact system is arranged adjacent to the insulating body and pointing in the insertion direction towards the receiving device, which consists at least of a contact ring and a tension cone, whereby a thrust piece is arranged between the tension cone and an end face of the insulating body. In particular, it is provided that the thrust piece has a metallic energy storage element by means of which the thrust piece is held in contact with the field-grading element to maintain an electrical connection. This allows the electrical connection to be maintained, particularly in the event of changing temperatures. A mechanical element, such as a spring or the like, can be provided as a force storage element. The thrust piece can be a metallic or an insulating part.Advantageously, a pressure sleeve is provided which abuts against the insulating body in the opposite direction to the direction of insertion into the receiving device and which has a pressing surface which abuts against the contact surface of the additional field-grading element. Furthermore, the pressure sleeve with an energy storage element can press the insulating body into the receiving device via the contact surface of the additional field-grading element. This enables the necessary contact pressure between the boundary surface of the insulating body and a contact surface of the socket of the receiving device, which increases the electrical strength of the so-called void-free interface (Edelfuge).The plug-in device advantageously has an insulating sleeve, which extends from a bell flange surrounding the high-voltage direct current cable in the direction of the insulating body, whereby one end section of the insulating sleeve overlaps the contact surface of the additional field-grading element and only partially covers this contact surface. The metallic pressure sleeve, which at least partially surrounds the insulating sleeve, lies on the uncovered area of the contact surface of the field-grading element. This allows the contact surface of the field-grading element to be in electrically conductive contact with the pressure sleeve, which is earthed. Alternatively, it can be provided that the end section of the insulating sleeve lies against a bending surface of the insulating body at a distance from the contact surface of the additional field-grading element. As a further alternative, it may be provided that the end section of the insulating sleeve, starting from the bell flange, extends at least between the pressing surface of the pressure sleeve and the contact surface of the further field-grading element in the form of the insert or attachment part, which comprises the outer circumferential surface, the contact surface and the ground deflector as a one-piece component. The contact surface of the field-grading element is not completely overlapped by the end section of the insulating sleeve.The invention also relates to a plug-in connection assembly with a plug-in device as described above, whereby known applications for such devices are, for example, dry, plug-in cable terminations for transformers and GIS switchgear, outdoor terminations and plug-in cable joints.This plug-in connection assembly has the advantage that the field-grading elements arranged in the end area of the boundary surface of the insulating body minimize charge accumulation in the adjacent and adjoining boundary surfaces and the associated field elevation, as these are dissipated via the field-grading elements and the adjacent pressure sleeve or thrust piece. At the same time, the field strength in the air gaps can be reduced.Furthermore, it is preferable that a pressure sleeve on the plug-in device presses the boundary surface of the insulating body flat against the conical contact surface of a socket of the receiving device by means of a force storage element, such as a spring assembly. This allows the necessary contact pressure to be applied so that there is virtually no air in between or an air gap is no longer formed. This prevents partial discharge or flashover in this area.At least one electrode is preferably provided in the socket, whereby the one electrode is assigned to a contact socket of the receiving device and is electrically connected to it. The outer circumferential surface of the field-grading element is positioned on the insulating body in such a way that the outer circumferential surface of the field-grading element does not exceed the height of the metallic electrode in the plugged-in state. The first electrode thus covers the outer circumferential surface of the field-grading element facing the contact socket. In addition, a further electrode can be provided in the socket, which is positioned at a distance from the first electrode and is at earth potential. It is again provided that the outer circumferential surface of the additional field-grading element does not exceed the height of the additional electrode.In the plug-in connection assembly, it is also preferably provided that a bell flange is arranged on the end face facing away from the insulating body, which comprises a flange part for establishing the flange connection with a further flange part of the socket. This allows the plug-in device to be coupled and securely connected to the receiving device in a simple manner.In the following, the plug-in device and the plug-in connection assembly formed thereby are explained in more detail with reference to embodiment examples according to the drawing. In principle and not to scale, the drawings show inFigure 1 a principle longitudinal sectional view, a plug-like plug-in device together with a socket-like receiving device, which are shown separately from each other in a connected state to form a plug-in connection assembly as a whole,Figure 2 a principle longitudinal sectional view of the plug-in device and the receiving device in a connected state to form a plug-in connection assembly according to Figure 1,Figure 3 a principle longitudinal sectional view of an alternative embodiment of the plug-in connection assembly to Figure 2,Figures 4 to 6 a sectional view of the upper half of an insulating body for the plug-in device according to Figure 1, with various types of field-grading elements both as an insert or attachment part in the insulating body and as a coating, andFigure 7 a principle longitudinal sectional view of a further alternative embodiment of the plug-in connection assembly to Figure 2 with an insulating body of a plug-in device according to Figure 6.Figure 1 shows a plug-in device 10 viewed in the direction on the left-hand side, which is provided for releasable insertion into a receiving device 12, as shown on the right-hand side viewed in the direction of view of Figure 1. Together with the receiving device 12, the plug-in device 10 forms a plug-in connection assembly 14 as a whole, which is shown in the plugged-together state in Figure 2. This plug-in connection assembly 14 is used to establish an electrical connection between a high-voltage direct current cable 16 and parts of high-voltage equipment (not shown), such as a GIS switchgear or a transformer.The high-voltage direct current cable 16 shown in detail in Figure 1 comprises a cable conductor 102 as the core, which is surrounded by an insulation 46. This insulation 46 comprises an outer conductive layer 103, which in turn is surrounded by an outer sheath not shown in detail. This high-voltage direct current cable 16 can comprise further layers or sheaths, for example to prevent water from spreading along the cable or water from penetrating into the cable and / or a discharge of fault currents. For example, the cable conductor 102 may comprise a cross-section of 1400 to 4000 mm2. The insulation 46 may have a wall thickness of at least 10 mm, preferably at least 18 mm.The high-voltage direct current cable 16 is surrounded by an insulating body 18 in the radial direction at an end region on the end face in such a way that parts of the high-voltage direct current cable 16 protrude beyond the insulating body 18 at the edges on both sides when viewed in the axial direction. If the plug-in device 10 is inserted into the receiving device 12 in a contacting manner, forming the plug-in connection assembly 14, individual air gaps 100, 101 are created between the outside of the plug-in device 10 and the inside of the receiving device 12, so that the insulating body 18 insofar at least partially delimits these air gaps towards the outside and separates them from one another.As Figures 1 and 2 further show, the insulating body 18 has at least two field-grading elements 20, 22 made of conductive material in such a way that the local electric field stresses in adjacent air gaps 100, 101 and charge activities at the boundary surfaces between the air and the insulating material of the insulating body 18 and the receiving device 12 are reduced to a level that prevents the electrical strength of the air gaps, the insulating materials and the boundary surfaces from being exceeded. The relevant field-grading elements 20, 22 are explained in more detail below.The plug-in device 10 according to Figure 1 has the spindle-shaped insulating body 18, which is designed in the form of at least one truncated cone. Accordingly, the insulating body 18 has a front free end face 28 and an opposite free end face 30. The front end face 28 points in the direction of the receiving device 12 or the end face of the high-voltage direct current cable 16. The opposite end face 30 points in the direction of a bell flange 72 of the plug-in device 10. Furthermore, the insulating body 18 has individual bending lines 32, 34, which are partially shown in broken lines in Figure 1. Between the one free end face 28 and the adjoining first bending line 32, the insulating body 18 is designed in the form of a truncated cone 36. Furthermore, between the first bending line 32 and the adjacently following second bending line 34, the insulating body 18 can be provided with a second truncated cone 38. Furthermore, a further truncated cone 40 can be connected between the second bending line 34 and the other free end face 30. Furthermore, the cone directions of truncated cone 36 and of the at least one further truncated cone 38, 40 are directed in opposite directions to one another. In continuation of the terminology, a circumferential boundary surface 42 is to be formed between the one free end face 28 and the first bending line 32 of the insulating body 18 on the outer circumference.A field-grading element 20, 22 is provided in the respective outer end region of the boundary surface 42. These field-grading elements 20, 22 are used for geometric and / or resistive field grading. These field-grading elements 20, 22 limit the boundary surface 42 in the axial direction. The field-grading elements 20, 22 comprise an outer circumferential surface 43, which preferably merges flush into the boundary surface 42. Furthermore, the field-grading elements 20, 22 comprise a contact surface 44, which is aligned outside the outer circumferential surface 43 in relation to the boundary surface 42. This contact surface 44 is preferably angled with respect to the outer circumferential surface 43. For example, the contact surface 44 of the field-grading element 20, which is assigned to the end face 28 of the insulating body 18, can run parallel to this end face 28. In the case of the opposite field-grading element 22, the contact surface 44 can extend along an outer circumference or a bending surface 33 of the insulating body 18, which is formed, for example, between the bending line 32 and an adjacent bending line 34.The insulating body 18 preferably consists of ethylene-propylene-diene rubber material (EPDM), which is available in a wide variety of compositions in the art. Instead of EPDM material, silicone rubber can also be used in a wide variety of forms. A funnel-shaped field-grading body 48, which is also referred to as a ground deflector in technical terms and which is embedded in the insulating body 18 with an outwardly widening funnel, sits on the high-voltage direct current cable 16 in a conventional design. The field-grading body 48 advantageously sits on a reworked conductive layer end 104 of the outer conductive layer 103 of the high-voltage direct current cable 16.Furthermore, the plug-in device 10 has a contact system 50 on its front side with a contact ring 52, a tension cone 54 and a thrust piece 56. The structure in this respect is also common for such plug-in devices 10, so that this will not be discussed in more detail at this point. In any case, however, it is ensured that a secure end termination is created for the high-voltage cable 16 and that the contact system 50 as a whole ensures the electrical connection to a contact socket 60 of the receiving device 12 during operation or when plugged in. The contact system 50 of the plug-in device 10 is then followed on the other side by the previously described structure with the insulating body 18.In the contact system 50 shown in Figures 1 and 2, a metallic energy storage element 59, in particular a spring device, is provided in the thrust piece 56, in contrast to the usual structure of such plug-in devices. This makes it possible to maintain permanent electrical contacting between the field-grading element 20 and the thrust piece 56 regardless of temperature fluctuations.Furthermore, the plug-in device 10 has a pressure sleeve 62 opposite the contact system 50, which presses the insulating body 18 firmly against the inner wall or contact surface 26 of the receiving device 12 by means of a spring assembly 64, as a component of a spring device 66, when the plug-in device 10 is plugged together with the receiving device 12, so that any air gap 105 is avoided or reduced in volume if possible. In addition, a lubricant or a fluid is introduced to fill the air gap. The spring device 66 always provides the required pressure or contact pressure, even in the event of thermal expansion of the insulating body, which must be compensated for. In any case, this increases the electrical strength of the boundary surface 42 between the insulating body 18 and the inner wall or the contact surface 26 of the bushing-shaped receiving device 12.Furthermore, a funnel-shaped insulating sleeve 70 is fitted between the spring device 66 and the insulating body 18. The insulating sleeve 70 acts as a barrier to prevent possible discharges along the metal / air boundary surface when a possible sheath fault occurs, for example in event of the damage to the cable sheath (not shown). The insulating sleeve 70 is used in particular to prevent breakdowns or flashovers between metallic parts, in particular the bell flange 72 and the spring device 66, and the outer conductive layer 103 of the cable 16 with the field reflector 48 contacted around it. The outer circumference of the insulating sleeve 70 is supported on the inner wall of the spring device 66 and extends to a so-called bell flange 72. The bell flange 72 widens in diameter and at least partially surrounds the pressure sleeve 62 and merges into a plate-shaped flange part 74 for establishing the flange connection with a further corresponding flange part 76 of the receiving device 12. The receiving device 12 is designed in the form of a socket 78. Furthermore, the spring device 66 is supported via the pressure sleeve 62 on the outer contour or the contact surface 44 of the field-grading element 22, so that an electrical connection is always ensured.The insulating sleeve 70 has an end section 71 that rests against a bending surface 33. The contact surface 44 of the additional field-grading element 22 is provided flush with this bending surface 33. Preferably, a distance is formed between one end face end of the end section 71 of the insulating sleeve 70 and the end of the contact surface 44 aligned with it. The pressure sleeve 62 can bear against the contact surface 44 with a pressing surface 63, which is aligned with the contact surface 44, and exert a pressing force on the contact surface 44.To complete the description of the plug-in connection assembly 14 as a whole, it should also be mentioned that the receiving device 12 comprises a socket 78, which is installed on high-voltage systems via a suitable pressure flange, which can be formed by the further flange part 76. In this respect, the receiving device 12 then forms a closed, in particular gas-tight unit with the systems already mentioned. For optimum electrical field grading, metallic electrodes 82, 84 are incorporated into the socket-shaped receiving device 12 in the socket material during its manufacture in an integrated design. The already mentioned contact socket 60 at the tapered end of the socket 78 serves to ensure the electrical connection with the high-voltage transmission line in the form of the cable 16 and the further electrode 84. Alternatively, it may also be provided that the socket 78 has only one electrode 84, which is electrically conductively connected to the contact socket 60.Figure 3 shows a schematic longitudinal sectional view of an alternative embodiment of the plug-in connection assembly to the embodiment in Figures 1 and 2. This embodiment differs in the design of the insulating sleeve 70. In this embodiment according to Figure 3, it is provided that the end section 71 of the insulating sleeve 70 extends at least as far as the contact surface 44 of the further field-grading element 22 and partially covers it. As a result, the end section 71 of the insulating sleeve 70 is arranged overlapping the contact surface 44. Preferably, it is provided that only a narrow circumferential end section of the contact surface 44 is covered by the insulating sleeve 70.In Figure 4, the insulating body 18 according to the plug-in device 10 described above in Figures 1 to 3 is shown in a schematic sectional view only with respect to an upper half. The two field-grading elements 20, 22 are preferably of the same design. Each of the field-grading elements 20, 22 has an angular shape when viewed in cross-section. For this purpose, the insulating body 18 has a recess or cutout 86 on the outer circumference following the desired angular shape, into which a coating 88, for example in the form of conductive dispersions or conductive paint, is introduced, whereby the described closed outer contour of the spindle-shaped insulating body 18 is not violated. The coating 88 can be sprayed on or applied by hand with a brush. The thickness of the coating 88 can be thin, for example between 0.03 mm and 2 mm. The application of the coating 88 should in any case avoid the formation of peaks or sharp-edged transitions at the boundary surface 42 and the bending surface 33.The course of the coating 88 for forming the field-grading element 22 is selected according to the representation according to Figures 1 to 3 in such a way that, starting from the first bending line 32, the coating 88 extends the outer circumferential surface 43 in the direction of the boundary surface 42 and the contact surface 44 of the field-grading element 22 extends in the opposite direction in the direction of a bending surface 33 of the insulating body 18. The ideal length of the coating 88 for forming the outer peripheral surface 43 is about 10 mm to 40 mm, while a length of the coating 88 along the bending surface 33 of at most one half of the entire length of the bending surface 33 should be selected.According to Figures 1 to 3, the course of the coating 88 for the field-grading element 20 is selected such that the coating 88 forms an outer circumferential surface 43 which merges flush with the boundary surface 42. Furthermore, it is provided that the coating 88 extends along the end face 28 of the insulating body 18 in order to form the contact surface 44. As an example, it is provided that the outer circumferential surface has a length of 10 mm to 50 mm and completely covers or covers the end face 28 of the insulating body 18.Figure 5 shows an alternative embodiment of the field-grading elements 20, 22. On the free end face 28 of the insulating body 18, a field-grading element 20 is attached or integrated as an insert 91, which is preferably designed as a circular sector and continues the taper of the insulating body 18 along its outer circumference. In particular, this first field-grading element 20 is flush with the free end face 28 of the insulating body 18 and is connected to it without an air gap, for example by vulcanizing its elastomeric material to the comparable elastomer of the insulating body 18. The preferred radius of the circular sector of the first field-grading element 20 is between 30 mm and 50 mm. In addition to the shape of a circular sector, the field-grading element 20 must be designed in such a way that the entire end face of the insulating body 18 remains conductive. In this respect, a field-grading element 20 made of conductive material can therefore be integrated into the conical end 28 of the insulating body 18 as an extension and, in particular, the first field-grading element 20 referred to can also be connected to the insulating body 18 as a prefabricated component in a larger number of pieces. In this embodiment according to Figure 5, an arcuate insert port 90 is inserted into a corresponding recess 86 in the insulating body 18 for the second field-grading element 22, which forms a kind of circular sector when viewed in cross-section. The preferred radius of the circular sector of the field-grading element 22 is between 10 mm and 40 mm and should not be more than one half of the entire length of the bending surface 33.A further embodiment example of the insulating body 18 is shown in Figure 6. The first field-grading element 20 corresponds, for example, to the embodiment in Figure 5. The further field-grading element 22 can again be a prefabricated insert 92 which, starting from the outer circumferential surface 43 as viewed in the direction of the end face 30 of the insulating body 18, is of polygonal cross-sectional design and is formed in one piece with the ground deflector 48, the modified insert port 92 in this respect extending as far as the boundary surface 42 as viewed in the radial direction and can thus comprise the outer circumferential surface 43, the contact surface 44, the bending surface 33 and further surface sections as far as the free end face 30. The length of the second field-grading element 22 modified in this way along the boundary surface 42 can ideally again be 10 mm to 40 mm.It should also be mentioned at this point that all components of the plug-in connection assembly 14 used are rotationally symmetrical to the longitudinal axis of the device and in particular form hollow cylindrical structures for the purpose of enabling the high-voltage direct current cable 16 to pass through.Figure 7 shows a longitudinal sectional view of a further alternative embodiment of the plug-in connection assembly 14. Here it is provided that the plug-in device 10 comprises an insulating body 18 with field-grading elements 20, 22 arranged thereon as shown in Figure 6. Due to the embodiment of the field-grading element 22 in the form of the insert port 92 according to Figure 6, it is necessary that the end section 71 of the insulating sleeve 70 extends completely along the pressure sleeve 62 or along the pressing surface 63 of the pressure sleeve 62 or at least slightly beyond it. The end section 71 of the insulating sleeve 70 extends in such a way that a free contact surface 44 remains on the field-grading element 22. The area of the contact surface 44 not covered by the insulating sleeve 70 adjoins the air gap 101 or the other adjacent boundary surfaces of the receiving device 12 and the pressure sleeve 62. The pressure sleeve 62 can be made of an insulating material.The embodiment according to the invention with attached or inserted control elements shows a significant improvement over the prior art. In particular, the field elevation in the air gaps shown was effectively suppressed under DC stress, while the existing charge activities were effectively attenuated. Accordingly, the use of field-grading elements has successfully reduced the local field stresses in air gaps and at air / insulating material boundary surfaces.
Claims
1. Plug-in device (10) for detachable insertion into a receiving device (12) for establishing an electrical connection between a high-voltage direct current cable (16) and a high-voltage equipment,having an insulating body (18) which at least partially surrounds the high-voltage direct-current cable (16),characterized inthat the insulating body (18) has a boundary surface (42) along its outer side and a field-grading element (20, 22) made of conductive material is provided at a respective end region of the boundary surface (42), which field-grading elements delimit the boundary surface (42), andthat the one field-grading element (20), which rests on an end face (28) of the insulating body (18) facing the receiving device (12) on the end face (28) of the insulating body (18) as an insert or attachment part (91) or is applied as a coating (88), and in that the second field-grading element (22), which is arranged opposite the one field-grading element (20) on the insulating body (18), is designed as a coating (88) or rests on, rests against and / or is introduced as an insert or attachment part (90, 92).
2. Plug-in device (10) according to claim 1, characterized in that the field-grading elements (20, 22) each have an outer circumferential surface (43) which merges flush into the boundary surface (42) of the insulating body (18) and each have a contact surface (44) outside the boundary surface (42) which merges into the outer circumferential surface (43) or adjoins it. 3. Plug-in device (10) according to claim 1, characterized in that the respective field-grading element (20, 22) is at least mounted or inserted on the insulating body (18). 4. Plug-in device (10) according to claim 3, characterized in that the respective field-grading element (20, 22) is in the form of a coating (88) or in the form of an insert or attachment part (90, 91, 92). 5. Plug-in device (10) according to claim 4, characterized in that the respective insert or attachment part (90, 91, 92) is formed from elastically flexible, conductive elastomer, such as silicone rubber or ethylene-propylene-diene rubber. 6. Plug-in device (10) according to claim 5, characterized in that the respective insert or attachment part (90, 91, 92) consists of the same base material as the insulating body (18). 7. Plug-in device (10) according to claim 4, characterized in that the coating (88) consists of a conductive dispersion or of a conductive paint which is applied as a spray coating or by hand with a brush to the insulating body (18) . 8. Plug-in device (10) according to claim 7, characterized in that the coating (88) consists of a conductive dispersion or of a conductive paint which is applied as a spray coating or by hand with a brush to the insulating body (18) in a circumferential recess (86) thereof. 9. Plug-in device (10) according to claim 4, characterized in that the respective insert or attachment part (90, 91) is designed as a closed annular body which comprises the high-voltage direct current cable (16), or in that the respective insert or attachment part (92) is designed as a closed annular body and an ground deflector (48) is integrated. 10. Plug-in device (10) according to claim 1, characterized in that the insulating body (18) has at least one truncated cone (36, 38, 40) which comprises at least one bending line (32, 34) on the circumferential side, the bending line (32) arranged at a distance from the end face (28) of the insulating body (18) separating the boundary surface (42) from further sections of the truncated cone. 11. Plug-in device (10) according to claim 2, characterized in that the respective field-grading element (20, 22) has an outer circumferential surface (43) and a contact surface (44) which, viewed in cross-section with respect to the longitudinal axis of the insulating body (18), are formed at an angle to one another, or which merge into one another in an arcuate manner, or which are formed in a polygonal manner. 12. Plug-in device (10) according to claim 1, characterized in that a contact system (50) is arranged adjacent to the insulating body (18) and pointing in the insertion direction towards the receiving device (12), which consists at least of a contact ring (52) and a tension cone (54), wherein a thrust piece (56) is arranged between the tension cone (54) and an end face (28) of the insulating body (18). 13. Plug-in device (10) according to claim 12, characterized in that, the thrust piece (56) has a metallic energy storage element (59), by means of which the thrust piece (56) is held in contact with the field-grading element (20) in order to maintain an electrical connection. 14. Plug-in device (10) according to claim 1, characterized in that a pressure sleeve (62) is provided, which bears against the insulating body (18) in the opposite direction to the direction of insertion into the receiving device (12) and has a pressing surface (63), which bears directly or indirectly against the contact surface (44) of the further field-grading element (22). 15. Plug-in device (10) according to claim 14, characterized in that the pressure sleeve (62) presses the insulating body (18) into the receiving device (12) with an energy storage element (64) via the contact surface (44) of the further field-grading element (22). 16. Plug-in device (10) according to claim 14, characterized in that- an insulating sleeve (70) is provided, which extends from a bell flange (72) surrounding the high-voltage direct-current cable (16) in the direction of the insulating body (18) and an end section (71) of the insulating sleeve (70) overlaps the contact surface (44) of the further field-grading element (22) in the form of the coating (88) or the insert or attachment part (90) and only partially covers the latter, or - the end section (71) of the insulating sleeve (70) lies against a bending surface (33) of the insulating body (18) at a distance from the contact surface (44) of the further field-grading element (22) in the form of the coating (88) or the insert or attachment part (90), or- the end section (71) of the insulating sleeve (70), starting from the bell flange (72), extends at least between the pressing surface (63) of the pressure sleeve (62) and the contact surface (44) of the further field-grading element (22) in the form of the insert or attachment part (92), but does not completely overlap the contact surface (44). 17. Plug-in connection assembly (14) having a plug-in device (10) according to claim 1, which is designed in the manner of a plug and interacts with the receiving device (12) in the manner of a socket (78), which is coupable to one another by means of a flange connection (74, 76),characterized in that- in the coupable arrangement of the plug-in device (10) in the receiving device (12), the field-grading elements (20, 22) and the boundary surface (42) of the insulating body (18) arranged therebetween and the outer circumferential surface (43) of the field-grading elements (20, 22) bear against a contact surface (26) of the receiving device (12), and further boundary surfaces of the plug-in device (10) and the receiving device (12) are assigned to one another outside the field-grading elements (20, 22) in each case, these further boundary surfaces bearing against one another or at least one air gap (100, 101) being formed therebetween, and- the field-grading elements (20, 22) reduce the local electric field stresses at the boundary surfaces or in the at least one air gap (100, 101) to a level such that the electric strengths of the at least one air gap (100, 101) and their further boundary surfaces of the plug-in device (10) and the receiving device (12) are prevented from being exceeded. 18. Plug-in connection assembly (14) according to claim 17, characterized in that a pressure sleeve (62) is present on the plug-in device (10), which presses the boundary surface (42) of the insulating body (18) flat against the conical contact surface (26) of a socket (78) of the receiving device (12) by means of a spring assembly (64).
19. Plug-in connection assembly (14) according to claim 17, characterized in that at least one electrode (82, 84) is provided in the socket (78), the one electrode (84) being assigned to a contact socket (60) and being electrically connected to the latter, and in that the outer circumferential surface (43) of the field-grading element (20) does not exceed the height of the metallic electrode (84), and if a further electrode (82) is provided in the socket (78), which is positioned at a distance from the first electrode (84) and lies at an earth potential, the outer circumferential surface (43) of the further field-grading element (22) does not exceed the height of the electrode (82).
20. Plug-in connection assembly (14) according to claim 17, characterized in that a bell flange (72) is arranged on the side facing away from the insulating body (18), which bell flange has a flange part (74) for establishing the flange connection with a further flange part (76) of the socket (78).