Abstract:
An outdoor terminal is mounted at one end on a pylon. A base armature is provided fastened to a cable with an electrical feedthrough to the interior of the terminal. The cable terminal is electrically connected to a ground potential and includes a field control element and isolations at inhomogeneous potential transitions on the cable end. The electrical feedthrough is configured as a tube or a pin and is connected to the cable conductor via contract elements. The feedthrough, the insulators and the head armature form one assembly unit.

Description:
FIELD OF THE INVENTION 
     The invention relates to a cable terminator, preferably an outdoor terminator for high voltage. 
     BACKGROUND OF THE INVENTION 
     Various types of terminators are known. Older designs are formed with porcelain insulators and an oil or other chemical filling. Such terminators have the disadvantage that they are not very robust mechanically, and no longer fulfil present-day environmental protection conditions with regard to possible substance leakage. A terminator without oil filling is described in EP 667 665 B1. A special feature of this terminator is a rigid conducting element which is designed to take up the lateral forces. The forces are carried awayfrom the overhead conductor connection via the rigid conducting element, via a base body with a field control and insulating device, to the bearing structure. The weak point of this arrangement is the transition tram the conducting, rigid element to the base body. 
     An object of the invention is to propose a cable terminator, preferably a high-voltage outdoor terminator, which can be produced at low cost, is mechanically stable and entirely satisfies the mechanical requirements. 
     SUMMARY OF THE INVENTION 
     A terminator is mounted at one end on a base fitting, preferably for fastening to a cross-arm. Means for fastening the cable are formed on the base fitting and have an electrical duct tube or pin inside the terminator. Situated at a top fitting are means for fastening to the pin. Means for electrically connecting the cable shield to ground potential and means for the field control and insulation at the inhomogeneous potential transitions at the cable end are present. 
     The insulating body generally bears on its surface an elastomeric material (preferably of silicone rubber) with a ribbed surface (shielding plates). The length and in particular diameter of the insulating body is to be chosen such that the demands for sufficient insulation and avoidance of atmospheric flashovers at full operating voltage are met. This requirement can be fulfilled by covering the surface of the insulating body with a resistive or refractive control coating. 
     The insulating body is fastened to the base fitting. The further, customary means for electrically connecting the cable shield to ground potential and means for the field control (field control bodies) and insulation at the inhomogeneous potential transitions at the cable end are employed. On the fastening to the base fitting, voids present between the cable end and the field control and insulating elements are closed by mechanical bracing with the base fitting. 
     The insulating body is filled up with material from the region of the fastening to the base fitting up to the level of the contact elements, and that the filling is reduced towards the top fitting, with the result that an internal cavity is formed. 
     The three parts consisting of electrical duct with contact elements, insulating body and top fitting are produced separately. The top fitting consists essentially of an electrically conductive end plate and an overhead conductor connection piece, in which a thread may be incorporated for the fastening of a carrying lug. The electrical duct, designed as a tube or as a pin, is preferably fastened inside the end plate in a welding operation (or by another firm mechanical connection). The insulating body, consisting of insulating material, is bonded into the top fitting. The unit, also referred to as assembly unit, is lifted by a crane at a carrying lug into the assembly position and lowered from above over the prepared lower part of the terminator. The dimensions of the parts in the lower region of the assembly unit are designed such that upon assembly they slide in a self-centering manner into the base structure on the base fitting. In the process, the electrical duct also comes into contact with the cable conductor via contact elements. 
     A cable plug system is preferably employed for the contact receptacle; the latter may be fastened to the cable conductor with screws. The electrical contact to the electrical duct is provided by contact laminations. This plug connection is not designed to take up the forces on the terminator. In the present arrangement, the insulating body is therefore constructed and dimensioned so as to be able to take up all the mechanical forces. The plug relieved of mechanical loads. A typical magnitude of the transverse force to be expected is 5 kN, so that the mechanical design is to be dimensioned for this characteristic quantity. 
     The insulating body is produced from cast resin or another suitable material. It may be materially strengthened, for example with glass fibers. The insulating body is completely filled up with material from the bottom edge up to the level of the contact elements. A cavity is preferably formed in the interior of the insulating body. The cross-section of the cavity (the space filling) may be linear or be reduced in a curve in the shape of a tunnel towards the top fitting. The form of the cavity allows the weight to be kept low, the wall thickness may not be reduced further than a point where the bending forces can be taken up. In a preferred design, the inner surface of the cavity is lined with a conductive coating. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the outdoor terminator are illustrated in the figures, in which, specifically: 
     FIG. 1 shows a first embodiment with constant outside diameter; 
     FIG. 2 shows another embodiment with stepped outside diameter; 
     FIG. 3 shows an embodiment with different external contours in the right-handed and left-hand half of the figure; and 
     FIG. 4 shows two flange designs. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The terminator according to the invention—for example for a rated voltage of 145 kV and having a conductor cross-section of 1200 mm 2 -comprises an insulating body  50 , preferably made of cast resin, which has a cavity  56  in its interior. In the lower region  51 , it can be seen that at the end of the cable core (conductor  12  and conductor insulation  15 ) the arrangement of the field control element  36  and insulating by  50  is designed in accordance with the structure known to a person skilled in the art. 
     The field control body  33  consists of silicone rubber and its control element  36  lies on the transition region between the conductor insulation  14  and the end of the conductive layer  15 . The insulating body  50  has a cylindrical external profile. The insulating body  50  has, in the upper region, a constant outside diameter over its length. In the lower region  51 , it accommodates the field control body  33  and is screwed onto the base part  20 -flange  20 ′. A cavity  56 , the inner surface  54  of which is designed to be electrically conductive, is formed in the upper region of the insulating body  50 , in its interior. Admission of air to the cavity  56  is possible. 
     The insulating body  50  is screwed, in the base part having a base plate or a flange  20 ′, onto a supporting frame  29 , for example a cross-arm, via insulating supports  21 . Alternatively, the lower region  51  of the insulating body  50  may also be formed as a cast body which fits in mating fashion into the flange  20 ′. 
     A high-voltage cable  10  is led into the lower region of the outdoor terminator  8 . The shielding wires  11  of the cable  10  are in electrical contact with the flange  20 ′ of the base part  20 , which is mounted via insulators  21  on a arm  29  of a pylon. 
     As mentioned, the diameter of the insulating body  50 , in particular in the lower region  51  (see also reference numeral  53  in FIG.  3 ), is dimension such that the external field strength in all operating states is below critical values. Owing to the installation of the field control elements  36 , a relatively large diameter is required. However, the diameter above the field control region may be reduced. But this presupposes that the shielding plates  62  follow the conical or stepped contour. The forming costs for shielding plates  62  with a contour which varies over its length are high, however, so that an arrangement with a constant cross-section over the entire length of the insulating body  50  is preferred. 
     As shown in FIG. 2, for example, the insulating body  50  may consisting of two parts ( 51 ′,  51 ″) bonded together and with different material qualities. The lower part  51 ″ (fastening to the base fitting up to the level of the contact elements on the cable conductor) is -without being covered with shielding plates  62 —exposed to the environment; this part must be suitable for outdoor use. The part  51 ′ may consist of a simple material, since this region is always covered with shielding plates  62 . For an embodiment such as in FIG. 3 having shield plates  62 . 1  down to the base fitting, there is likewise an outer protective covering, so that a simple material quality of the insulating body  50  may b employed for this region too. 
     The external contour  59  of the insulating body is preferably cylindrical over the entire length. It is covered with shields  62  made of RTV or LSR silicone rubber. The outer surface under the shields  62  may preferably be covered with a field-controlling coating  64 . Depending on the form, quality and presence of this coating  64 , the insulating body  50  may be designed with different diameters (greater at the bottom and decreasing at the top and a conical transition therebetween) (see FIGS.  2  and  3 ). The coating  64  may be applied in varying thicknesses for an optimum controlling effect. 
     The inner surface  54  of the cavity  56  may be designed to be conductive. It may be produced by conductive lacquer, conductive plasma coating, metal foil (sheet), metallization or metallic cloth embedded in resin. The surface  54  is at high-voltage potential. The advantage of this design is that, even in the event of condensation of water in the cavity  56 , the electrical reliability remains guaranteed, since the electrical field conditions are uniform given the high-voltage potential present. 
     The contact  17 , embedded in the cast-resin body  50 , embraces the end contact  30  at the lower end of the tube or pin  32  capable of carrying current. The pin  32  runs up to the top fitting  70  and is fastened there. A mechanically and electrically leaktight end cover  71  is fitted in the upper region of the terminator  8 . 
     The connection between cable conductor  12  and electrically conductive pin  32  is arranged at the transition from the full-volume base body in the lower region  53  to the cavity  56 . The connector  30  clamps the uncovered cable conductor  12  in the lower part. The current flows from the cable conductor  12  via the contact  17  to the pin  32 . For this purpose, slidable contact or clamping elements are preferably provided between cable conductor  12  and electrical pin  32 . The transition between connector  30  and contact laminations  42  may be sealed by means of an O-ring. 
     In the right-hand half of FIG. 3 there is an embodiment of the insulating body  50  having a slightly convex thickening in the lower region  53 . The metal ring  26 , used for ground connection, can still be used in this design with an unchanged diameter. Shielding plates  62 . 1 ,  62 . 2  may be present in the convex region  53 . 
     The two FIGS. 4A and 4B show different forms of a flange  20 ′,  20 ″. The fastening the insulating body  50  to the flange  20 ′,  20 ″ is effected using a plurality of screw connections  23  (FIG.  2  and FIG.  3 ). By tightening the screws  23 , assembly unit mentioned is braced via the spring elements  44  (see FIG.  3 ), so that voids present in the region of the field control body  33  are completely closed. Reference numeral  24  (FIG. 3) indicates a conductive connection of the surface of the insulating body  50 , adapted for ground connection, to the cross-arm  29 . Attached to the foot of the insulating body  50  is a metal ring  26 . The metal ring  26  is brought into contact with the ground conductive connection  24  (see FIG. 3) via a screw  23 .