Electrical power cable adaptor and method of use

#The present invention relates generally to electrical stress control in electrical power cables, and more particularly to an article and method for controlling electrical stress in a region of high electric field strength associated with electrical power cables and their associated accessories.

#As used herein, “high voltage” generally refers to voltages sufficiently high to cause breakdown of the cable insulation at cable shield discontinuities. Without limiting the scope of the present invention, in some implementations, “high voltage” generally refers to voltages of 50 kV or greater, although the present invention is also beneficially used with lower voltages.

#A typical high voltage cable includes a central electrical conductor, a semiconducting layer (also referred to herein as a conductor shield) surrounding the electrical conductor, an electrically insulating layer covering the conductor shield, and a semiconducting layer (also referred to herein as an insulation shield) over the insulating layer. In terminating such a cable, it is customary to remove or cut back each successive layer of the cable to expose the layer below. Cutting back the semi-conductive cable shields causes a discontinuity in the cable electric field, resulting in high electric stress at the cut ends of the shields. The high electrical stress can cause electrical discharges to occur, which in turn tends to cause breakdown of the insulating layer of the cable.

#Embodiments of the invention are better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

#FIG. 1 is an illustration of an electrical power cable prepared for installation of a stress control adaptor according to the invention.

#FIG. 2A is a cross-sectional illustration of one embodiment of a stress control adapter according to the invention.

#In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. The illustrated embodiments are not intended to be exhaustive of all embodiments according to the invention. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. For example, while the present invention is primarily described in connection with a termination of a cable, it is suitable for employment with high voltage cable joints and other high voltage equipment including electrical bushings and feedthroughs. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

#Referring to FIG. 1, an exemplary power cable 10 is illustrated. Exemplary power cable 10 includes a central electrical conductor 12, a semiconducting layer 14 (also referred to herein as conductor shield 14) surrounding electrical conductor 12, a layer of electrical insulation 16 covering conductor shield 14, and a semiconducting layer 18 (also referred to herein as insulation shield 18) over insulation 16. Insulation 16 may comprise a material such as crosslinked polyethylene (XLPE), polyethylene (PE), or ethylene propylene rubber (EPR), or other materials as are known in the art. Additional protective layers (not shown) may additionally be provided over insulation shield 18.

#As described herein electrical insulation 16 of cable 10 is understood to have a reduced thickness that, absent supplemental electrical stress controlling measures, requires use of a cable accessory in a higher voltage class than the cable voltage class (e.g., using a cable accessory rated for 138 kV with a 110 kV cable having reduced insulation thickness). Such a cable having reduced-insulation thickness may be referred to herein as a thin-walled cable. In contrast, a cable having electrical insulation sufficiently thick to allow use of a cable accessory in the same voltage class as the cable voltage class, without the use of supplemental electrical stress controlling measures, is referred to herein as a standard cable.