Recent years have seen different manufacturers introduce interesting design innovations when it comes to straight joints for medium voltage cables. In most cases, the principal advantage of these innovations – all more or less in a single joint – is reduction in the number of different components. There is also integration of a particular mechanical connector into the joint insulation to help minimize serious errors during installation. A good first example of these is a new cold shrink joint having an integrated plug in and shear bolt connector combination (see photo). The entire connector consists of a hull embedded in the middle of the insulation body as well as two plug elements to be fixed onto the cable ends with two shear bolts. The joint insulation is positioned on the middle of the connector hull and expanded at both ends by spirals as a cold shrink solution. Installation of such a joint is also easy. After cable preparation, both plug elements are fixed on the cable conductors by two bolts. The cable ends have to be inserts into the insulation body and in the connector hull. Snap rings on both sides prevent this connection from ever becoming unplugged.
Another new joint has a special connector without the need to use any bolts. Numerous lamella or blade contact elements provide for transmission of current. In the case of different conductor diameters, an adaptive retaining device interlocks the conductors in the connector. This special connector solution is for different MV cable cross-sections but only suitable for solid conductors. The medium voltage insulation of the two joints is normal radial silicone insulation with an inner semi-conductive layer, an insulation layer and an outer semi-conductive layer.
Yet another but totally different innovation is the insulation body of a compact joint being offered by a different supplier. In this case, the connector is a more-or-less standard shear bolt connector but the insulation body is unique in medium voltage insulation design. Apart from two openings for the cable ends, it has four additional openings as well for the connector bolts. As with other innovative designs, installation is also easy. After cable preparation, the cable ends have to be inserted into the insulation body. The connection is made by tightening and shearing the bolts. Then, it is only necessary to close the bolt openings in the insulation by means of a special insulation plug.