Influence of the Assembly Method of Medium Voltage Mechanical Connectors on the Quality of the Electrical Connection

Power cables are connected with ferrules or lugs in the area of high, medium and low voltage. Nowadays, there are two main installing techniques, which are state of the art: compression or crimping and bolted mechanical connections. The bolted mechanical connectors are installed by hand with the use of a mechanical wrench. The customer demand of using impact wrenches (IW) is growing because of the higher installation comfort. However, these techniques differ from each other significantly as the quality of the connection depends on the screwing force applied by the bolt to the conductor. Therefore, a new approach by using a cordless screwdriver was investigated. This contribution addresses the topic of the quality of the electrical connection as a function of the assembly method used on mechanical connectors. In particular, the focus is on assembly by hand with the support of mechanical wrenches and assembly with impact wrenches. Furthermore, a method is presented that combines the advantages of both methods, whereby the disadvantages are eliminated. This involves the use of an adapter, the torque amplifier, which is part of the installation philosophy of Nexans Power Accessories. First, the fundamentals as well as the current state of the art of connection technology are presented. This is followed by a description of the assembly methods and materials used in this work and a comparison of the electrical, mechanical and thermal properties according to IEC 61238 of the connection using the different assembly techniques. Finally, the advantages and disadvantages are compared and presented and discussed using tabular and graphical representations.