stress over some length of the lead wire 2 thus providing strain relief and robustness against vibrations returning momentarily to fig1 a it will be appreciated that many of the fastening elements in fig1 a including the bolt 15 and the nut 17 rely on tensile strengths and thus force the use of materials with high tensile strengths likewise the fastening element of crimp terminal 14 relies upon a persistent crimp connection due to swaging of material of the crimp connection also calling for high tensile strength of portions of the material of the crimp connector returning momentarily to fig1 b it will be appreciated that the connection point 12 is likewise required to be strong against separation which calls for tensile strength of materials and surface junctions resilient and elastic materials such as plastics with smaller tensile strengths than metals are not well suited to the approaches of fig1 a and 1 b in contrast in the approach of fig6 the plug 3 that is performing the role of a fastener relies on compressive strength rather than tensile strength this permits the utilization of materials such as non conductive plastics that traditional intuition would have ruled out from a robust mechanical design such as in fig1 a or 1 b the resilience of the plug 3 provides for continuous application of the clamping force even when the dimensions of the hole 6 and of the lead wire 2 change due to the changing temperature of the shunt bus bar 1 stated differently expansion and contraction of the rigid parts in fig3 e are not problematic because the.