A coupling is used with a U-section longitudinally extending power track having a floor and a pair of side walls defining a longitudinally and transversely open retaining channel and provided on the side walls with respective dielectric support rails each carrying a respective longitudinally extending main conductor transversely exposed in the slot and connected to phase or ground. The coupling has a dielectric coupling housing extending along an axis and having center structure defining a center symmetry plane perpendicular to the axis and end formations projecting axially oppositely from the center structure and each fittable longitudinally into the channel at an end of the power track to an insertion depth determined by the center structure. Two L-section and longitudinally extending metallic contact strips are carried on and transversely limitedly movable in a predetermined transverse direction in the dielectric housing.