Abstract: An elongated, insulative tube of high mechanical strength consists of resin bonded glass fibers wound in alternating helical and circumferential winding patterns. The glass fiber convolutions at the outer limits of these winding patterns embrace metallic inserts, securely captivating them within the open ends of the tube. Tapped central bores in these inserts threadedly receive end fittings adapting the tube to a transmission line supporting function. The tube also externally mounts a pair of spaced arcing rings and internally mounts a varistor array for protecting a transmission line against lightning strikes.

Abstract: An elongated, insulative tube of high mechanical strength is equipped with fittings at each end for electrical connection with a high voltage transmission line and a grounded tower. An external spark gap is provided between a first arcing ring mounted in electrical connection with one end fitting and a second arcing ring mounted to the tube intermediate its ends and electrically connected with a contact member disposed within the tube. The portion of the tube interior between the contact member and the other end fitting is packed with a series array of varistor discs. The tube maintains the line in spaced relation with the tower, while the varistor array and spark gap absorb voltage surge differentials between the line and tower.