EXPERIMENTAL STUDY ON LIGHTNING STRIKE RESISTANCE PERFORMANCE OF ONE KIND OF TETHER CABLE

摘要

The lightning strike resistance performance of one kind of tether cable (or mooring cable) used in field of tethered balloon was experimentally studied. As the mooring rope of tethered balloon, the tether cable stands on the ground up to several kilometers, unavoidably could be struck by lightning. In order to ensure its mooring and other functions (such as providing power and communication, etc.), the design of tether cable should meet the safety requirements of lightning protection. The outer layer of the researched tether cable is designed to conducting lightning current through woven copper mesh embedded in outer insulation sheath. The interlayer manufactured by aramid fiber is intended to use as strained layer to sustain tension. It is the core wire presenting power and communication which should be protected. Because the tether cable has probability to be struck directly, the lightning strike resistance performance should be verified by the large current arc injection testing, and mooring tension should also be applied on the cable to simulate the mooring load when performing the test. Also, to fully investigate the mechanical shock and thermal ablation effect of lightning strike, combined lightning environment made of current component A and C ought to be continuously applied. Based on the arc injection method recommended in the SAE ARP5416 standard, the discharging loop structure which can force tons of tension was designed for the lightning strike testing of the tether cable. In accordance with SAE ARP5412, the lightning strike testing was conducted by applying component A with action integral of 2 × 10~6 A s and component C with charge transfer of 200 C, and applying tension with weight of 2 tons. After lightning strike testing, although local penetration of outer sheath, local ablation of copper mesh in current conducting layer and local surface carbonization of aramid layer were found, the tether cable was not broken under forced and the internal core was also not affected and perform normally. Thus the design of the tether cable can meet the lightning protection requirements of tethered balloon.