Numerical Study of Lightning-Induced Currents on Buried Cables and Shield Wire Protection Method

In this paper, the two-step finite-difference time-domain method of solving full-wave Maxwell's equations is adopted to analyze the lightning electromagnetic pulse (LEMP) coupling to buried cables. The influences of lightning strike point, cable length, and ground conductivity on the LEMP coupling to buried cable are evaluated. The method of using shield wires to decrease the lightning-induced currents on the buried cables is proposed, and the protection efficiencies of different installing ways of the shield wires are evaluated. The numerical results show that when the lightning strike point is in the axial direction of the cable, the coupling is rather strong; the induced current acutely increases as the lightning strike point approaches the cable; when the length of the cable does not exceed about 150 m, the induced currents at the cable ends increase as the length increases, whereas once the length of the cable exceeds 150 m, the induced currents begin to decrease; the shield wires can effectively decrease the lightning-induced currents on the buried cables, closer the shield wire, greater the protection efficiency, and more shield wires provide greater protection efficiency.