抄録
The transient behavior of an earth-wired tower struck by a vertical lightning stroke, which was computed by NEC-2, is characterized for modeling. A tower struck by a lightning stroke behaves as an antenna until a traveling wave makes several round-trips in the tower. During this interval, the tower footing impedance appears to be higher than the footing resistance, and the coupling coefficient between the earth wire and a phase conductor is much lower than that in the TEM mode. A new procedure to determine the circuit parameters of the multistory tower model for the EMTP multi-conductor analysis, on the basis of the measured or computed insulator voltages, is proposed. The proposed model can reproduce the insulator voltages computed by NEC-2 reasonably well. The surge impedance of the top of the proposed tower model is 200 Ω for a typical double-circuit tower equipped with an earth wire.
