S. W. WAN ET AL. 1157
while helicopter is in a high field region, and it is harm-
ful to inspection persons. Th e electric field near the cabin
window is not completely shielded by the helicopter air-
frame, but decreases very fast at the middle cabin.
Through the critical discharge energy for person, the
safety distance is determined as d≥15m, and it has been
well adopted in power grid already.
6. Acknowledgements
The authors acknowledge financial support from the key
Project of National Basic Research Program of China
(2009CB724503)
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