| 摘要 |
PROBLEM TO BE SOLVED: To prevent such a trouble that a thunder attack detecting circuit is switched into its initial state by a power failure thereby determining that there is no approach of thunder and switching a protected device to a normal state at the continuation of thunder approach. SOLUTION: This lightning stroke protective device is equipped with the thunder attack detecting circuit which determines the existence of thunder approach by detecting a thunder signal, and a switching mechanism which switches the protected device into the normal state where it is connected to an electric path and a thunder-resistant state where it is cut off the electric path. The lightning stroke protective device is switched to the normal state at normality by the signal from the thunder attach detecting circuit and to the thunder-resistant state at the approach of thunder by means of the switching mechanism, getting control power from a low-voltage power line. The device determines the existence of thunder approach for a specified time after the recovery of control power in the case that the control power has failed, and it switches the protected device to the thunder-resistant state at the existence of the thunder approach, and to the normal state at the presence of the thunder approach. COPYRIGHT: (C)2005,JPO&NCIPI
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