| 摘要 |
PROBLEM TO BE SOLVED: To prevent the dielectric breakdown of a distribution board and a relay, and to avoid the impossibility of communication from a base station, even if a distribution line receives a thunder stroke. SOLUTION: When the distribution line 12 receives the thunder stroke, an overvoltage is applied to an SPD 1 connected to a primary winding of step-down transformer 24 by a thunder current, the primary winding and the grounding pole 26 are short-circuited, the thunder current flows to the grounding pole 26, one end of an SPD 2 has high potential by grounding resistance, the primary and secondary windings of the step-down transformer 24 are short-circuited by the SPD 1 and the SPD 2, and thus the dielectric breakdown is prevented. Furthermore, the thunder current flows in a relay power cable 22, an overvoltage is applied to an SPD 3, the relay power cable 22 and a shield of the communication line 18 are short-circuited by equal potential bonding 28, overvoltages are applied to an SPD 4 and an SPD 5, a shield of a communication line 18 and its core wire are short-circuited, the thunder currents flow to the shield of the communication line 18 and its core wire, and thus the breakage of the relay 20 can be prevented. COPYRIGHT: (C)2008,JPO&INPIT
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