| 摘要 |
PROBLEM TO BE SOLVED: To provide a surge protection device for preventing interruption of power supply to a protection target device due to failure of an SPD by allowing an SPD separator to operate earlier than an input breaker of the protection target device, irrespective of the state (resistance value) of the SPD in failure when the SPD is deteriorated and in a failure. SOLUTION: A voltage to be applied to a broken SPD 1-1 when the failure occurs in the SPD 1-1 is about the commercial power supply voltage, so that switching type SPDs (gas-encapsulated discharge tube type SPDs etc.) 6-1, 6-2, 6-3 and the other two normal SPDs 1-2, 1-3 are in an insulation state. Accordingly, a short circuit current of the SPD1-1 flows to a ground line 4-1 through an additional resistance 7-1. The short circuit current is suppressed in failure of the SPD, so that the SPD separator 2-1 is interrupted earlier than the input breaker 3. Thus, the broken SPD 1-1 can be separated from a power feeding system without causing influence on the protection target device 10, irrespective of the state of deterioration (resistance value) of the SPD 1-1. COPYRIGHT: (C)2010,JPO&INPIT
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