PURPOSE: To interrupt and protect a power receiving circuit upon occurrence of natural disaster, while preventing the secondary disaster such as fire, by interrupting power supply to a load circuit when the circuit voltage is lower than a decision level at the time of resuming power supply or when the resistance of the load circuit is significantly low.
CONSTITUTION: When power supply to a power receiving circuit is resumed after temporary interruption or when the power supply voltage drops abruptly although power supply is not interrupted, it is decided whether the circuit voltage (voltage at a part closer to the load than a WHM 3, e.g. a voltage being applied to a main circuit breaker 5) is lower than a decision level (e.g. a voltage 20V lower than a standard voltage 100V under steady state). If the circuit voltage is lower than the decision level, power supply to a load circuit 7 is interrupted. Alternatively, the resistance of the load circuit 7 is measured upon occurrence of power interruption and if the resistance is significantly lower than a decision reference value (e.g. about 200kΩ), power supply to a load circuit 7 is interrupted.
FUJIWARA MASAHIKO
ONUMA TOSHIO
HAYASHI HIDEOMI
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