| 摘要 |
PROBLEM TO BE SOLVED: To cut off a wiring route instantaneously when a discharge-type short circuit such as a short circuit between cord conductors, a tracking short circuit, etc., occurs while the wiring route is not cut off when an overflow current or a rush current is applied. SOLUTION: A current transformer 2 which detects a wiring route current, a filter circuit 3 which extracts a commercial frequency component from the current detected by the current transformer 2, a peak value conversion circuit 6 which detects the peak value of the extracted commercial frequency component and holds the peak value, a peak detection circuit 7 which detects the peak value of the current containing a discharge-type short circuit current from the current detected by the current transformer 2, and a comparison circuit 8 which outputs the operation signal of a thyristor drive circuit 9 when the output of the peak detection circuit 7 exceeds a threshold which is the output of the peak value conversion circuit 6 are provided. When a thyristor 10 is turned on, a trip coil 11 is made to operate to open contact devices 13.
|
