Patent ID: 8189307

Claim:
A composite type electric circuit breaking method, comprising the steps of: (a) detecting an arc signal, an overcurrent signal, and an earth leakage signal, respectively; and (b) counting the number of detected arc signals, and compositely interpreting the respective arc, overcurrent, and earth leakage signals detected at each point in time of a number of decision points in time, according to a predetermined interruption condition, to thereby grasp association of the respectively detected arc, overcurrent, and earth leakage signals, and to thus interrupt an electric power supply, wherein the electric power supply interruption step (b) comprises the sub-steps of: (b1) if a present point in time is a first decision point in time at which predetermined time has passed from an arc generated point in time, judging whether or not an arc signal is generated according to whether or not a present electric current value is at an overcurrent mode, when the number of counted arc signals is not less than a predetermined number of times and electric current is changed; (b2) if it is judged that no arc signals have been generated at the first decision point in time, cumulatively counting the number of arc signals generated from the first decision point in time to a second decision point in time at which predetermined time has passed from the first decision point in time, and judging whether or not the generated arc signals are considered as arc signals according to whether or not the present electric current value is not less than a rating electric current value, when the number of the cumulatively counted arc signals is not less than a predetermined number of times and electric current is changed; (b3) if it is judged that no arc signals have been generated at the second decision point in time, cumulatively counting the number of arc signals generated from the second decision point in time to a third decision point in time at which predetermined time has passed from the second decision point in time, and judging whether or not the generated arc signals are considered as arc signals according to whether or not the present electric current value is not less than a predetermined value, when the number of the cumulatively counted arc signals is not less than a predetermined number of times and electric current is changed; and (b4) if it is judged that no arc signals have been generated at the third decision point in time, cumulatively counting the number of arc signals generated from the third decision point in time to a fourth decision point in time at which predetermined time has passed from the third decision point in time, and judging whether or not the generated arc signals are considered as arc signals according to whether or not the present electric current value is not less than a predetermined value, when the number of the cumulatively counted arc signals is not less than a predetermined number of times and electric current is changed.