Patent ID: 7359167

Claim:
A leakage-current detection and interruption apparatus for a load, said apparatus comprising: a plug adapted to receive an alternating current voltage; at least one pair of separable contacts adapted to receive said alternating current voltage from said plug; an operating mechanism adapted to open and close said separable contacts; a cord comprising two power conductors adapted to electrically conduct said alternating current voltage from said separable contacts to said load, and two non-load carrying, non-ground conductors at least one of which does not shield one or both of said power conductors; and a detection circuit adapted to detect a plurality of faults in said cord, said detection circuit comprising a ground fault detection circuit comprising a current transformer including an opening through which said power conductors pass, said ground fault detection circuit cooperating with said two non-load carrying, non-ground conductors to detect at least one of said faults and with said operating mechanism to interrupt said detected faults; wherein said current transformer is a first current transformer disposed within or proximate to said plug; wherein said detection circuit further comprises a second current transformer disposed proximate said first current transformer and a third current transformer disposed proximate said load; wherein said power conductors comprise a line conductor and a neutral conductor; wherein said second and third current transformers include an opening through which said neutral conductor passes; and wherein said first current transformer includes a first secondary winding, said second current transformer includes a second secondary winding electrically connected in parallel with said first secondary winding, and said third current transformer includes a third secondary winding electrically connected in antiparallel with said first secondary winding.