| CPC H02H 3/331 (2013.01) [H01H 83/144 (2013.01)] | 17 Claims |

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1. A ground fault circuit interrupter (GFCI), comprising:
a first current transformer (CT) comprising:
a first core, wherein the first core is a PCB core or an air core; and
a ground fault (GF) sense winding wound around the first core;
a second CT comprising:
a second core, wherein the second core is a ferromagnetic or nanocrystalline core; and
a grounded neutral (GN) sense winding wound around the second core;
a GF detection module operatively connected to the GF sense winding to receive signals from the GF sense winding and configured to determine whether a line-to-ground fault exists; and
a GN detection module operatively connected to the GN sense winding and configured to receive signals from the GN sense winding to determine whether a neutral-to-ground fault exists;
wherein the first CT includes a test winding wrapped around the first core, wherein the GF sense winding winds around a greater portion of the first core than does the test winding.
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