A combined ground fault and arc fault circuit interrupter includes a differential current transformer, a hot electrical line and a neutral electrical line passing through the current transformer and forming the primary thereof, an asymmetrical current transformer having a core through which the hot and common electrical leads pass, and a secondary wound on the core for producing a signal more strongly responsive to the current in the common line than in the hot line. An arc fault detector is connected to the secondary of the second transformer, while a ground fault detector is connected to the secondary of the first transformer, and the outputs of the ground fault and arc fault detectors are both connected to a circuit interrupter arranged for disconnecting the circuit when either a ground fault or an arc fault is detected.