A fuse for an alternating current ppower circuit. The fuse comprises an input terminal (4), a first contact (5) electrically connected to the input terminal, an output terminal (9) and a second contact (8) electrically connected to the output terminal. A fusible element (11) electrically connects the first and second contacts and completes a normal electrical path between the input and output terminals. An arcing contact (6) is positioned in relation to the first contact (5) so as to form a potential arc path between the first contact and the arcing contact, along which path an arc will become established after the fusible element breaks in response to fault current. The arcing contact (6) is electrically connected to a third terminal (41) and is electrically isolated from the output terminal (9). The fuse can be used in a single phase circuit to reduce let-through energy to a load under fault conditions, or in each phase of a multi-phase circuit to break the supply to all phases in response to a fault on any one phase.