Y.s. Securities Limited

Martin C Oakes

David William Klaus

Graham D Scully

Michael Adams

A three-phase electrical ring main unit comprising a lower chamber module (30) having a wall structure formed from insulating resin material; three input contacts (35), one for each phase, mounted within the lower chamber; three lower switching contacts (37), each mounted within the lower chamber for movement between different switching positions; insulating closure means (55) closing the top of the lower chamber; three output contacts (49), one for each phase, carried by and exposed on a lower face of the closure means; three busbar contacts (59 to 61), each electrically connected to a respective output contact, carried by and exposed on an upper face of the closure member (55); an upper chamber module (31) having a wall structure formed from insulating resin material; means (32) securing the upper chamber above the lower chamber; three tee-off contacts (85), one for each phase, mounted within the upper chamber; and three upper switching contacts (83), each mounted in the upper chamber for movement between different switching positions; one switching position of the lower switching contacts effecting electrical connection between the input contacts and their associated output contacts; and one switching position of the upper switching contacts effecting electrical connection between the busbar contacts and their respective tee-off contacts.

Electrical ring main unit

A fuse for an alternating current power 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.

Alternating current power circuit and fuse therefor

A fuse for an alternating current power circuit in the medium voltage (3.3 kV to 38 kV) range. The fuse comprises a sealed chamber and a first electrode (41) is mounted within the chamber, the first electrode having a substantially circular periphery (42) and being electrically connected to a first terminal (3) to which a first conductor may be connected. A second electrode (35) is arranged with a conductive surface internally of the chamber, the conductive surface being spaced from the first electrode. A coil (10) is connected in an electrical path between the second electrode (35) and a second terminal (18) to which a second conductor may be connected. An additional electrical contact (44) is mounted within the chamber and in direct electrical connection with the second terminal, and a fusible element (43) directly electrically connects the first electrode (41) and the additional electrical contact (44). An electronegative halogenated medium fills free space within the chamber. The normal current path between the first and second terminals and through the fuse is by way of the first electrode (41), the fusible element (43) and the additional electrical contact (44). The arrangement is such that when the fusible element (43) breaks, the resulting fault current forms an arc between the first electrode (41) and the additional contact (44), one root of the arc subsequently commutates from the additional contact (44) to the second electrode (35), the fault current flows through the coil (10) and induces a magnetic field, the magnetic field causes the arc to rotate around the first electrode in the electronegative medium, and the arc is thereby extinguished, so interrupting the fault current.

Fuse for an alternating current power circuit

A fuse for an alternating current power circuit in the medium voltage (3.3 kV to 38 kV) range. The fuse comprises a sealed chamber and a first electrode (41) is mounted within the chamber, the first electrode having a substantially circular periphery (42) and being electrically connected to a first terminal (3) to which a first conductor may be connected. A second electrode (35) is arranged with a conductive surface internally of the chamber, the conductive surface being spaced from the first electrode. A coil (10) is connected in an electrical path between the second electrode (35) and a second terminal (18) to which a second conductor may be connected. An additional electrical contact (44) is mounted within the chamber and in direct electrical connection with the second terminal, and a fusible element (43) directly electrically connects the first electrode (41) and the additional electrical contact (44). An electronegative halogenated medium fills free space within the chamber. The normal current path between the first and second terminals and through the fuse is by way of the first electrode (41), the fusible element (43) and the additional electrical contact (44). The arrangement is such that when the fusible element (43) breaks, the resulting fault current forms an arc between the first electrode (41) and the additional contact (44), one root of the arc subsequently commutates from the additional contact (44) to the second electrode (35 ), the fault current flows through the coil (pb 10) and induces a magnetic field, the magnetic field causes the arc to rotate around the first electrode in the electronegative medium, and the arc is thereby extinguished, so interrupting the fault current.

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Leeds, United Kingdom

Martin C Oakes