Abstract: A submarine branching unit is disclosed that includes a termination for each of at least three line cables and a termination to sea ground. A relay is positioned between each pair of cable terminations. When current flows between two of the cables, the intermediary relay will become energized and cause a contact to connect the third cable to the sea-ground termination. To avoid dangerous surges in current to sea ground when a relay trips, a current limiter is placed in series with the sea ground termination.

Abstract: A submarine branching unit including at least one power relay having two separate coils, rather than a single coil. The first coil provides an initial magnetic field capable of closing an electrical circuit contact, while the second coil provides a redundant magnetic field that reinforces and backs-up the magnetic field generated by the first coil. The first low-voltage isolated coil of the relay is positioned in the path of the main trunk in a submarine communication system, and the second high-voltage isolated coil is located in the spur branch connected to sea earth. By this double-coil configuration, the independent and redundant relay power system ensures that the charged spur cable is not switched back to the main trunk when an open circuit occurs or any equivalent system failure that could show a current dropping to zero while the system voltage remains non-zero, avoiding high current passing through relay contacts and subsequent dangerous arcing, each being a possible cause of relay failure.

Abstract: A submarine branching unit is disclosed that includes a termination for each of at least three line cables and a termination to sea ground. A relay is positioned between each pair of cable terminations. When current flows between two of the cables, the intermediary relay will become energized and cause a contact to connect the third cable to the sea-ground termination. To avoid dangerous surges in current to sea ground when a relay trips, a current limiter is placed in series with the sea ground termination.

Abstract: A submarine branching unit including at least one power relay having two separate coils, rather than a single coil. The first coil provides an initial magnetic field capable of closing an electrical circuit contact, while the second coil provides a redundant magnetic field that reinforces and backs-up the magnetic field generated by the first coil. The first low-voltage isolated coil of the relay is positioned in the path of the main trunk in a submarine communication system, and the second high-voltage isolated coil is located in the spur branch connected to sea earth. By this double-coil configuration, the independent and redundant relay power system ensures that the charged spur cable is not switched back to the main trunk when an open circuit occurs or any equivalent system failure that could show a current dropping to zero while the system voltage remains non-zero, avoiding high current passing through relay contacts and subsequent dangerous arcing, each being a possible cause of relay failure.