Lastbrytare

Lastbrytare is a switching device used in electrical power systems to interrupt current to a load while the circuit is energized. It is designed to isolate a part of the network for maintenance or fault management and is typically found in medium-voltage switchgear and distribution boards. A lastbrytare can break load current, but many installations pair it with protective devices such as fuses, meaning the device itself does not have to withstand the full fault current.

Construction and operation commonly involve multiple poles with stationary and movable contacts, housed in a protective enclosure. The device includes an arc-arresting or arc-quenching mechanism to limit arcing during opening, enabling switching under load. Lastbrytare can be operated manually by a handle, or motorized and integrated into remote or automated control systems. In practice, a lastbrytare is often part of a fuse-switch combination, providing both disconnection and protection, or it may work alongside separate circuit protection.

Applications and use cases include sectionalizing a distribution feeder, isolating circuits for maintenance, and enabling controlled load shedding in substations. They are selected according to voltage rating, current rating, and breaking capacity, with consideration given to the expected fault currents and duty cycles of the network.

Safety and standards: Operation requires trained personnel, proper lockout/tagout procedures, and adherence to national electrical safety regulations. Design, testing, and installation of lastbrytare are governed by relevant standards and certifications from international and regional bodies, such as IEC-based specifications, to ensure reliable performance and safe operation in electrical networks.