The line differential protection SIPROTEC 7SD80 has been conceived for selective line protection of power cables and overhead lines up to 24km for all kind of starpoint configurations. The implemented phase comparison algorithm is a fast and stable method for line protection in industry and distribution grids. The protection interface communication is carried out directly without external equipment over copper wires, optical fibers or both in redundancy. The wide scope of non directional and directional functions can be applied miscellaneously as emergency functions as well as backup functions. For instance, the SIPROTEC 7SD80 enables simplified and cost saving concepts for meshed grids and busbar protection by means of reverse interlocking.