Securing a line

A device is proposed having at least one sensor (105, 106; 203; 301, 302; 504, 505; 601; 703; 801, 802), by means of which an electrical variable at at least two locations of a line (101; 201, 202 ; 305, 306; 501; 702) is determinable, and with an evaluation (109; 205; 304; 805) by which the electric quantities are evaluated, wherein the evaluation is adapted depending on an evaluation result a separator (104) so to control that it interrupts a current flow in the line. Furthermore, a corresponding method is specified.