The present invention relates to a device and a method for reliably securing an electric line with a controllable switching element, wherein the device and the method can be easily adapted to the properties of an electric line. The device comprises a controllable switching element (110, 610) that is designed to take on at least two states, specifically a first state with a first resistance and a second state with a second resistance that is lower than the first resistance. The invention further comprises a current measuring device (120, 620) for measuring a current via the line; an averaging device (125, 625) for determining at least one first current pulse on the basis of the measured current, averaged over a first duration, and a second current pulse, averaged over a second duration that is longer than the first duration; and a controller (130, 630) for controlling the switching element such that the switching element switches into the first state when the first or the second averaged current pulse exceeds a first or second threshold value of a tripping characteristic curve.