A method for preventing an electrical grid from failure in case of a temporary overvoltage includes providing an electrical grid line, a surge arrester and a disconnector device with a disconnector unit. The method further includes connecting the surge arrester at one terminal to the electrical grid line, connecting the surge arrester at its other terminal to a first terminal of the disconnector device, and connecting a second terminal of the disconnector device to ground potential. The method further includes interrupting the electrical connection in between the electrical grid line and the ground potential in response to a temporary overvoltage. The method further includes protecting the surge arrester from failure due to a thermal overload caused by the temporary overvoltage by operating the disconnector device before the surge arrester fails due to a thermal overload of the surge arrester.