Abstract: In an electrolytic tank wherein cathode sheets and anode plates are arranged alternately close to each other and wherein the cathode sheets are attached to cathode bars being in contact with current rails of the tank, there is provided a method and a device for detecting and eliminating short-circuits between cathodes and anodes, in which method and apparatus the total current of each cathode bar is determined by measuring a current dependent quantity, such as the magnetic field, the temperature or similar, thereof, a short-circuit condition is recognized if the determined current exceeds a predetermined value, and, whenever such short-circuit is thus detected, the cathode sheet in question is replaced with a fresh cathode sheet by a device which is movable along rails or similar above the cathode/anode row and which is provided with a fork member or similar for lifting the defect sheet and for lowering the new sheet to replace the one removed.