An electrolysis system includes an electrolyzer and a conversion device for power supply of the electrolyzer out of a grid is disclosed. The electrolyzer includes a plurality of electrolysis cells connected in series to each other. The series connection of electrolysis cells is connected through a positive DC-line and through a negative DC-line to a DC-output of the conversion device. A conscious grounding of the series connection is provided via a grounding line at a connection point of the positive DC-line, at a connection point of the negative DC-line or at a connection point of an intermediate power line between two adjacent electrolysis cells. The electrolysis system has at least one overcurrent protection circuit that is arranged between two adjacent electrolysis cells of the series connection of electrolysis cells and connected in series with an intermediate power line connecting the two adjacent electrolysis cells of the series connection of electrolysis cells, and/or arranged in series with the grounding line between the connection point and ground (PE). If a ground fault is occurring at the series connection of electrolysis cells, one or more of the at least one overcurrent protection circuit is configured to trip and prevents an application of a damaging overcurrent and/or a damaging overvoltage to the electrolysis cells.