A power supply system, particularly to be used in maritime oil/natural gas production includes at least one data transfer/voltage conversion unit arranged above sea level and one electrical means such as a choke, gate valve, production tree, power control/communication unit and the like arranged below sea level, which are electrically connected via a cable connection at least for power supply.To improve such a power supply system in a manner that this system has a simple structure and each data transfer/voltage conversion unit can also provide higher powers over a predetermined period of time or during continuous operation, a plurality of data transfer/voltage conversion units are arranged modularly, and one additional power supply module can be connected thereto to increase the power supply, and the electrical power, respectively.