Electric power supply to oil and gas platforms is conventionally provided by gas turbines located on the platforms. As these gas turbines emit considerable amounts of CO2 and NOx, it is desirable to find alternative solutions. One alternative is to feed the platforms from the onshore power system via subsea power cables, which already have been implemented on some platforms in the Norwegian part of the North Sea. The paper studies a cluster of petroleum installations in this geographic area, connected to the Norwegian onshore power system through an HVDC voltage link. In the study, an offshore wind farm is also connected to the offshore AC power system. The main focus is investigation of transient stability in the offshore power system, and several fault cases have been studied for different levels of wind power generation. Simulations show that faults on the offshore converter platform can be critical due to the dependency of the reactive power delivered by the HVDC link to the offshore AC system. However, it is shown that local wind power production matching the offshore power demand will improve both voltage- and frequency-stability. Further on, it is indicated that offshore reactive power injections or alternative wind farm control topologies could improve voltage stability offshore. (C) 2012 Elsevier Ltd. All rights reserved.