Electrical studies for subsea interconnection of floating units

The electrical interconnection of floating units (FPSO, CPF, ..) with long subsea cables becomes more and more common. It is a solution to optimize redundancy and capacity of the electrical power supply. But this type of connection leads to specific technical issues that are not addressed in classical electrical design. Load flow and transient stability studies involve new cases where generators of one unit supply loads of the other one (interconnector tripping, distant motor starting ...). Electrical stability of interconnected power station is limited and has to be assessed. The electrical load sharing between generators becomes more complex and new features have to be included into the energy management system. Large interconnection transformers have to be energized by generators with potential risks of resonances. This shall be analyzed with electromagnetic transient simulations. This paper will discuss electrical issues to be addressed and will show some typical cases where problems can be foreseen thanks to simulations studies. From this experience, some general recommendations are proposed for the electrical design.