Offshore Substation Platform Expandability Index
With the increasing number of offshore wind farms being planned in North America in the next decade, many jurisdictions including New York State Energy Research & Development (NYSERDA) are looking into possibilities of requiring future expandability of offshore substations to enable future connection of radial export transmission links into an interconnected offshore grid.
Offshore grid expansions can realize redundant capacity, redundant auxiliary power and they can enable offshore substations to act as ‘stepping-stones’ for more remote offshore substations. They can also be used to service different purposes such as connecting offshore loads to wind farm collector systems, or to create transmission capacity between two onshore points of interconnection in addition to exporting offshore wind power. Depending on the type of offshore grid expansion, different technologies such as medium voltage AC, high voltage AC or even HVDC can be used.
The different types and technologies of offshore grid expansions require different levels of preparation for offshore substations that have to be made in order to enable this expandability. Some must be made at the time of designing, manufacturing the equipment at the factory and building the platforms at the yard, others can be made at a later stage during onsite installations. The platform readiness to accept additional cable connection(s) also determines the required upfront (anticipatory) capital investment. Depending on the certainty of the future expansion, different levels of preparedness, and thus different levels of associated anticipatory investment, can be chosen in order to manage the risk of stranded assets. In this paper, different types of offshore network expansions are first summarized, followed by different modifications this would require to existing offshore infrastructure, and the different levels of associated preparedness for future/planned substations. The modifications are discussed by considering the impact on system design, primary equipment, secondary equipment, SCADA and structural aspects. Conceptual details are provided and accompanied by real world experiences from recent European projects.
Offshore Electrical Lead, Principal Engineering, DNV
Principal Consultant, DNV
Floating Offshore Wind Expert, DNV