SEACON – Subsea Power: Subsea Connectors – UT3 Magazine, August/September 2013
The Marine Renewable Energy market has emerged over the last few years as a very important new area for the use of subsea connectors.However, this sector brings with it a number of new challenges to the long-term performance of connectors, penetrators and terminations.
“As with other markets we have two basic types of connector, wet and dry-mate,” said David Pye, Renewable Energy Business Development Manager at SEACON. “Dry-mates are plugged together on the surface and then submerged whereas wet-mates are mated fully submerged.”
“In the Marine Renewables sector, both will eventually be used in significant numbers – dry-mates mainly for instrumentation on the generator and wet-mates for the connection of the main power umbilical. The use of wet-mates allow the removal of the generator from its base structure or mooring without having to retrieve this to the surface.”
“Presently, the power connectors are rated at up to 6.6kV and 1MW but there are indications that these ratings may both increase to 11kV and decrease to 3.3kV.
“All systems to date have included optical fibres for instrumentation connections – these having many advantages over copper including increased reliability and immunity to electromagnetic interference (EMI).
“There are a number of new challenges for these products which do not occur in to the same extent in other areas such as deepwater oil and gas.
The shallow water in which these generators are deployed is highly oxygenated and to some extent warmer than deep locations – this promotes the formation of marine growth and also accelerates corrosion.
“In addition, this shallow water will cause cyclic pressure changes due to wave action and the change of the tides – again not something that is of significance in deep water.
“Finally, the power connectors will see differing levels of current and voltage as wave action changes and the tides reverse. Both the design of the connector and the materials used in its construction will have to be considered with these factors in mind.
Connectors designed for these applications have to take into consideration these factors but at the same time be no more expensive (or hopefully cheaper) than existing products.
The connector industry has thus to develop almost entirely new products for the Marine Renewables sector without at present any early prospect of quantity production – quite a challenge,” said Pye.