High Voltage Electrical Connectors

Existing designs for subsea, wet-mateable electrical connectors are based on maintaining the electrical contacts in an insulating liquid or a gel that is pressurebalanced with the subsea ambient pressure. These high voltage connector designs are being developed from the low voltage, subsea, and wet-mateable connector designs that are currently in use in subsea applications.

However, the inherent deficiency of this liquid filled, pressure-balanced design philosophy when applied to subsea high voltage equipment, is that the insulating liquid is degraded in the long-term due to the breakout of water molecules. These water molecules cause a potential risk by linking to produce tree-like formations between phases. This phenomenon has been well studied and documented for domestic high voltage equipment such as oil filled distribution transformers. In these circumstances, the usual barrier seal methods of exclusion are ineffective against water ingress, which may occur due to osmosis through the seawater/dielectric liquid seal, especially where the insulating liquid is at ambient pressure. Furthermore, the integrity of electrical connectors for subsea use could be required to be maintained over a twenty-year equipment lifespan.

Water treeing has not yet been physically proven as a limiting factor with the fluid filled, pressure-balanced, subsea, electrical connectors as none have yet been used in long-term, high voltage, subsea applications. However, it is documented that the risk for water treeing increases considerably with increasing voltage as any water already in the insulating oil tends to come out of solution. This fact makes it of value to eliminate the potential risks by avoiding the use of a dielectric liquid.

There is extensive long-term experience with high voltage electrical contacts that are maintained in gas environments at atmospheric pressure. The design philosophy of the ELEx subsea wet mateable high voltage connector is therefore to eliminate water treeing as a failure mechanism for the connector by maintaining the electrical contacts in a gas environment at a pressure of one atmosphere.