Advances in High-Power Connector Technology
Authors: Marklove Michael C. 
Published: October 2008

The increase in the use of electricity to power subsea processes is expected to continue through this decade. To provide the power necessary to operate a network of production equipment, a Joint Industry Project has been established to develop a transmission, distribution and control system capable of operating at depths of up to 3000m. With the capacity to deliver up to 30MVA, it is anticipated that this will meet the demand for electrical power in the foreseeable future.

Key to the success of the programme is the development of a reliable, subsea mateable connector that can operate at system voltages up to 36kV but that has been tested to 76kV. This is a new requirement for a wet mateable power connector that has not been realised previously. The programme to develop the connector commenced in September 1999 and this paper describes the progress so far.

Introduction

The last five years have shown a marked increase in the use of electricity to power subsea processes. Recent concepts have seen the development of systems using electricity to drive downhole pumps; subsea separators & injectors; multi-phase pumps and flowline heating systems, all of which are designed to improve performance and make production more economical. Such measures are becoming increasingly important as operators strive to remain competitive by reducing production costs.

As the oil and gas industry gains more experience in the use of electrical systems subsea, the application of such systems to achieve process improvements and cost savings is expected to proliferate. Even now, operators are exploring the possibility of relocating topside processing equipment to the sea floor to take advantage of proximity to the wellhead. Allied with this is the opportunity to exploit wells at long stepout distances using existing infrastructure rather than expending large amounts of capital on a network of new platforms. In this case the concept of the all-electric well is conceived, with auxiliary power being used to drive actuators and chokes on the tree.

In anticipation of this increase in demand for electricity subsea, a Joint Industry Project (JIP) was formed in 1995 to assess the feasibility of operating a control and distribution system on the seabed. The project, known as SPEED (Subsea Power Electrical Equipment Demonstrator) was led by ALSTOM and culminated in the development of a 1MW system capable of operating at depths of up to 300m1. This system used a Tronic 11kV three-phase, wet-mate connector to make the connection between the umbilical and the distribution system. However, as the potential applications for subsea power distribution emerged, it became apparent that variable speed drives would be required that were capable of operating motors with outputs up to 2.5MW. This has resulted in a considerable escalation in the total demand for subsea power to the extent that schemes have been proposed for which the total load is 30MVA. It also became apparent that the deployment depth would need to be increased. Hence, the original SPEED concept required enhancement to meet these increased requirements.