The design of the NEPTUNE power system

The proposed NEPTUNE observatory will include about 30 locations on the Juan de Fuca plate where scientific instruments can be connected for communication and power. The NEPTUNE power system is required to make available at each location the largest amount of power possible, using conventional submarine telecommunications cable. The power delivery system is based on the use of a standard cable, but it is used in an interconnected network in order to maximize both reliability and power level. The cable will be energized with medium voltage ~10 kV DC and have parallel loads, a combination that has never been built before as an interconnected network. During normal operation, it is calculated that a power level of over 5 kW can be delivered to each of the 30 nodes. Should it be needed, as much as 40 kW can be delivered to each of 3 nodes on the far west of the network, 500 km from shore, provided the power on all the other nodes is reduced to 1 kW. These power levels and distances are considerably greater than has been achieved in previous undersea observatories. The design of the sub-sea node is based on the use of grouped switching mode power supplies with series-connected inputs and parallel connected low voltage outputs. The ocean is used as a return path. Consideration of the reliability of the system plays an important role in the design of the power system. A scheme of protective relaying will enable the delivery system to continue operation even with faults in part of the network