Design and implementation of compact and robust medium voltage switchgear for deepwater work-class ROV ROSUB 6000

摘要

The present paper presents the design and implementation of compact and robust medium-voltage switchgear for the deepwater remotely operated vehicle (ROV) ROSUB 6000. Electrical and control systems in the tether management system (TMS) and the ROV are powered by a voltage of 6.6kV at 460Hz transmitted through 6,000m umbilical and 400m tether cables. Any fault in an ROV system could lead to failure of the complete system. Thus the ROV needs to be isolated by medium voltage switchgear located in the TMS. Using conventional circuit breakers inside pressure-rated enclosures with feed-through could be a possible solution, but they are not attractive because they affect the volume occupied and thus weight and costs. The proposed solution involves adoption of a low-voltage air break contactor in an insulating oil-filled pressure-compensated enclosure and uses the subsea environmental conditions to operational advantage. To further ruggedise the oil-filled pressure-compensated switchgear and make its life-time independent of load break conditions, the switchgear opening sequences are controlled using programmable automation controllers distributed in the ship, the ROV and the TMS. The hardware developed is proven to work according to the requirements. The present paper further explains the extendibility of this idea to futuristic subsea systems that will involve high-power switching operations.