Increasing deployment of floating production systems has led to a rise in the performance demands on these power cables. Darren Patel reports.
In recent years, there has been a significant rise in the number of floating production facilities used for offshore production of oil and natural gas. This trend is set to continue, particularly as energy companies move to exploit hydrocarbon reserves in deeper waters worldwide.
The design, installation and operation of high power static cables are well understood mature technology areas.
However, one of the missing elements in the power transmission system is the portion of cable that links the floating production facility with the static cable on the seabed, the electrical equivalent of a pipeline riser.
Increasing deployment of floating production systems has led to a rise in the performance demands on these power cables.
The cables must now have the ability to support increased loads caused by deeper waters and the movement of the floating vessel or platform.
They must also be able to tolerate fatigue associated with load changes that occur during their movement in the water column.
BPP-Cables, a company with an extensive background in engineering cables and umbilicals for the offshore oil and gas industry, has developed a new range of medium and high voltage cables for dynamic subsea use. One example is BPP's 132kV 100MW AC power cable design.
The first step towards meeting the design specification of this cable began with a review of potential failure mechanisms.[Page Break]
The risks can be broadly split into two groups; (i) those caused by the application of forces or conditions beyond the designs limits and (ii) longer term risks such as fatigue and corrosion.
The design and development programme allowed key attributes such as light weight, extended fatigue life and relatively low fabrication costs to be realised. Key amongst these is the selection of specialised engineering materials for key components, providing improved physical, electrical and mechanical properties in conjunction with tangible economic benefits.
The cable cross-section has been optimised in terms of component geometry, to obtain a robust, torsionally balanced, long-life cable design.
As part of the optimisation process, components were sized based on their electrical, thermal and mechanical requirements, in accordance with international HV cable standards.
Benefits of BPP's cable development work are expected to quickly accrue, both on a short-term economic level and from a longer term strategic technology perspective.[Page Break]
These benefits include the removal of power generation equipment from offshore platforms, interconnection of offshore installations, the utilisation of stranded gas for power generation and its transmission by subsea power networks to the customer.
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Darren Patel is a director with BPP-Cables, London, UK. www.bpp-cables.com
