Page 18: of Offshore Engineer Magazine (Aug/Sep 2016)

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SUBSEA FACTORY

Power

Subsea power remains on the agenda for the subsea processing containers to be used on the sea? oor.

While the project it was meant for was put on hold in 2014, systems of the future. Elaine

GE Oil & Gas went through completion of the system, which trip

Maslin surveys the main players’ successfully completed a 4000-hour testing regime late last year. This resulted in it being “the world’s ? rst system test progress in producing subsea incorporating a subsea switchgear and subsea drives.”

Gilles Chene, senior sales manager, GE Power Conversion, power distribution systems. power to magnetic bearings, instrumentation, etc. outlined the project at the Underwater Technology Conference

While subsea pumping, boosting and now compression in Bergen in June. “For us, the project started in 2007. From (with a record 43km-long 18MVA, 120Hz step out at Åsgard), 2009, testing started, followed by integration and, in 2011, have been achieved, the rollout has been limited, in terms of submerged installation at Nyhamna pit [at Shell’s plant],” he the number of projects. To date, they have also relied on being said. Testing has been running from 2012 to late last year, he he future of subsea processing systems based on connected to a topside’s variable speed drives and switchgear. said, amounting to some 4000 hours, including a 72-hour full long-distance step-outs has long been seen as a So far, only transformers and motors have been placed on the load test.

T challenge. sea? oor. The system incorporated a 20MVA transformer, switch gear

For projects requiring power for pumps, booster stations “Oil companies see the potential for subsea boosting and unit, with 35kV circuit breakers and control systems, variable or even compressors, etc., power has to be supplied from pumping, but they see the electric power system as one of speed drive (VSD), a 12.5MW, vertically installed compressor somewhere at a cost that doesn’t inhibit the economics of the the main costs, due to the cable costs,” says Asmund Maland, and 500kW pump, and other auxiliary systems. The full load project. alliance manager, ABB, on the ABB/Aker Solutions alliance, test ran with 10,100 rpm motor speed.

Subsea power distribution, through a system able to deliver formed earlier this year. “If you can make a smarter solution, “The objective was to ensure a high speed drive could be power to multiple users – pumps, compressors etc. – via one more projects will be realized.” created subsea,” Chene says. “It exceeded expectations. The power cable to the subsea system, instead of needing separate “Building platforms and shipping people back and forth is whole uninterruptable power system (UPS) proved reliable cables to each user, has been seen as an enabling technology. very expensive,” adds Jan Bugge, vice president and project through the full campaign.”

It could help to increase step-out distances and reduce costs manager of ABB and Statoil’s subsea power joint industry An “ultimate test” saw the system’s fans switched off to test for medium-long distance tiebacks, as well as reduce topside project (JIP). “By putting equipment on the seabed you can use performance and this worked, Chene says. While the system space requirements. less power, because you are closer to the reservoir, and reduce was designed to operate without fans, using natural air circu-

The challenge has been to make subsea power electronics, operational costs. That’s why this is important.” lation, it was seen that use of fans could prolong operational controls, drives, etc., work in the subsea environment, up to life.

Quali? ed 3000m deep. This includes switchgear, variable speed drives A concern around subsea power supply from encased units and controls, and auxiliary equipment. Switchgear systems GE Oil & Gas has a quali? ed system, after years of work on has been the potentially limited information available as enable many loads on one cable, for power distribution. The component, sub-assembly and full system testing for Shell’s all elements are out of reach, Chene says. To mitigate this, a variable speed drives enable the pumps and compressors to Ormen Lange subsea compression project. The system would condition monitoring system was put on all units to provide vary their speeds—this is the biggest and most complex com- transmit power from shore some 120km to Ormen Lange. GE measurements and run different data. ponent—and the controls enable remote control and moni- says the system is based on known and understood surface As quali? ed, the system could provide power to a hub, toring. The auxiliary equipment covers components such as components, which have been marinized in one-atmosphere from which power could be distributed up to 20km out to 10

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