2005-10-03 - Troll A in the North Sea is the first offshore platform in the world to be powered by direct current (DC) electricity originating on land – an achievement made possible by ABB technologies that bring considerable savings, lower costs and environmental benefits.
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Located about 70 kilometers off the coast of Norway and operated by Norwegian oil giant, Statoil, the Troll A gas platform has been in use since 1996 and now satisfies 10 percent of Europe's total natural gas demands.
In order to maintain the platform's gas-delivery pressure and compensate for falling reservoir pressure, two 40-megawatt compressors were brought online on October 1, 2005.
Ordinarily, a conventional power generation system using gas turbines or diesel engines would create the electricity needed to run the platform compressors. But conventional systems can be less efficient even under ideal conditions, and create greenhouse gas emissions.
ABB has deployed two key technologies - HVDC Light (High Voltage Direct Current) and the VHV Motor (Very High Voltage) - as well as other solutions to bring clean power from the Norwegian mainland 70 kilometers away to power the compressors.
Major savings
Core component of ABB's HVDC Light system are valves which consist of millions of high power semiconductors. The valves are shielded and suspended from the ceiling in an extremely compact converter module. The semiconductor design allows less than one failure per 10 million operating hours. HVDC Light is a unique and proven power transmission system, specially designed to transmit power underground and underwater.
That adds up to major savings, lower costs and the elimination of greenhouse gas emissions from the platform.
The benefits of transmitting power from shore to platform – already apparent in the trial phase – include zero pollution (all electricity used on Troll A is generated by hydropower on the mainland), increased transmission efficiency, longer equipment lifecycles, fewer maintenance stops, fewer offshore workers, and a perfect health and safety record on the platform.
“It is a tremendous technological achievement, and one that may well be copied at other platforms in the future as the cost and environmental savings become more widely known,” said Samir Brikho, head of ABB’s Power Technologies Systems business.
“This project also underlines ABB’s continuing commitment to the oil and gas industry, and highlights our ability to deliver state-of-the-art technologies that increase productivity and power reliability, while lowering environmental impact.”
Transmitting power from shore to platform eliminates annual emissions of some 230,000 tons of CO2 and 230 tons of NOx , including the onshore gas treatment plant at Kollsnes.
Avoiding tax on CO2 emissions also cuts costs, while carbon trading supported by the Kyoto protocol creates added value (CO2 currently trades at more than 20 Euros per ton on the European Energy Exchange).
State-of-the-art
In ABB's Very High Voltage Motor, cables insulated with cross-linked polyethylene (XLPE) replace the square, epoxy-insulated conductors used in conventional electric motors. The cooling ducts shown in this cross-section are also made of XLPE. Most of the materials in the VHV Motor can be easily recycled.
Troll A’s power needs are met via ABB's cable-wound, VHV Motor and generator on the platform; power is transmitted from shore through HVDC Light cables on the seabed.
ABB's key technologies on Troll A are:
- Two 40-megawatt high-voltage ABB VHV Motors that drive the compressor units, with associated utilities. The VHV Motor can be used in any application where conventional synchronous machines are used, both onshore and offshore. It can be linked with high-voltage input, without a step-down transformer.
- HVDC Light, a power system designed for underwater and underground transmission. HVDC is used mainly for bulk power transmission and for the interconnection of independent power grids. HVDC lines cannot be overloaded, ensuring reliable power.
The new compressors will increase production to 100 million cubic meters of gas per day, from 85 million cubic meters. Troll A produced 26.39 billion standard cubic meters of gas in 2004.
Significantly, the technologies – and avoiding onboard power generation – mean no injuries and no loss of time through incidents, a key element in Statoil’s business strategy.
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The Troll A gas platform is the first offshore platform in the world to be powered by a direct current (DC) electricity link originating on land. On the platform ABB has deployed two key technologies - HVDC Light and a Very High Voltage Motor - as well as other solutions to help power the two 40-megawatt compressor units on the Troll A platform without any local power generation. This adds up to major emission savings and lower costs.