New lease on life for northern European power link

2007-12-19 - ABB has rejuvenated a 30-year old power cable link between Norway and Denmark by replacing the outdated control system, ensuring this connection will deliver reliable power for decades to come. The work was completed in record time.

By ABB Communications

After starting service life in 1976 and 1977, the power cables at the bottom of Skagerrak Strait remain in top condition today, good for an estimated two decades of additional service. But the control system was a concern for ABB’s customers, Energinet.dk of Denmark and Statnett of Norway.

"The control system had passed its estimated lifespan and there was a risk that the number of faults would increase,” said Halvard Thommessen, the project leader at Statnett.

ABB has won six orders to upgrade aging high-voltage direct current (HVDC) links, and the Norway-Denmark contract is the fourth to be completed. HVDC was developed by ABB more than 50 years ago, and allows large amounts of power to be transported over long distances while also providing more stability to electricity networks.

Mach 2
ABB won a contract to provide its Mach 2 protection and control system, which is specifically designed to work with HVDC and flexible alternating current transmission systems (FACTS).

Its distinguishing feature is an unequalled capacity for fast calculation provided by a 1.8 GHz Pentium M-processor and a number of fast digital signal processors. This compact design gives the system better control in the event of faults and disturbances.

"We had never made an upgrade that fast" says Mikael Persson, ABB project manager.
The Mach 2 units were shipped to the converter stations in Norway and Denmark in the first half of 2007, so tests and simulations could begin.

“In the contract we promised we would not interrupt the system for more than two weeks for the installation,” said ABB’s project manager Mikael Persson. “We had never made an upgrade that fast; achieving it would set a record. But every day the link is closed means lost revenues for our customers, so time was a very important factor.”

Precise timetable
ABB began by installing computer systems and drawing up a detailed work schedule at the converter stations in Kristiansand, Norway, and Tjiele, Denmark.

The Skagerrak control system before the upgrade. It had passed its estimated lifespan, increasing the risk of faults.

“We had to have a precise timetable showing what we needed to accomplish, almost hour by hour,” said Persson. “So at the end of each day, we knew exactly where were stood.”

Work finished the day before the end of two-week deadline. A three-month test period then began during which the connection had to operate 100 percent of the time, according to the contract.

“Everything went according to plan,” said Svend Erik Pedersen, an HVDC specialist at Energinet.dk, allowing Energinet and Statnett to resume responsibility for operations in November 2007.

Extending the life of HVDC systems
ABB has refurbished three HVDC links besides the one connecting Norway and Denmark, all of them in the U.S. Two more upgrades are in progress, in South Africa and the U.S.

Several other HVDC connections built at the end of the 1970s are likely to require an overhaul in the coming years. The critical factor in these upgrades is knowledge of the control systems. ABB so far is the only supplier to carry out this type of operation.

Skagerrak upgraded with ABB's Mach 2 control system, which can extend the life of high-voltage DC cable systems.

The Mach 2 control system evolved with the experience gained from ABB’s unequalled base of HVDC control systems around the world. It is used in all ABB’s FACTS installations and in applications using HVDC Light, a technology that is particularly well suited to underground transmission of high-voltage power and to connecting offshore wind farms to the grid.

The Mach 2 system allows a high degree of integration and can handle all control and protection functions as well as advanced fault registration and remote control functions. The structure, with central computers and remote I/O units that communicate over fast field buses, is flexible and suits new installations as well as upgrades of existing control systems.

The Skagerrak Strait runs between Norway and the southwest coast of Sweden and the Jutland peninsula of Denmark, connecting the North Sea and the Kattegat Strait leading to the Baltic Sea.



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    ABB is upgrading several HVDC links around the world, and many other connections build in the late 1970s are expected to require an overhaul in the coming years. ABB is so far the only supplier to carry out such work.

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