In 2014, the national transmission system operator in Norway, Statnett, commissioned a new 13-km (8-mile) 420-kV submarine cable interconnection across the Oslo Fjord to replace a time-expired 12-km (7.5-mile) 420-kV interconnection comprising six 420-kV single-core fluid-filled (SCFF) cables in service since 1981. This interconnection is part of an important circuit in the Norwegian grid, with the demand for more transmission capacity was one of the reasons for installing the new cables.
The project consisted of:
Pre-removal survey
Oil draining from cable ends
Mobilization for marine operations
Removal of concrete culvert covers
Removal of cable joint protection mattresses and joints
Cutting and sealing of cables outside the four landfalls
Cable retrieval
Cable disposal
Removal of the oil-pressure system and termination buildings, in parallel with the maritime scope
Einar Tommelstad is a project engineer at Statnett SF. He holds a master’s degree in energy and environmental engineering from the Norwegian University of Science and Technology. Tommelstad has worked for six years at Statnett on many different high-voltage cable projects.
Carl Erik Hillesund
Carl Erik Hillesund is head of the cable department in the technology and development division at Statnett SF. He holds a master’s degree in electric power engineering from the Norwegian University of Science and Technology. Hillesund worked as a consultant for more than 15 years before joining Statnett eight years ago.