Submarine Power Cable

Submarine power cables have been around for more than a century and the major use has shifted through the decades. In the early times, Submarine power cables were used to supply isolated offshore facilities such as lighthouses, infirmary ships, etc. Later, the power supply of near-shore islands was the main objective of subma­rine power cables. The connection of autonomous power grids for the sake of better stability and resource utilization has been pursued since the sixties of the last cen­tury. In modern days, the connection of offshore facilities is again in the focus. Oil and gas production units ask for shore-generated power, while offshore wind parks (OWP) need to bring their precious green power to the onshore grids.

Power Supply to Islands:

Islands located closely to the mainland can be connected to the mainland grid by submarine power cables. This is normally done with medium-voltage AC cables (<52 kV) and a transmission power of 10-30 MW per cable. The Submarine power cables replace island-stationed, often-inefficient power generation such as diesel generators. The maximum economic length of these cables is 10-30 km. In response to increased power demand of the island, additional cables are often laid in different routes to reduce risks and increase the power availability on the island. The island supply can be secured by other cables even in the case of a cable failure. The archipelago of the North Frisian Islands in Northern Germany was connected the mainland by a grid of 20 k V submarine cables starting in 1944. Other islands like Vancouver Island, Canada, and Long Island, NY, USA, have a large population and massive power demands requiring a number of extra high voltage Submarine power cables circuits.

The supply of distant islands is difficult as losses in AC cables increase dramat­ically with distance. Islands located more than 50 km from the mainland have not been connected for a long time. The German tourist island of Heligoland will be connected to the mainland only later this year (2009). The Swedish island of Gotland is some 100 km off the Swedish mainland and had to rely on inefficient diesel power generation for a long time. The island wasn't connected to the mainland grid until 1954, when the first submarine HVDC cable was installed. The canal islands of Jer­sey and Guernsey were connected to the French mainland in 1987 and again 2000, and the Italian islands of Sicily and Sardinia were connected to the Italian mainland by submarine power cables.

Questionnaire:

• Explain about submarine power cables.