The DC variant of the GIL would make power transmission routes more environmentally compatible and cheaper
April 9, 2015
Siemens develops a gas-insulated transmission line for carrying large amounts of energy at high DC voltages. Berlin Technical University and Dresden University of Applied Sciences, among others, are working under the lead management of Siemens on developing a new gas-insulated DC transmission line, known as the DC CTL (Compact Transmission Line for Direct-current High Voltage) for laying underground. The new line is designed to transmit up to five gigawatts (GW) of power per system. The German Federal Ministry for Economic Affairs and Energy (BMWi) is providing EUR 3.78 million in this development project.
The DC CTL will be based on the technology of the existing gas-insulated transmission line (GIL), which consists of two concentric aluminum tubes. A mixture of gases is used as the insulating medium. Until now, the GIL has only been available for alternating current (AC). The challenge for the DC CTL is posed by the special design of the components taking into account their specific properties at high direct voltages. Because of its significantly higher current-carrying capacity of up to 5000 amperes (A), the DC variant of the GIL would not only be able to transmit the required amounts of electrical power more efficiently compared with cable in the future grid upgrade, it would also make power transmission routes more environmentally compatible and cheaper.
Developing the grid using high-voltage direct-current (HVDC) transmission technology with overhead power lines and gas-insulated DC transmission lines buried underground over certain sections could be implemented using considerably less resources than three-phase technology.
Gas-insulated DC lines can handle the power from an overhead line with the same number of conductors. This means that the substations and transmission corridors can be designed to take up less space, which makes them more cost-efficient.
