1600 MVA ELECTRICAL POWER TRANSMISSION WITH AN EHV XLPE CABLE SYSTEM IN THE UNDERGROUND OF LONDON

摘要

For 1600 MVA bulk power transmission in the underground of London a 400 kV XLPE cable system was planned and developed to fulfil the increased power consumption of the mega polis.This project sets a new milestones for the European XLPE cable technology for project engineering, cable system dimensions and transmission rate and testing:A 20 km long tunnel with an inner diameter of 3 m was driven through the London underground in a depth of approximately 30 m which allows a straight route independent from the surface situation.The tunnel will show a cooling system with forced air to increase the transmission capacity of the cables which are installed in a vertical flat formation. Temperature monitoring along the tunnel route and cable screen will optimise the load situation of the cable to ensure a continuous transmission capacity of 1600 MVA for one cable system.The delivered cable lengths up to 1000 m leads to a total drum weight of 471 which has to be handled during production, shipping, and installation. This extreme long cable length was chosen to reduce the total number of joints. The complete cable system consists of 60 km cable, 60 cross bonding joints, and 6 GIS terminations.The EHV XLPE cable shows an insulation thickness of 27 mm. The cable outer sheath shows an extruded flame retardant layer to prevent the development of fire along the tunnel.In order to qualify the full cable system a type test and a pre-qualification test according IEC 62067 has been successfully carried out at independent testing institutes.The on-site AC testing procedure will set a new mark: At an AC voltage of 280 kV 20 km of 400 kV cable and 20 joints will be simultaneously tested and PD watched.