Engineering and interfaces of Pressurized Air Cables for MV and HV projects

Pressurized Air Cables (PAC) are essentially gas-insulated lines which use pressurized air for insulation between a HV conductor and its coaxial enclosure tube. A newly developed boltless flange design allows fast assembly and disassembly, compact dimensions, and operating air pressure up to 11 barabs. The PAC component portfolio includes straight connections, angle pieces, flexible pieces, and bushings to fit most cable project requirements. PAC can replace overhead lines and XLPE cables with higher continuous current ratings up to 4000 A, reduced ohmic losses, lower reactive power, and fireproof, internal arc resistant enclosures. As a new technology used for customer specific engineering projects, it is essential to gain engineering experience on different project setups and interfaces to confirm usefulness and versatility of the PAC engineering tools and its components portfolio. Due to their different base design and main insulation gas, PAC require substantially different interfaces and on-site installation procedures. A variety of interfaces such as air bushings, cable termination, transformer direct connection, GIS direct connection, and adaptation to existing GIS are detailed in this paper. Alle interfaces required a complete development for high-voltage design and testing using pressurized air as insulation medium. These interfaces cover most of the requirements for pressurized air cable connections in a substation and as a replacement of overhead lines. Engineering examples are provided for a 36 kV test installation in a concrete trench and a 145 kV cable connection on a substation with direct connection to an SF6 free GIS on one end and a direct transformer connection on the other end. These examples are typical applications which have been successfully installed, energized, and operated. It is concluded that all typical interfaces for MV and HV cabling projects can be provided for pressurized air cables. Project engineering was successful for differing project requirements which indicates that a large variety of engineering options can be facilitated. PAC are therefore a new cable technology which supports the transition to a more efficient, sustainable, robust, and environmentally friendly electric grid.