Pressurized Air Cables - a new technology for sustainable energy transmission 12 kV - 420 kV

Abstract:
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 flange design without bolts allows fast assembly and disassembly, compact dimensions, and a maximum operating air pressure up to 10 bar. With the proposed design, SF6-free pressurized air cables have similar flange diameter than existing GIL using SF6 or other insulation gas mixtures. Pressurized air requires larger insulation gaps and therefore PAC have larger aluminium conductor cross sections >2200 mm(exp2). These large cross sections improve efficiency and reduce losses and all heat related issues during engineering and operation. The PAC component portfolio includes straight bus, 90 deg angle pieces, compensators and bushings. Bursting pressure tests results confirmed mechanical integrity up to 50 bar. High-voltage and high current testing according to IEC 62271-204 confirmed specifications for each, a 52 kV, 2000 A and a 145 kV, 2500 A product. The enclosure temperatures remain below 65 °C for rated current applied for > 10 h and outside magnetic field is <1 muT in >1 m distance. Short-circuit current testing confirmed performance up to 59 kA, 1300 ms; 130 kApeak and internal arc fault tests showed enclosure integrity up to 55 kA, 1500 ms without using rupture discs. Installation examples into confined spaces such as pipes and microtunnels using a proprietary roller system are provided. It is concluded that pressurized air insulated cables are a viable, type tested, SF6-free solution for medium- and highvoltage electric energy transmission – which can replace high-voltage lines and HV cables with reduced environmental impact and improved technical characteristics.