Research status and prospect of gas-insulated metal enclosed transmission line

Gas insulated metal enclosed transmission line (GIL) is widely applied in high-power, long-distance transmission system thanks to its larger capacitance, lower transmission losses, and greater safety and environmental friendliness in comparison with traditional overhead transmission lines and cables. We reviewed GIL development's history, introduced its features, typical application situations and development status in and outside China, summarized key GIL technologies, and analyzed its development prospect from both manufacture and application perspectives. It is revealed that, with four decades of development, AC GILs have achieved comparatively mature manufacturing techniques, better structure design, more diversified installment, and greater reliability in real operation, whereas DC GILs have lagged relatively behind due to inadequate knowledge on the effect of surface charge accumulation on insulation performance as well as higher manufacturing costs. With the overall development of power industry and advancement of science and technology, future GIL studies are expected to make influencing breakthroughs in key technologies covering insulation surface charge, insulation optimization, alternative gas, as well as low-cost manufacturing. Wider application of GIL apparatus should provide necessary technical backstopping in safeguarding the operation of a clean, safe, self-recovery, economic and interactive smart grid in China.