Verification of various gas-tightness test methods for zero emission transmission products with clean air gas insulation

The paper presents investigation results of various gas tightness test methods of clean air as gas insulation in high-voltage switchgear products corresponding required tightness parameter. In particular, the following aspects compared to $\mathbf{S F}_{6}$ insulated equipment are presented and discussed in detail:(1)Quality aspects of clean air products in respect of tightness(2)Comparison between different methods of gas tightness testing to ensure the tightness of the switchgear products(3)Results of laboratory and on-site verification tests(4)Clean air aspects, practical experiences, and outlook