Changes in breakdown and charge migration of cellulose/oil composite after CO2 adsorption

Greenhouse gas CO2 has rarely been used as an insulating gas in cellulose/oil insulated energy devices since the benefits of it on dielectric properties of cellulose/oil have yet to be known. This work reveals that CO2 can be adsorbed by unaged and aged cellulose, improving the breakdown strength of cellulose/oil composite. The traps introduced by CO2 adsorption are proved to be the key factor. The adsorption of CO2 makes shallow traps shallower, while making deep traps deeper. These changes in traps hinder the charge accumulation on dielectric surfaces and enhance the electron capture ability in the dielectric bulk. Moreover, the charge mobility and electrical conductivity of cellulose/oil composite increase after adsorbing CO2, while the surface potential is reduced. Therefore, the collisional ionization is hindered and further electrical breakdown is improved. In the meantime, the energy level distribution models of cellulose-air and cellulose-CO2 composites were comparably studied. This work is conducive to understanding the changes in electrical properties after CO2 adsorption and the prospects of CO2 in cellulose/oil insulation.