The process for making extra high voltage cable insulation is improved by using a composition comprising in weight percent based on the weight of the composition: (A) 95 to 99.9% of an ethylene-based polymer; (B) 0.2 to 2.5% peroxide; (C) 0.01 NI to 0.5% of a sulfur-containing first antioxidant having at least one —S(CH2)2CO2R group, wherein R is a C6 to C20 alkyl; (D) 0.001 to 0.009%) of a phosphorus-containing second antioxidant that does not contain a —S(CH2)2C02R group, wherein R is a C6 to C20 alkyl; (E) Optionally, an organic nitrogenous base; and (F) Optionally, a phenolic third antioxidant that does not contain a —S(CH2)2C02R group, wherein R is a C6 to C20 alkyl.