High-voltage cable provided with insulator made mainly of ethylenic polymer having high resistance against formation of water tree

PURPOSE: To enhance resistance against formation of a water tree by containing two kinds of a specific ethylenic polymer at specific ratios and a conventional additive in a conventional quantity. CONSTITUTION: A cable insulator has cable resistance against generation and growth of a water tree, and includes 70-99 parts by weight of an ethylenic polymer I, 80-92% by weight of ethylene, 8-20% by weight of C4 to C10 -α-olefin, 1-30 parts by weight of another ethylenic polymer II having a density of 0.890-0.915G/cm and a crystalline melting point of 90-125 deg.C and being different from the polymer I, and a conventional quantity of a conventional additive. Consequently, it is possible to provide a high-voltage cable of 1-500kV with the cable insulator including as basic compositions the ethylenic polymers and having an excellent treating performance and a high mechanical strength, and being capable of suppressing generation or growth of a water tree and exhibiting a slight inductive loss ratio and a high aging resistance.