To provide a novel composition for electrical insulation capable of effectively alleviating the electric field of a defective portion containing voids and foreign matter in an insulating layer of an insulated cross-linked polyethylene electric wire for voltage and a high voltage power cable, thereby remarkably improving water-proof tree, especially bowtightly as well as an electric wire and cable using the same.

The composition for electrical insulation contains 0.05 to 5 parts by weight of copolymer of styrene, maleic anhydride, and allyl ether against 100 parts by weight of polyethylene or ethylene copolymer or a mixture of these. The electric wire and cable are coated with the insulating layer directly on a conductor or through a semi-conductive layer.