The invention relates to an electric device (1, 20, 30) comprising a cross-linked layer (3, 4, 5, 21, 22, 23, 31, 32) obtained from a polymer composition including at least one polymer comprising at least one epoxy function, characterised in that the polymer composition also comprises a non-polymer compound as a cross-linking agent including at least one reactive function that can react with the epoxy function of the polymer in order to allow the polymer to be cross-linked.