Insulation defects at the side of the conductor screen layer of service-aged cross-linked polyethylene（XLPE）cables have not attracted sufficient attention. In this paper

the very-low-frequency dielectric loss tests and microscopic physical and chemical properties analysis were respectively performed on new cables and service-aged cables. It is proved that the retired cables were seriously aged and continuous sheet ageing insulation defects could be found at the side of conductor screen layer. According to the scanning electron microscope（SEM） observation

some of micro voids exist in conductor screen layers and insulation layers of aged cables. Based on the analysis of energy dispersive spectrum

there is a small amount of aluminum in the conductor screen layer and the inner insulation. Besides

degradation of ethylene-vinyl acetate（EVA） copolymer in the conductor screen layer is verified according to infrared spectroscopy（IR） test results

and new absorption peaks of hydroxyl and carbonyl groups can be found in the infrared absorption spectrum. Therefore

degradation of EVA in conductor screen layer of service aged cables can take place during the operation process

and degradative products can get into the inner insulation

which can further participate in the oxidative degradation reaction of XLPE and further lead to the formation of continuous sheet aging insulation defects on the side of conductor screen layer.