Analysis of AC 500kV XLPE Submarine Cable Insulation Laboratory Aging Condition Based on Frequency Domain Dielectric Spectroscopy

With the rapid rise of new energy industry and its rapid development all over the world, there is a great market for submarine cable products. The world's first class AC 500kV cross-linked polyethylene (XLPE) insulated submarine cable will soon be put into operation in the “Zhoushan-Ningbo” interconnection project. Aging of insulation materials after operation will be an important factor restricting the safe operation of the 500kV XLPE cable. Taking into consideration that the frequency domain spectroscopy (FDS) is a nondestructive testing (NDT) method, in this paper, the changes of dielectric spectroscopy of the AC 500kV XLPE submarine cable material during 130°C thermal aging process were studied. The aged samples show increasing dielectric constant and dielectric loss. Besides, Iε` is defined to estimate the aging condition of XLPE samples. It can be clearly seen that the samples severely aged when the Iε' exceeds 1. The Iε' can be used to diagnostic the aging condition of the AC 500kV submarine cable insulation material. Besides, the ε`rand tanδ in the lower frequency of the seriously aged sample increase significantly, and the inflection points of tanδ curves for the seriously aged sample move to higher frequency significantly.