Breakdown Performance of Compound Structure of Semi-conductive Layer and Insulating Layer for Submarine Cable

Submarine power transmission project has been recognized as one of the most complicated and difficult large-scale projects. Submarine cable as an important part of the power transmission project, its breakdown performance is very important, but there are few reports about breakdown performance of submarine cable. In this work, breakdown performance of compound structure of semi-conductive layer and insulating layer for submarine cable is studied. Firstly, compound structure samples of semi-conductive layer and XLPE insulating layer used for AC submarine cable are fabricated by the hot-melt welding method, and semi-conductive specimens with different carbon black (CB) contents are fabricated for experimental comparison. The morphology, resistivity of semi-conductive shielding layer and breakdown strength of semi-conductive layer and insulating layer are measured separately. In the temperature range of 30–100 °C, the resistance of the semi conducting shield increases, reaching the maximum value of
$94.2\ \Omega \cdot \text{cm}$
at 100 °C. Moreover, the resistivity of the semi-conductive shielding layer is relatively large as a whole. The scanning image shows that there are large carbon blocks in the semi conducting shielding layer of submarine cable. At room temperature, breakdown strength of compound structure of semi-conductive layer and the insulation layer is 107 kV/mm. The maximum compound structure breakdown strength of CB/LDPE/EVA semi-conductive layer and the insulation layer is 111.2 kV/mm. With the increase of CB content, breakdown strength of the compound structure of CB/LDPE/EVA semi-conductive layer and the insulation layer increases. The work has important guiding significance for the breakdown fault analysis of submarine cable.