Corrosion of copper armor caused by induced current in a 500 kV alternating current submarine cable

Abstract

Alternating current (AC) is induced in armor because of electromagnetic induction. The induced AC flowing through the electrolyte–metal interface corrodes the armor, which accelerates submarine cable failure. Numerical simulation is performed to calculate the induced current density along a 500 kV submarine cable in the East China Sea, and the effect factors of the current are determined. Simulation experiments are conducted to study the corrosion of copper armor in artificial seawater at various AC current densities. The results reveal that the induced AC current densities can considerably increase the corrosion rates of copper armor. The max induced AC current densities are found to be located at the beginning and the end of the submarine cable. Cross-connection can effectively reduce the induced AC current density of the armor and thus reduce its corrosion rate (From 1.57 to 0.15 mm/a). Cross-connections are required at both ends of a submarine cable to reduce armor corrosion. For cross-connected submarine cables, the cable length, cable spacing, and resistivity of the outer serving have a negligible effect on the corrosion rate. The load current, defect diameter, and environmental resistivity have a considerable effect on the current density.