Topside circulating current and lead sheath grounding of export cables for offshore wind

This paper is intended to raise awareness of an easily overlooked issue concerning calculating and designing for circulating sheath currents at the terminations of offshore high voltage cable systems. This experience relates to 3 core armoured submarine cables with semiconducting sheath designs. The paper highlights an end-effect which is not well described in standards, but one that can still be readily calculated. Neglecting this end-effect can lead to a non-conservative estimates of the sheath currents seen in real systems. The effect is specifically an issue for semiconducting core sheaths when combined with even a modest phase separation on the offshore substation topsides.