Analysis of An Accident Caused by Current Mismatch in The Grounding Structure of A High-Voltage Single-Core Submarine Cable

With the expanding scale of offshore wind farms construction, the demand for submarine cables is increasing. As an important carrier of power transmission, the operation reliability of submarine cables line has also become a research focus. In the past, the research focus of the grounding structure is mainly on the cable flow control, little attention is paid to the submarine cable accessory electrical accidents caused by the improper grounding structure. In this paper, a case of 220kV marine cable breakdown was analyzed, which is thought caused by local overheating fault of sheath grounding structure. Based on the electromagnetic transient simulation software ATP- EMTP, the current distribution of sheath and armour structure under the condition of good grounding and bad contact was studied. The results show that the grounding current distribution is mainly affected by the ratio of sheath/armour grounding circuit resistance. Based on the field practice, a simulation model of grounding defects is built, which verifies that the improper grounding of armour and the damage of semi-conductive layer are the main reasons for the increase of sheath grounding current.