Compact construction has become a development trend for flexible direct current converter stations. High-voltage cables in cable interlayers are arranged more tightly

resulting in an increasingly complex electromagnetic environment and a higher risk of abnormal discharge and heating faults. Therefore

the abnormal discharge and heating phenomena of 500 kV high-voltage cables in a flexible direct-current converter station in China are taken as the research object. A cable electromagnetic-thermal coupling simulation and analysis method considering abnormal harmonics is proposed. A cable electromagnetic-thermal coupling simulation model under graphite conductive coating (GCC) conditions is constructed. Based on the field-circuit coupling theory

abnormal discharge and heating under multiple grounding points on the GCC are simulated

the main causes of the engineering phenomena are clarified

and a multi-point grounding mitigation design with optimized GCC coating thickness is then developed. The results show that abnormal harmonic contents in the line and additional grounding points on the GCC are the main causes of abnormal discharge and heating in the cable. The maximum GCC interference voltage of the faulty-phase cable reaches 461.30 V

and the maximum cable temperature reaches 149.94 ℃. After the mitigation design

the GCC interference voltage of the faulty-phase cable decreases by 62.25%

and the maximum cable temperature decreases by 73.52%. The research results can provide a useful reference for simulation and mitigation of cable abnormal discharge and heating phenomena in engineering applications.