Condition monitoring of HVDC transmission systems for offshore wind

The work presented in this paper reviews the methods of detecting PD in a HVDC system. The behavior of PD under DC conditions for common defects types is discussed. The partial discharges studied in this paper are limited to three dielectric samples with discharges from well-defined discharge sites. These include corona, surface discharges and internal voids. The samples were subjected to AC and DC excitation, AC excitation as a sense check to ensure the samples yield the expected PD activity. A further area of investigation was the application of analysis techniques to enable the identification of the type of PD event. The ability to determine the type of PD apparent in the HVDC system feeds directly into the condition monitoring of the HVDC system and identification of the insulation fault.