This thesis deals with the online measurement of partial discharge (PD) in a high-voltage direct current (HVDC) converter station. The HVDC station is a particularly challenging environment for PD measurement due to elevated interference levels caused from the switching of the thyristor-controlled converters. Online PD measurements are performed on two specimens, one is an HVDC converter transformer and the other an HVDC converter wall bushing. The measurements are performed in the high-frequency range between 400-kHz to 30-MHz with a modern PD measurement instrument that employs a signal processing technique known as feature extraction. The results demonstrate that online measurement of PD in an HVDC station environment is possible. Input filtering and feature extraction methods can mitigate the converter interference. The feature extraction methods can also isolate individual PD phenomena, and allow for the trending and monitoring of insulation degradation. Furthermore, specific strategies for PD measurement and analysis are developed.