Overall availability assessment of HVDC VSC XLPE cable symmetrical monopolar configuration

This paper focuses on the employment of analytical methods for reliability/availability assessment of HVDC-VSC point-to-point connections. In particular, underground XLPE cable links are investigated and an exemplificative calculation for a typical layout is carried out. Key reliability features of state-of-the-art modular multilevel converters (MMC) are highlighted. Closed-form reliability equations, fitting to the operative characteristics of two widespread alternative converter configurations for HVDC transmission, are utilized. After an initial overview of significant reliability issues concerning major equipment making up the link, basic strategies for reaching target levels of reliability and availability in critical connections of this kind, is expounded.