ABSTRACT
High Voltage Direct Current (HVDC) transmission systems are always vital elements of the national power grids they form part of. In consequence, the operational availability of HVDC transmissions is a matter of great concern, and an increasing current trend is to put high and very specific availability requirements on new transmissions. The paper describes the methodology used in ABB HVDC projects in order to assure high availability and reliability of the plants to be delivered. A series of analyses are performed dealing with formal availability as well as with maintenance planning and spare parts planning; these analyses combine to verify and assure that the given availability guarantees can be met.
