Availability evaluation of Multi-Terminal DC networks with DC circuit breakers

This paper evaluates the availability of three conceptual offshore Multi-Terminal HVDC (MTDC) grids with DC circuit breakers (DC-CBs). MTDC grids can simultaneously support integration of offshore wind power plants, cross-border trade of electricity and electrification of oil&gas installations. A Reliability, Availability and Maintainability (RAM) approach has been used to analyse the systems. Discrete-event simulations are performed using Monte-Carlo techniques for random sampling. With DC-CBs, DC faults can be isolated, hence avoiding complete shutdown of the entire MTDC grid. The results show that local converter faults are the most dominant source of unavailability and that DC-CBs will only marginally increase the availability of power at the offshore nodes. On the other hand, DC-CBs will significantly increase the reliability of power. Assessing the consequences of power outages to the affected nodes and to the onshore AC power systems is therefore of utmost importance to quantify the benefit of DC-CBs.