Ensuring that the DC voltage remains within an acceptable range is a major concern for HVDC systems.

The Modular Multilevel Converters (MMCs) have emerged as the most suitable converter technology for HVDC application.

A protection strategy for high voltage direct current grids using superconducting fault current limiters as main protection component is presented in this work.

A protection strategy for multi-terminal HVDC (MTDC) grids based on AC/DC converters without fault blocking capability such as half-bridge MMC converters is presented in this paper.

Mainly used in AC grids, resistive type superconducting fault current limiters may be still more interesting for DC systems due to their capability to reduce high short circuit currents appearing in case of DC cable fault. This limiter reduces the breaking capability, speed, and energy requirements of the required DC circuit breaker allowing the implementation of electro mechanical breakers for fault current interruption. These breakers have lower breaking capability, on load losses, and investment costs in comparison with hybrid circuit breakers based on power electronics. This paper presents a technical and economic analysis of a superconducting fault current limiter used in a radial three terminal high voltage DC grid to protect a cable link. Based on simulation studies using an electro magnetic transient program, an effective system protection will be demonstrated with special attention to the continuity of power flow through healthy parts of the grid.