Electric power in the twenty-first century is no longer what it used to be. Apart from meeting the growing demand, a strong push to produce electricity in an economically sound way and at the same time environmentally friendly manner without adding carbon footprint has taken the conventional power system in a new direction. Recent years have seen tremendous interest in transmitting bulk amounts of power using the dc system.

High voltage direct current system, or commonly known as HVDC, is one of the key technologies in this trajectory. Implementation of the HVDC system is made possible by the advancement of power electronics, namely power converters which convert the ac to dc and vice versa. The converter technologies employed in the present HVDC system can be broken into two types: current source converter (CSC) and voltage source converter (VSC). The inception of the CSC dates back to the 1970s. Then, the VSC came along in the 1990s. DC system also offers numerous benefits, for example, being economical for long-distance transmission, flexibility in control and enabling integration of renewable energies, particularly wind and solar. Besides the HVDC-based long-distance bulk power transmission, dc systems are also being considered for microgrids, datacentre, more-electric aircraft, shipboard power systems, etc. in the medium-and low-voltage dc (MVDC and LVDC) power distribution domains. One of the most important and critical challenges is the fault analysis and design of the protection system to safeguard such a dc grid against network faults. For the ac grid, the circuit-breakers (CB), protective relays, and the protection standards are well established, which are not quite mature for the dc grid. This is mainly because over the last century, we have mainly relied on the ac power systems. Protection systems for the ac power systems do not always conform to the dc systems, as the nature of the dc fault transient is fundamentally different from that of the ac system. This book is a comprehensive reference guide on the important topic of dc grid protection design. It bridges a much-needed research gap to enable wide-scale implementation of energy-efficient dc grids in the near future. This book looks into dc grid architecture, operation, control along with rigorous fault analysis and design