ReviewProtection of multi-terminal and distributed DC systems: Design challenges and techniques

- Essential guidelines for the proper design of DC protective relays are presented.
- Grounding has significant impacts on the short circuit current behavior of DC system.
- Speed, complexity and power loss are important parameters of a circuit breaker.
- New wide bandgap semiconductors can highly improve the rating of circuit breakers.
- Utilization of advanced signal processing methods can result to a new protection scheme.

The DC power system is an effective architecture that achieves more reliable power with higher efficiency, leading to a better integration of energy sources with fewer power electronic converters. However, the protection of DC power systems, especially multi-source distribution systems and multi-terminal dc lines, involves many challenges. Through extensive study, this paper presents the key requirements for the protection of these systems, such as personal safety, fault detection and location capabilities, equipment survivability and ride-through capability. Various grounding topologies utilized in DC systems are detailed and their advantages and limitations are compared in terms of personal safety, transient short circuit current behavior, fault detection and protection capabilities, and insulation requirements. In multi-source systems, the proper design and coordination of circuit breakers and disconnecting switches are very important to rapidly isolate the faulted area and restore the system. In this paper, different circuit breaker technologies and configurations have been studied and their performances are compared. Moreover, this paper presents a comprehensive overview of various fault detection and location techniques suggested in the literature. The requirements and applications of these techniques are discussed and areas for future research are indicated.