Table 1 Comprehensive literation review of FCLs.

^17,18,19,20

Superconducting

Involves transition from a superconducting state (zero resistance) to a resistive state when critical parameters like current density and temperature are exceeded, effectively limiting fault currents and protecting HVDC system components.

Enhances stability and reliability of HVDC systems by managing high short circuit fault currents, particularly in VSC-based MT-HVDC grids.

It incurs high costs due to the expensive superconducting materials and cryogenic cooling systems required. They also add operational complexity because of the need for precise control and monitoring of temperature and current density. Additionally, SFCLs face challenges with fault recovery times and are sensitive to external magnetic fields, temperature variations, and mechanical stresses.

SFCL effectively limits fault current in VSC-based multi-terminal HVDC systems.

SFCL reduces current transients for both AC and DC faults.

Also, SFCL integration impacts the current sizing of limiting inductors and surge arrester energy.

^21,22,23,24

Solid-State

Utilization of high inductance in conjunction with solid-state components (thyristors or IGBTs), including bridge rectifiers and reactors that may possess the ability to switch between AC and DC modes to dynamically adjust impedance and limit fault currents. Also, they offer high impedance during faults and negligible impedance during normal operation, ensuring improved system stability and reliability.

Enhances fault current management in HVDC systems, with bridge type being suitable for both AC and DC operations.

High power losses during normal operation, the necessity for careful thermal management, and the complexity of control strategies required for bridge-type FCLs, which may also experience switching overvoltages leading to high voltage stresses, are notable disadvantages.

This technology demonstrates effective fault current limitation by significantly reducing recovery times and enhancing system stability. It provides high impedance during faults while maintaining negligible impedance during normal operation, which is confirmed through extensive simulations and prototype testing. Moreover, it showcases reduced requirements for DC circuit breakers and offers effective bidirectional fault current limitations.

^25,26,27

Mechanical

It uses a combination of mechanical switches and spring-loaded actuators in the form of movable air-core spherical reactor rings to interrupt the current path at the AC zero-crossing, using an LC circuit to create zero-crossings in HVdc systems, limiting fault current rise.

Effective for both low voltage DC and AC/DC hybrid systems.

The mechanical FCL has challenges, including slow response time, wear and tear, complex design, high maintenance, integration complexity, synchronization issues, and sensitivity to external conditions.

Mechanical fault current limiters utilize magnetic fields to control arc movement within switches, effectively reducing circuit breaker load and enhancing system efficiency in HVDC systems up to 150 kV. However, further research is needed to evaluate its feasibility for voltages up to 500 kV in HVDC grids.

^28,29,30,31

Hybrid

Utilizes a hybrid combination of mechanical switches or power electronic devices to limit and interrupt fault currents.

HVDC systems, especially those with Voltage Source Converters (VSC) in multiterminal grids

Complex design and higher costs arise from the combined mechanical and electronic components, while voltage spikes during switching necessitate careful parameter selection.

Demonstrated effective fault current limitation with reduced peak currents, faster isolation, improved current-limiting capability, and reduced overvoltage stress, validated through simulations and experiments.