What is directional relay and its advantages and disadvantages?

A directional relay is a type of protective relay that determines the direction of fault current flow in a power system, enabling it to operate only when a fault occurs in a specific direction. Advantages include improved protection for transmission lines and the ability to distinguish between faults and load conditions, enhancing system reliability. However, disadvantages include increased complexity in settings and coordination, as well as the possibility of misoperation if the directional settings are not correctly configured. Additionally, directional relays can be more costly compared to non-directional relays.