In a directional comparison blocking (DCB) scheme, why is a communications signal transmitted?

In a directional comparison blocking (DCB) scheme, a communication signal is transmitted specifically to indicate that a fault is in the reverse direction. This type of protection scheme is commonly used in electrical transmission lines and helps in determining the fault's location based on the direction of the fault current. By transmitting a signal that communicates whether a fault is detected in the opposite direction, the system can effectively block unwanted tripping of protection devices that may otherwise activate erroneously.

This communication helps operators to enhance system reliability by ensuring that only the necessary protections operate in response to actual conditions, minimizing disruption in case of transient faults or conditions where the fault is actually beyond the terminal units. Hence, the primary function of transmitting a signal in the DCB scheme revolves around accurately determining and communicating the directionality of a fault to facilitate correct decision-making in protection protocols.