What is Directional Relay? – Circuit Diagram, Working | Poly Notes Hub

What is Directional Relay? – Circuit Diagram, Working | Poly Notes Hub

In the field of power system protection, directional relays play a vital role in maintaining stability and detecting faults efficiently. Unlike ordinary relays, a directional relay can identify not only the presence of a fault but also its direction of flow, ensuring that protection devices operate selectively.

In this article, we’ll discuss the directional relay working principle, circuit diagram, construction, and applications in detail.

🔗 Read the complete detailed article here: What is Directional Relay? - Circuit Diagram, Working | Poly Notes Hub

What is a Directional Relay?

A directional relay is a type of protective relay that operates only when the fault current flows in a specified direction. This feature helps distinguish between forward and reverse faults in the system.

It is especially useful in parallel feeders, ring mains, and interconnected systems where current can flow in multiple directions depending on system conditions.

Working Principle of Directional Relay

The working principle of a directional relay is based on the phase angle between the voltage and current at the relay location.

When a fault occurs, the relay measures the phase displacement between these quantities. If the phase angle corresponds to the preset tripping direction, the relay operates; otherwise, it remains inactive.

Circuit Diagram of Directional Relay

The directional relay circuit diagram typically includes:

• A potential transformer (PT) for voltage measurement
• A current transformer (CT) for current detection
• A comparative device (e.g., induction cup or static comparator)

The PT and CT outputs are fed to the relay’s comparator, which determines whether the torque generated corresponds to the correct direction.

Final Thoughts

A directional relay is an essential component in modern power system protection. By detecting the direction of fault current, it ensures that only the appropriate section of the system is isolated, enhancing both safety and efficiency.

For an in-depth explanation with diagrams and examples, visit:
👉 What is Directional Relay? - Circuit Diagram, Working | Poly Notes Hub