Which relay is specifically designed to operate based on uneven current distribution?

• A. Distance relay
• B. Overvoltage relay
• C. Differential relay
• D. Current relay

Answer: (C)

The differential relay is specifically designed to operate based on uneven current distribution, making it effective for protecting electrical circuits and equipment from faults. This type of relay monitors the difference in current between two or more circuits. In a healthy system, the current entering a section of the system will equal the current exiting that section. However, if there's a fault (such as a short circuit) within the monitored area, the currents will be unbalanced, causing the differential relay to detect the discrepancy. Upon sensing this uneven distribution, the relay will initiate protective measures, such as disconnecting the faulty circuit.

This ability to compare input and output current makes the differential relay particularly valuable in applications like transformer and busbar protection, where maintaining balance in current flow is critical for safe operation. The prompt response to imbalances minimizes damage to equipment and enhances system reliability.