Question

Which of the following types of faults does a bus differential relay NOT effectively detect?

• A. Busbar fault between feeders
• B. Open-circuit fault on one feeder
• C. Internal fault within a connected transformer
• D. Unbalanced current on the busbar

Hint:

Bus differential relays protect the busbar and feeders, but for transformer protection, a separate differential relay is used to detect internal faults.

Answer 1

The Correct Option is C

Bus differential relays are primarily designed to protect the busbar and its feeders. They are effective in detecting faults between feeders, open-circuit faults, and unbalanced currents. However, they are not effective at detecting internal faults within a connected transformer. For transformer protection, specialized differential protection relays are used. Thus, the correct answer is Internal fault within a connected transformer.