Question

Back on protection is used to protect:
1. Over voltage
2. Over current
3. Transient current
4. Short circuit

Answer 1

Correct Answer - Option 4 : Short circuit

Back up protection:

• The backup protection provides the backup to the main protection during a short circuit whenever it fails in operation or is cut out for repairs.
• The backup protection is essential for the proper working of the electrical system.
• The backup protection is the second line of defense which isolates the faulty section of the system in case the main protection fails to function properly.
• The failure of the primary protection occurs because of the failure of the DC supply circuit, current, or voltage supply to the relay circuit.
• The backup protection may be provided either on the same circuit breaker which would be formally opened by the main protection or in the different circuit breaker.
• The backup protection is mainly used where the main protection of the adjacent circuit is unable to back up the main protection of the given circuit.
• The use of backup protection depends on economics and technical consideration.
• The backup protection is usually for economic reasons not so fast as the main protection.​