Statement: Which relay provide signal before the serious fault:
- Overcurrent relay
- Buchholz relay
- Undercurrent relay
- All of above
Correct answer: 2. Buchholz relay
Also read: Working of Protection Relays
In case of the occurrence of incipient faults in transformers, the generated hydrogen gas tries to go into the conservator and gets entrapped in the relay chamber. When a sufficient amount of gas is accumulated, it exerts pressure on float thus sending an alarm. Therefore a Bucholz relay provides a signal in case of incipient fault and is a relay that provides a signal before the occurrence of a serious fault.