A buchholz will operate in a transformer whenever there is

• A. over load
• B. any of the above
• C. large internal fault
• D. saturation of magnetic circuit

Answer: (C)

saftey device mounted on oil filled transformer.
give protection against internal fault in transformer winding.
test of relay : 1. leakage test 2. Electrical test 3. Functional test
this relay can detect only when the oil level is below
least operating time of relay is 0.1 sec.