Power System Protection Quiz-II

The relay with inverse time is

• Directly proportional to the square of fault current

• Direct proportional to the of fault current

• Inversely proportional to the of fault current

• Inversely proportional to the square of fault current

When the fault current is 2000 A, for a relay setting of 50% with CT ratio 500/5, the plug setting multiplier will be

• 16

• 12

• 4

• 8

A Buchholz relay is used for

• Protection of a transformer against all internal faults.

• Protection of a transformer against external faults.

• Protection of a transformer against both internal and external faults.

• Protection of induction motors.

If the fault current is 2000 amps, the relay setting 50% and the C.T. ratio is 400/5, then the plug setting multiplier will be

• 25

• 45

• 50

• none of the above

If the fault current is 3000 A for a relay with a plug setting of 50% and CT ratio of 1000 : 1, the plug setting multiplier would be

• 1.5

• 3

• 4.5

• 6