1. Protection of transformer against all internal faults
2. Protection of transformer against all external faults
3. Protection of transformer against both internal and external faults
4. Protection of Induction motors
Protection of transformer against all internal faults
1. All breakers
2. bulk oil breakers
3. minimum oil breakers
4. air blast circuit breakers
air blast circuit breakers
1. 25 A
2. 15 A
3. 50 A
4. 10 A
10 A
1. Earth faults
2. phase faults
3. open circuit faults
4. none of these
phase faults
1. Reduces the short circuit current
2. Improves system stability
3. Decreases system stability
4. Increases the short circuit current
Improves system stability
1. Magnetizing inrush current
2. Unbalanced operation
3. Lightning
4. Switching over voltage
Switching over voltage
1. Dangerously high voltage might develop across the secondary
2. The ferromagnetic core may develop residual magnetism
3. The reflected impedance may prevent the flow of current in the primary circuit
4. None of these
Dangerously high voltage might develop across the secondary
1. Primary protection
2. Back up protection
3. Simultaneous protection
4. Remote protection
Primary protection
1. mho relay
2. reactance relay
3. impedance relay
4. all are equally affected
impedance relay
1. 1 Volt
2. 1.25 Volts
3. 2.5 Volts
4. 4 Volts
2.5 Volts