1. What is an air-cooled transformer?
(A) A transformer that has a fan or blower to circulate air around the windings
(B) A transformer that uses air as an insulating medium instead of oil or paper
(C) A transformer that has no cooling or insulating medium at all
(D) A transformer that uses air as a cooling medium instead of oil or water
2. What is the main advantage of using an air-cooled transformer over an oil cooled transformer?
(A) An air-cooled transformer is cheaper and lighter
(B) An air-cooled transformer is safer and more environmentally friendly
(C) An air-cooled transformer is more efficient and reliable
(D) All of the above
3. What is the main disadvantage of using an air-cooled transformer over an oil cooled transformer?
(A) An air-cooled transformer has lower insulation strength and voltage rating
(B) An air-cooled transformer has higher losses and noise level
(C) All of the above
(D) An air-cooled transformer has lower thermal capacity and overload capability
4. What is the most common cause of overheating fault in a transformer?
(A) All of the above
(B) Radiator is not clean
(C) Overcurrent
(D) Cooling fans are not working properly
5. What is the effect of earth fault on a Y-connected winding with neutral point connected to ground through an impedance Zg?
(A) The fault current depends on Zg and is inversely proportional to the distance of the fault from the neutral point
(B) The fault current depends on Zg and is proportional to the distance of the fault from the neutral point
(C) The fault current does not depend on Zg or the distance of the fault from the neutral point
(D) The fault current does not depend on Zg but depends on the distance of the fault from the neutral point
6. What is the cause of interturn faults in a transformer?
(A) Tank faults due to oil leakage
(B) Core faults due to insulation breakdown
(C) Phase-to-phase faults due to short circuits
(D) Winding flashovers caused by line surges
7. What is the effect of tank faults resulting in loss of oil in an oil cooled transformer?
(A) Both A and B
(B) Abnormal temperature rise
(C) Reduced winding insulation
(D) Neither A nor B
8. What are some of the protection methods used for transformer faults?
(A) Overcurrent relay with under-voltage blocking
(B) Zero sequence protection
(C) All of the above
(D) Negative sequence protection
9. What is a 3-phase power transformer?
(A) A transformer that has three primary windings and one secondary winding that are connected in either star or delta configuration
(B) A transformer that has one primary winding and three secondary windings that are connected in either star or delta configuration
(C) A transformer that has three primary windings and three secondary windings that are connected in either star or delta configuration
(D) A transformer that has one primary winding and one secondary winding that are connected in either star or delta configuration
10. What is an oil cooled transformer?
(A) A transformer that uses oil as an insulating medium instead of paper or gas
(B) A transformer that uses oil as a cooling medium instead of air or water
(C) A transformer that has no cooling or insulating medium at all
(D) A transformer that has a radiator or heat exchanger to circulate oil around the windings
11. What is the main advantage of using an oil cooled transformer over an air-cooled transformer?
(A) An oil cooled transformer has higher insulation strength and voltage rating
(B) All of the above
(C) An oil cooled transformer has higher thermal capacity and overload capability
(D) An oil cooled transformer has lower losses and noise level
12. What is the main disadvantage of using an oil cooled transformer over an air-cooled transformer?
(A) An oil cooled transformer is more expensive and heavier
(B) An oil cooled transformer is less safe and more environmentally harmful
(C) An oil cooled transformer is more difficult to maintain and repair
(D) All of the above
13. What is the most common cause of overheating fault in a transformer?
(A) All of the above
(B) Radiator is not clean
(C) Overcurrent
(D) Cooling fans are not working properly
14. What is the effect of earth fault on a Y-connected winding with neutral point connected to ground through an impedance Zg?
(A) The fault current does not depend on Zg or the distance of the fault from the neutral point
(B) The fault current depends on Zg and is inversely proportional to the distance of the fault from the neutral point
(C) The fault current depends on Zg and is proportional to the distance of the fault from the neutral point
(D) The fault current does not depend on Zg but depends on the distance of the fault from the neutral point
15. What is the cause of interturn faults in a transformer?
(A) Winding flashovers caused by line surges
(B) Core faults due to insulation breakdown
(C) Phase-to-phase faults due to short circuits
(D) Tank faults due to oil leakage