00EXAM15_B_Transformer oil COURSE – Master level EXAM

Transformer oil course - Master's level EXAM

1. How (by which chemical reaction) do inhibitors prevent the oxidation of oil?

A. By forming complexes with oil

B. By quenching free radicals

C. By eliminating unstable molecules

D. By reducing induction time

2. What is the general chemical class of passivators?

A. Phenolic

B. Amino

C. Benzotriazole derivatives

D. Phosphate esters

3. What is the most significant undesirable side effect of adding passivators?

A. They promote oxidation of oil

B. They increase Tan delta of oil

C. They cause stray gassing of oil

D. They increase electrostatic charging tendency of oil

4. What are the triggers for using ester liquids in place of mineral oil?

A. Fire safety due to K class, Biodegradability and enhancing paper life

B. Better heat dissipation due to higher thermal conductivity

C. Higher dielectric strength

D. Lower Power loss

5. What is the criteria for a liquid to be classified as readily biodegradable, according to 301B?

A. The liquid should biodegrade 100% in 10 days

B. The liquid should undergo 60% degradation in 10 days, and in 28 days undergo >80% degradation

C. The liquid should degrade 100% in 28 days

D. The liquid should undergo degradation to 100% in 60 days.

6. How is aqua toxicity for fish defined as per OECD 203?

A. LD50 should be >100ppm of ester oil

B. LD50 should be >200ppm of ester oil

C. No fish should die at 100ppm of ester oil in water

D. 10% of fish population of fish would die at 100ppm of ester oil

7. What is the approximate solubility of water in Natural ester and synthetic ester @20°C?

A. Around 1100 and 2600ppm respectively

B. Around 500 and 1000 ppm respectively

C. Around 100 and 500ppm respectively

D. Around 1500 and 2600ppm respectively

8. What is the cause of electrostatic charging tendency in transformer oils?

A. Low Resistivity

B. High Power loss factor

C. It is caused by electrical double layer formation between the solid insulation and the oil

D. Low dielectric strength

9. Rank the oxidation stability of the oils – Mineral oil, Synthetic ester, Silicone Oil, Natural ester by RBOT test

A. Silicone Oil > Synthetic ester > Mineral Oil > Natural ester

B. Mineral Oil > Synthetic Ester > Silicone Oil > Natural ester

C. Synthetic ester > Silicone oil > Mineral Oil > Natural ester

D. Silicone Oil > Mineral Oil > Synthetic ester > Natural ester

10. What is the thermal class of TUK paper/Ester liquid insulation system according to IEC 60076-14?

A. 130°C

B. 150°C

C. 140°C

D. 145°C

11. Why does a rapid drop in temperature cause the BDV of Oil to become low?

A. Oil gets supersaturated with water before water could migrate to paper

B. There is free water formation

C. Ice formation takes place

D. Bubbles forms

12. What is the major advantage of Capacitive sensor in a transformer?

A. Measurements may be done online and wetness of insulation determined without delay

B. More accurate than Karl-Fischer method or columeter

C. Cost saving

D. Easy to measure

13. How is a hysteresis loop used to interpret paper wetness?

A. The broader the loop, the greater the paper wetness

B. The narrower the loop, the greater the paper wetness

C. The RS values are taken as an indication of paper wetness

D. None of the above

14. What are the ideal conditions for stray gassing in mineral oil?

A. Uninhibited oil and thermal fault

B. Free breathing

C. Overloading

D. High temperature

15. Justify the statement that life of a transformer is considered as equal to the life of paper insulation.

A. Paper has better dielectric strength than Oil

B. The statement is not true

C. Once paper life is finished, its mechanical properties deteriorate and hence the windings cannot be held in place leading to insulation failure

D. Once paper life is finished, it will deteriorate oil further leading to total insulation failure

16. What is the major factor affecting 2-FAL levels with DP of paper?

A. Type of paper affects the correlation

B. Changes in design of transformer affects correlation

C. Changes in loading transformer affect correlation

D. Partition effects of 2-FAL distribution between paper and oil are influenced by moisture and temperature

17. What is the major difference between Furan and Methanol as chemical markers?

A. Furan ppm in oil needs sample temperature correction, but methanol does not need

B. Furan ppm needs correction for water ppm present in oil; methanol does not need

C. Methanol is a marker for early-stage paper degradation; Furan is good only for later stage degradation of paper

D. Furan is more difficult to analyze compared to Methanol

18. High affinity of Ester liquids for Moisture is…

A. Bad for a transformer because it will increase water content in the oil in a transformer

B. Bad for a transformer because it will increase moisture on paper insulation

C. Good because it will keep moisture in bound form within its structure

D. Good because one can exploit the unique chemistry between water, paper and Ester liquid to maintain the paper insulation dry

19. Arrange the following faults in the increasing order of energy requirement. Partial discharge, D2, D1, T3, PD, S(Stray Gassing), and Cold Plasma

A. Cold Plasma > D2 > PD> T3 > S > D1

B. Cold Plasma > PD > S > T3 > D1> D2

C. Cold Plasma > PD > S > T3 > D2 > D1

D. Cold Plasma > PD > T3 > S > D2 > D1

20.What are the two key benefits of using Nanofluids?

A. Permittivity increase

B. Decrease of Power loss factor

C. Increase in paper life

D. Increase in heat dissipation property and BDV

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00EXAM15_B_Transformer oil COURSE – Master level EXAM

00EXAM15_B_EXAM_MASTER_Transformer oil course

Transformer oil course - Master's level EXAM