Specifications

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3. Drying process can be quickened by applying
A) Heat B) Hot air C) High pressure D) Vacuum.
4. A simple and quick way of checking moisture in transformer oil is
A) Crackle test B) Di-electric test C Break down test D) Flash test
5. A gap of ________________ mm is maintained between the spheres in the dielectric strength
testing kit.
A) 1 mm B) 2.5 mm C) 4 mm D) 10 mm
6. The dielectric strength of oil should be ________________ kV for 1 min. under normal
condition of oil.
A) 40 B) 100 C) 25 D) 32
7. Which relay may some times operate causing triping circuit breaker during transformer
switch ON
A) over current relay B) bucholz C) differential relay D) earth fault relay
8. Tripping of __________________ relay requires careful investigation, since it is operated
by gas evolved within the transformer.
A) over current B) under voltage C) earth fault D) bucholz
9. Transformer oil needs to be replaced if _____________________ of oil is very high.
A) dielectric strength B) moisture C) acidity D) density
10. __________________ of oil can be done even when transformer is in service.
A) changing B) purification C) draining D) inclusion
Part - B
Answer the following questions in one or two words (1 Mark)
1. Which material is best suited for gaskets for Transformer?
2. What is time normally taken for drying out a large transformer?
3. Under what conditions drying of transformer can be done by blowing in hot air through the
transformer tank?
4. What should be inlet air temperature in the above case?
5. What is IS standard (No.) which gives the specifications for transformer oil?
6. What should be colour of a good quality Transformer oil?
7. What affects the di-electric strength of Transformer oil?
8. What are the two main causes of oxidation of the oil?
9. State whether the breakdown values (BDV) are given normally refer to the RMS voltage or
peak voltage?