GTU BE 2020 Summer Question Papers || Gujarat Technological University
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GUJARAT TECHNOLOGICAL UNIVERSITY
B.E SEMESTER-VIII EXAMINATION —-SUMMER 2020
Subject Code: 2180901 Date: 26/10/2020
Subject Name: TESTING AND COMMISSIONONG OF ELECTRICAL EQUIPMENT
Time:02.30 PM TO 05.00 PM Total Marks: 70
Instructions:
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) What do you mean by polarization index with reference to small size machine
and large size machine?
is the reason for deterioration of insulation resistance?
(c) Which are different test performed on electrical equipment from
manufacturing process to commissioning process? What is their significance?
Q.2 (a) Give the connection difference between Dy1 and Dy11 for transformer.
Explain type of bushing.
(c) What are the characteristics of transformer oil? How can we improve it?
OR
(c) What are needs for drying out of transformer? Explain hot oil circulation
Q.3 (a) What are the possible reasons for vibration in D.C.Machine? Give their
remedies.
(b) Where the insulation resistance of transformer is to be measured? Why is
resistances decrease after some time?
characteristics of switching impulse.
OR
Q.3 (a) What is importance of polarity test in power transformer and current
transformer?
(c) Give the reason, why should we kept the tapping on LV side not on HV side
in some special case of transformer ?
Q4 (a) What are reasons for vibration in induction motor?
(b) What are the reasons for temperature rise in motor while carrying a rated load?
OR
Q.4 (a) What are the conditions for parallel connection of transformer?
(b) Can we connect Dy1 AND Dy11 transformer in parallel? Justify your answer.
(c) Draw the vector diagram and connection diagram for Yyo and Dpo.
ON command?
(b) How the contact resistance can be measured in circuit breaker?
(c) What are the different test performed on out-door circuit breaker?
OR
(b) Draw Yz and Yzi connection for three phase transformer.
(c) Which are the different tests performed for commissioning of transformer?
Explain any two with its significance.
FirstRanker.com
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E SEMESTER-VIII EXAMINATION —-SUMMER 2020
--- Content provided by FirstRanker.com ---
FirstRanker.comSubject Code: 2180901 Date: 26/10/2020
Subject Name: TESTING AND COMMISSIONONG OF ELECTRICAL EQUIPMENT
Time:02.30 PM TO 05.00 PM Total Marks: 70
Instructions:
--- Content provided by FirstRanker.com ---
1. Attempt all questions.2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) What do you mean by polarization index with reference to small size machine
and large size machine?
--- Content provided by FirstRanker.com ---
(b) What is the importance of insulation resistance for electrical equipment? Whatis the reason for deterioration of insulation resistance?
(c) Which are different test performed on electrical equipment from
manufacturing process to commissioning process? What is their significance?
Q.2 (a) Give the connection difference between Dy1 and Dy11 for transformer.
--- Content provided by FirstRanker.com ---
(b) Explain how the H.V bushing and L.V. Bushing installed in transformer.Explain type of bushing.
(c) What are the characteristics of transformer oil? How can we improve it?
OR
(c) What are needs for drying out of transformer? Explain hot oil circulation
--- Content provided by FirstRanker.com ---
method for drying out.Q.3 (a) What are the possible reasons for vibration in D.C.Machine? Give their
remedies.
(b) Where the insulation resistance of transformer is to be measured? Why is
resistances decrease after some time?
--- Content provided by FirstRanker.com ---
(c) How the switching impulse test performed on-transformer? Give thecharacteristics of switching impulse.
OR
Q.3 (a) What is importance of polarity test in power transformer and current
transformer?
--- Content provided by FirstRanker.com ---
(b) Why we are measuring R15 and R60 reading while measuring PI index?(c) Give the reason, why should we kept the tapping on LV side not on HV side
in some special case of transformer ?
Q4 (a) What are reasons for vibration in induction motor?
(b) What are the reasons for temperature rise in motor while carrying a rated load?
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(c) How can we find short circuit winding or short circuit bar in rotating machine?OR
Q.4 (a) What are the conditions for parallel connection of transformer?
(b) Can we connect Dy1 AND Dy11 transformer in parallel? Justify your answer.
(c) Draw the vector diagram and connection diagram for Yyo and Dpo.
--- Content provided by FirstRanker.com ---
Q.5 (a) What are the possible reasons if circuit breaker is not TURN ON if we giveON command?
(b) How the contact resistance can be measured in circuit breaker?
(c) What are the different test performed on out-door circuit breaker?
OR
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Q.5 (a) What are the methods to measure earthing resistance in sub-station?(b) Draw Yz and Yzi connection for three phase transformer.
(c) Which are the different tests performed for commissioning of transformer?
Explain any two with its significance.
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