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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- VIII (New) EXAMINATION — WINTER 2019
Subject Code: 2180901 Date: 29/11/2019
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Subject Name: Testing and Commissioning of Electrical Equipments
Time: 02:30 PM TO 05:00 PM Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1 (a) Why the earthing resistance is kept minimum for safety of human being? What is the effect if earthing resistance is high? [03]
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(b) Explain three point method for measurement of earthing resistance [04]
(c) Which type of test is conducted on electrical equipment during its manufacturing process? [07]
Q.2 (a) What are the steps taken while installation of electrical equipment at site? [03]
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(b) Which care must be taken when new transformer is dispatched on site from a factory? [04]
(c) Explain how the transformer group DY1 and DY11 is to be tested. [07]
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OR(c) Explain step of drying out of big size of transformer. [07]
Q.3 (a) Why the shaft alignment is required for switch gear installation and motor installation? [03]
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(b) How the winding resistance of transformer is to be measured? [04](c) How the switching impulse test and high voltage test is conducted by transformer? [07]
OR
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Q.3 (a) How the ratio test is conducted on transformer? [03]
(b) How the insulation resistance is measured in transformer? [04]
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(c) Why the tape changer is kept of HV side of transformer? Give your justification? [07]Q.4 (a) What are reasons for vibration in induction motor? [03]
(b) What are the reasons if D.C motor does not start on giving a rated voltage? [04]
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(c) What are the different methods for drying of rotating machine? [07]OR
Q.4 (a) How block rotor and open circuit test is conducted on induction motor? Which parameters can we obtained from this test? [03]
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(b) How the temperature rise test is conducted on rotating machine? [04]
(c) How the PI is measured of rotating machine? What is the significance of it on performance of rotating machine? [07]
Q.5 (a) Which are the tests conducted on circuit breaker? [03]
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(b) What is the reason if circuit breaker is refused to close if closing signal is given? [04]
(c) Explain closing and opening mechanism in circuit breaker [07]
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ORQ.5 (a) What is step and touch potential in substation? What is its significance? [03]
(b) What is the preferred location of lightning arrester in substation? Give your justification. [04]
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(c) Which are different components of sub-station? What are the functions of each component in sub-station? [07]
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