Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 7th Sem Old 170903 Power System Protection Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VII (Old) EXAMINATION ? WINTER 2019
Subject Code: 170903 Date: 28/11/2019
Subject Name: Power System Protection
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) What do you understand by a zone of protection? Discuss various zones of
protection for a modern power system.
07
(b) What do you understand by time multiplier setting and plug setting multiplier in
over current relay? Explain with the help of relay characteristic.
07
Q.2 (a) What is amplitude and phase comparator? What is duality between them? 07
(b) Explain difference between protective C.T. and measuring C.T. 07
OR
(b) Derive an expression for torque produced by an induction relay. Using the
expression find the necessary conditions for two alternative fluxes acting on a
rotor to produce torque and maximum torque.
07
Q.3 (a) Explain with a neat diagram the over current protection of a 3 phase feeder
against phase faults and earth faults. How many phase fault and earth fault relays
are used?
07
(b) Explain the impedance relay characteristic on the R-X diagram. Discuss the range
setting of three impedance relays placed at a particular location.
07
OR
Q.3 (a) Explain under reach and over reach of a distance relay. 07
(b) Discuss the advantages of numerical protection. 07
Q.4 (a) Explain the restricted earth fault protection scheme applicable to transformer. 07
(b) A 3 phase transformer having line voltage ratio of 400 V/ 33000 V is connected
in star-delta. The CTs on the 400 V side have a current ratio of 1000/5.
What must be the ratio of CTs on the 33000 V side?
07
OR
Q.4 (a) Explain the differential protective scheme for protection of bus-zone. 07
(b) Discuss the protection employed against loss of excitation of an alternator. 07
Q.5 (a) With the help of block diagram explain the organization of numerical relay. 07
(b) Explain installation and commissioning tests of relays in brief. 07
OR
Q.5 (a) Explain the phase comparison method of carrier current protection. 07
(b) What are various abnormal operating condition from the load side and supply
side to which an induction motor is subjected to?
07
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This post was last modified on 20 February 2020