GTU BE 8th Semester 180903 Power System Practice and Design Summer 2018 Question Paper

1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE – SEMESTER ?VIII (old) – EXAMINATION ? SUMMER 2018
Subject Code:180903 Date:02/05/2018
Subject Name:Power System Practice and Design
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) Discuss classification of distribution systems with neat diagrams. What are the
advantages and dis-advantages of each?
07
(b) Enlist the steps to be followed for the construction of receiving end and
sending end power circle diagram. How the losses are determined from
receiving end diagram?

07

Q.2 (a) Define critical disruptive voltage and visual critical voltage. How Corona los can
be determined? What is significance of Corona in the design of transmission
line?
07
(b) Determine ABCD constants and Regulation of 3-phase Transmission line
considering following data.
Power = 85,000 kW, p.f.= 0.9 lagging, Distance = 160 km, Voltage = 230 kV,
Spacing of conductors = 10.2 m , Resistance/km = 0.22 O, outer radius R = 0.827
cm, Self GMD =0.768 R.
07
OR
(b) A single phase a.c. distributor 500 m long has a total loop impedance of (0.02 +j0.04) O and is fed from one end at 250 V. It is loaded as under:
1. 50 A at unity power factor, 200 m from the feeding point.
2.100 A at 0.8 power factor lag, 300 m from the feeding point.
3. 50 A at 0.6 power factor lag, at the far end.
Calculate the total voltage drop in the distributor and the voltage at the far end.
07

Q.3 (a) State and explain Kelvin?s law for the most economical cross section of
conductor.
07
(b) The cost of two core feeder cable, including installation is (90a +10) per metre
& interest and depreciation charges are 15%. The cable 1 km in length and cost
of energy is 3 paisa per unit. Maximum current in the feeder is 260 A and
demand is such that copper loss is equivalent to that would be produced by full
current flowing for 6 months. If resistance of conductor of 1 sq. cm. and 1 km
length is 0.173 ohm. Calculate most economical cross sectional area.
07
OR
Q.3 (a) What is lamp flicker? What are its causes? What type of loads are responsible for
it? How can it be reduced?
07
(b) Explain the steps involve in the lightning arrestor selection. Highlight the effect of
earthling for selecting voltage rating of the arrestor.
07

Q.4 (a) Define Insulation Coordination. Explain Insulation Co-ordination curves. 07
(b) What methods are adopted to reduce the tower footing resistance. 07
OR
Q.4 (a) What is stringing chart ? How the preliminary design of tower is carried out?
07
(b) Discuss applications of HVDC systems 07

Q.5 (a) Write a brief note on Gas Insulated Substation
07
(b) Explain the various types of DC link. Name some HVDC systems in India and its
Future.
07

1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE – SEMESTER ?VIII (old) – EXAMINATION ? SUMMER 2018
Subject Code:180903 Date:02/05/2018
Subject Name:Power System Practice and Design
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) Discuss classification of distribution systems with neat diagrams. What are the
advantages and dis-advantages of each?
07
(b) Enlist the steps to be followed for the construction of receiving end and
sending end power circle diagram. How the losses are determined from
receiving end diagram?

07

Q.2 (a) Define critical disruptive voltage and visual critical voltage. How Corona los can
be determined? What is significance of Corona in the design of transmission
line?
07
(b) Determine ABCD constants and Regulation of 3-phase Transmission line
considering following data.
Power = 85,000 kW, p.f.= 0.9 lagging, Distance = 160 km, Voltage = 230 kV,
Spacing of conductors = 10.2 m , Resistance/km = 0.22 O, outer radius R = 0.827
cm, Self GMD =0.768 R.
07
OR
(b) A single phase a.c. distributor 500 m long has a total loop impedance of (0.02 +j0.04) O and is fed from one end at 250 V. It is loaded as under:
1. 50 A at unity power factor, 200 m from the feeding point.
2.100 A at 0.8 power factor lag, 300 m from the feeding point.
3. 50 A at 0.6 power factor lag, at the far end.
Calculate the total voltage drop in the distributor and the voltage at the far end.
07

Q.3 (a) State and explain Kelvin?s law for the most economical cross section of
conductor.
07
(b) The cost of two core feeder cable, including installation is (90a +10) per metre
& interest and depreciation charges are 15%. The cable 1 km in length and cost
of energy is 3 paisa per unit. Maximum current in the feeder is 260 A and
demand is such that copper loss is equivalent to that would be produced by full
current flowing for 6 months. If resistance of conductor of 1 sq. cm. and 1 km
length is 0.173 ohm. Calculate most economical cross sectional area.
07
OR
Q.3 (a) What is lamp flicker? What are its causes? What type of loads are responsible for
it? How can it be reduced?
07
(b) Explain the steps involve in the lightning arrestor selection. Highlight the effect of
earthling for selecting voltage rating of the arrestor.
07

Q.4 (a) Define Insulation Coordination. Explain Insulation Co-ordination curves. 07
(b) What methods are adopted to reduce the tower footing resistance. 07
OR
Q.4 (a) What is stringing chart ? How the preliminary design of tower is carried out?
07
(b) Discuss applications of HVDC systems 07

Q.5 (a) Write a brief note on Gas Insulated Substation
07
(b) Explain the various types of DC link. Name some HVDC systems in India and its
Future.
07

2

OR
Q.5 (a) What are the limitations of HVAC transmission? Give the applications of HVDC
system.
07
(b) What is earth resistance ?Why its value should be as low as possible ?How it is
measured with voltmeter-ammeter method ?
07
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