Fourth Semester B.Tech. Degree Examination, December 2009
(2003 Scheme)
03.406 : POWER SYSTEM ENGINEERING – I (E)
Time : 3 Hours Max. Marks : 100
PART – I
Answer all questions.
1. What is the need for transposition of overhead lines ?
2. What are the advantages of bundled conductors ?
3. Explain the concepts of GMD and self GMD.
4. Describe the reasons for grading of cables.
5. Write brief notes on sag template and stringing chart.
6. What is meant by string efficiency and how can it be improved ?
7. How do the load factor and diversity factor influence the cost of generation ?
8. What are the requirements of an ideal traction system ?
9. Discuss the merits and demerits of direct electric arc furnace.
10. Distinguish between electric arc welding and resistance welding. (10×4=40 Marks)
PART – II
Each question carries 20 marks.
Module – I
11. a) Derive from first principles, the capacitance per km to neutral of a 3-phase
overhead transmission line with unsymmetrical spacing of conductors.
b) Calculate the chraging current of a 3-ph, 50 Hz, 33 KV, 3 conductor overhead
transmission line, 10 Km long, having conductor dia 20 mm, spaced 2.5 ms, at
the corners of an equilateral triangle.
OR
12. a) Explain the significance of using per unit system in power system analysis.
b) A 3-ph, 220 KV, 50 Hz transmission line, 200 Km long transmits a load of
75 MW at 0.8 p.f. lagging at the receiving end. Resistance of the line/ph/km =
0.8 ohm, susceptance/ph/km = 6 ?? 10–6 mho, Reactance/ph/km = 0.8 ohm.
Determine :
a) the ABCD constants of the line and
b) sending end voltage and current
Module – II
13. a) Describe the various systems of power transmission and compare the conductor
material (volume) for 3-ph, 3 wire a.c. with that of 3 wire d.c. State the assumptions
made.
b) A 33 KV, 3-ph, underground cable, 4 km long uses three single core cables.
Each of the conductors has a diameter of 2.5 cm and the radial thickness of
insulation is 0.5 cm. The relative permitivity of the dielectric is 3.0. Determine (a)
the capacitance of the cable/ph and (b) charging current/ph.
OR
-3- 8075
14. a) Explain briefly about the various conductor materials used for overhead lines.
Give their relative advantages and diadvantages.
b) Find the disruptive critical voltage and visual critical voltage (for local and general
corona) for a 3-ph line having 1 cm dia conductors, spaced in 3 m delta
arrangement. Assume temperature 26°C, pressure 74 cm of mercury, surface
factor 0.85 and irregularity factor for local visual corona 0.72 and general visual
corona 0.82.
Module – III
15. a) What are the causes of low power factor in an electrical system and discuss the
methods for improving the power factor ?
b) A consumer takes a steady load of 300 KW at a lagging p.f. of 0.7 for
3000 hours in a year. The tariff is Rs. 130/KVA of M.D. annually and 4 paise per
KWh. The annual cost of phase advancing plant is Rs. 13.00 per KVAR.
Determine the annual saving, if the p.f. of the load is improved to 0.9.
OR
16. a) What is specific energy consumption ? Explain the factors that affect the specific
energy consumption of a train operating at given scheduled speed.
b) The average distance between stops on a level section of railway is 1.5 Km. The
train weighing 200 tonnes has a scheduled speed of 32 km/hr, the duration of the
stops being 25 sec. The acceleration is 1.9 km/hr/sec and braking retardation is
3.2 km/hr/sec. Train resistance to traction is 40 Nw/tonne. Allowance for rotational
inertia is 10%. Calculate the specific energy output in watt hours per tonne km
for the run. Assume trapezoidal speed-time curve.
(2003 Scheme)
03.406 : POWER SYSTEM ENGINEERING – I (E)
Time : 3 Hours Max. Marks : 100
PART – I
Answer all questions.
1. What is the need for transposition of overhead lines ?
2. What are the advantages of bundled conductors ?
3. Explain the concepts of GMD and self GMD.
4. Describe the reasons for grading of cables.
5. Write brief notes on sag template and stringing chart.
6. What is meant by string efficiency and how can it be improved ?
7. How do the load factor and diversity factor influence the cost of generation ?
8. What are the requirements of an ideal traction system ?
9. Discuss the merits and demerits of direct electric arc furnace.
10. Distinguish between electric arc welding and resistance welding. (10×4=40 Marks)
PART – II
Each question carries 20 marks.
Module – I
11. a) Derive from first principles, the capacitance per km to neutral of a 3-phase
overhead transmission line with unsymmetrical spacing of conductors.
b) Calculate the chraging current of a 3-ph, 50 Hz, 33 KV, 3 conductor overhead
transmission line, 10 Km long, having conductor dia 20 mm, spaced 2.5 ms, at
the corners of an equilateral triangle.
OR
12. a) Explain the significance of using per unit system in power system analysis.
b) A 3-ph, 220 KV, 50 Hz transmission line, 200 Km long transmits a load of
75 MW at 0.8 p.f. lagging at the receiving end. Resistance of the line/ph/km =
0.8 ohm, susceptance/ph/km = 6 ?? 10–6 mho, Reactance/ph/km = 0.8 ohm.
Determine :
a) the ABCD constants of the line and
b) sending end voltage and current
Module – II
13. a) Describe the various systems of power transmission and compare the conductor
material (volume) for 3-ph, 3 wire a.c. with that of 3 wire d.c. State the assumptions
made.
b) A 33 KV, 3-ph, underground cable, 4 km long uses three single core cables.
Each of the conductors has a diameter of 2.5 cm and the radial thickness of
insulation is 0.5 cm. The relative permitivity of the dielectric is 3.0. Determine (a)
the capacitance of the cable/ph and (b) charging current/ph.
OR
-3- 8075
14. a) Explain briefly about the various conductor materials used for overhead lines.
Give their relative advantages and diadvantages.
b) Find the disruptive critical voltage and visual critical voltage (for local and general
corona) for a 3-ph line having 1 cm dia conductors, spaced in 3 m delta
arrangement. Assume temperature 26°C, pressure 74 cm of mercury, surface
factor 0.85 and irregularity factor for local visual corona 0.72 and general visual
corona 0.82.
Module – III
15. a) What are the causes of low power factor in an electrical system and discuss the
methods for improving the power factor ?
b) A consumer takes a steady load of 300 KW at a lagging p.f. of 0.7 for
3000 hours in a year. The tariff is Rs. 130/KVA of M.D. annually and 4 paise per
KWh. The annual cost of phase advancing plant is Rs. 13.00 per KVAR.
Determine the annual saving, if the p.f. of the load is improved to 0.9.
OR
16. a) What is specific energy consumption ? Explain the factors that affect the specific
energy consumption of a train operating at given scheduled speed.
b) The average distance between stops on a level section of railway is 1.5 Km. The
train weighing 200 tonnes has a scheduled speed of 32 km/hr, the duration of the
stops being 25 sec. The acceleration is 1.9 km/hr/sec and braking retardation is
3.2 km/hr/sec. Train resistance to traction is 40 Nw/tonne. Allowance for rotational
inertia is 10%. Calculate the specific energy output in watt hours per tonne km
for the run. Assume trapezoidal speed-time curve.
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