QP: Electrical Power Engineering

GUJARAT TECHNOLOGICAL UNIVERSITY

B.E. Sem-Vth Examination December 2010

Subject code: : 150801

Subject Name: Electrical Power Engineering

Date: 16 /12 /2010 Time: 03.00 pm – 05.30 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) Draw and explain the schematic arrangement of nuclear power plant. Also explain the functions of:

  1. Moderator
  2. Fuel rods
  3. Control rods

 

07
(b) A 1 phase motor connected to 400V,50 Hz supply takes 25A at a p.f. of 0.65lag. Calculate the capacitance required in parallel with motor to raise p.f. to 0.90lag.  07
Q.2 (a) Define tariff and explain in detail:

  1. Two- part tariff
  2. Power factor tariff
  3. Three-part tariff

 Answer Link

07
(b) A power station has following daily load cycle:Time(hrs)  Load(MW)0-6              20

6-10            30

10-12          45

12-16          60

16-20          40

20-24          30

Draw load curve .Also calculate:

  1. Average load
  2. Load factor

 

07
OR(b) Calculate volume of conductor material used in

  1. Overhead system, with 3wire dc system
  2. Underground system, with 3 phase 3wire system

 

07
Q.3 (a) Explain string efficiency and methods of improving it. Answer Link
07
(b) Explain corona with advantages and disadvantages of it. Also define:

  1. Critical disruptive corona voltage.
  2. Visual corona voltage.

 

07
ORQ.3 (a) Explain FACTS devices.  07
(b) Explain different equipments used in substations with its symbols. 07
Q.4 (a) Define underground cables, draw and explain internal construction of it.  07
(b) A transmission line has a span of 100m between level supports. The conductor has cross-section area of 5cm2. The tension is the conductor is 2500 kg. If specific gravity of conductor material is 9.98m /cm3 and wind pressure is 1.2 kg/m. Calculate sag and vertical sag.  07
ORQ.4 (a) A part of transposition cycle of 3phase double circuit line is shown below. Radius of each conductor is 0.9cm.The conductors are made up of solid copper. Find the inductance/phase/km of the line.[image]  07
(b) Explain following in respect to medium transmission line.

  • Nominal T method
  • Nominal π method

 

07
Q.5 (a) Draw and explain following distribution schemes:

  1. Secondary AC distribution system
  2. Radial distribution system
  3. Ring main distribution system

 

07
(b) Explain importance of voltage control and method to achieve it. 07
ORQ.5 (a) Differentiate most economical p.f. and most ideal p.f 02
(b) Explain:

  1. Diversity factor
  2. Plant capacity factor
  3. Load factor

Answer Link

05
(c) A two conductor street mains AB, 500 m in length is fed from both ends at 250 V. Loads 50 A, 60 A,40 A and 30 A are tapped at distance of 100 m, 250 m, 350 m, and 400 m from A respectively. If cross section area of the conductors be 1 cm2 and specific resistance of conductors is 1.7 × 10 -8 Ωm. Determine minimum consumer voltage. 07

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