Anna University Chennai 2005 B.E Electrical and Electronics Engineering Fifth Semester EE335 – Transmission and Distribution - Question Paper

B.E. Electrical and Electronics Engineering

Time : three Hours Max Marks : 100
PART – A
ans All ques. (10 x two = 20 marks)
1. Mention the advantages of using ACSR conductor as overhead line.
2. elaborate stranded conductors? Why is it used?
3. explain skin and proximity effects?
4. discuss changing current of a transmission line.
5. Draw equivalent circuit and phasor diagram for short transmission line.
6. What is the nature of reactive power compensation for peak load and off peak load
conditions?
7. provide cause for using a greater number of insulator discus for transmission lines
placed in heavily polluted areas.
8. Compare the power transmission using overhead line and underground cable.
9. explain different factors affecting sag.
10. Write briefly about conservation of energy.
PART – B (5 x 16 = 80 Marks)
11.i) discuss the various kinds of HVDC links and state the advantages of HVDC
transmission over AC transmission.
ii) discuss why the transmission lines are three phase 3-wire circuits while distribution lines
are three phase 4-wire circuits.
12.a) Derive an expression for inductance
i) of a single-phase overhead line.
ii) A conductor is composed of 7 identical copper strands every having
a radius r. obtain the self-GMD of the conductor.
OR
12.b)i) Derive an expression for the capacitance ranging from conductors of a single-phase
overhead line.
ii) obtain the capacitance ranging from the conductors of a single-phase 10 km long line. The
diameter of every conductor is 1.213cm. The spacing ranging from conductors is 1.25m.
Also obtain the capacitance of every conductor neutral.
13.a)i) Show that the real power transferred is dependent on the power angle and the reactive
power transferred is dependent on the voltage drop in the line.
ii) The constants of a 3-phase lines are A=0.9 2? and B=140 70? O / phase. The lines
delivers 60 MVA at 132 kV and 0.8 pf lagging. Draw circle diagrams and obtain.
i. sending end voltage and power angle.
ii. The maximum power, which the line can deliver with the above values
of sending end and receiving end voltages.
iii. Sending end power and power factor.
iv. Line losses.
OR
13.b)i) What is an equivalent ? circuit of long line? Derive expression for parameters of this
circuit in terms of line parameters.
ii) A 50Hz transmission line 300 km long total series impedance of 40+j25 O and total
shunt admittance of 10-3 mho. The 220 Kv with 0.8 lagging power factor. obtain the
sending end voltage, current, power and power factor using nominal ? method.
14.a)i) elaborate various methods to improve string efficiency of an insulator?
ii) In a 3-unit insulator, the joint to tower capacitance is 20% of the capacitance of every
unit. By how much should the capacitance of the least unit be increased to get a
string efficiency of 90%. The remaining 2 units are left unchanged.
OR
14.b)i) Derive the expression for insulator resistance, capacitance and electric stress in a
single core cable. Where is the stress maximum and minimum?
ii) A single core 66kv cable working on 3-phase system has a conductor diameter of 2cm
and sheath of inside diameter 5.3cm. If 2 inner sheaths are introduced in a such a
way that the stress varies ranging from the identical maximum and minimum in the three
layers find:
1. position of inner sheaths
2. voltage on the linear sheaths
3. maximum and minimum stress
15.a)i) Derive the expressions for sag and conductor length under bad weather conditions.
presume shape of overhead line is a parabola.
ii) An overhead line has a span of 300m. The conductor diameter is 1.953cm and the
conductor weight is 0.844kg/m. compute the vertical sag when a wind pressure is
736 N/sq.m of projected area acts on conductor. The breaking strength of conductor is
77990N and the conductor should not exceed half the breaking strength.
OR
15.b)i) discuss various kinds Traiff.
ii) Why a consumer having low power factor is changed at high rates.

Earning:   Approval pending.