1. Questions Q1) Briefly discuss the various types of conductor material used for
overhead transmission lines
Q2) A solid cylindrical aluminum conductor 25 km long has an area of
336,400 circular mils. Obtain the conductor resistance at (a) 20oC and (b)
50oC. The resistivity of aluminum at 20oC is 2.8 * 108 Ω/m.
(Note; 1inch = 1000mils)
𝐴 = 𝑑 !
1 𝑖𝑛𝑐ℎ = 2.54 𝑐𝑚
Dr. Mohammed Alqarni
Q3) A transmission-line cable consists of 12 identical strands of
aluminum, each 3 mm in diameter. The resistivity of aluminum strand at
20oC is 2.8 * 108 Ω/m. Find the 20oC AC resistance per Km of the cable.
Q4) A single phase transmission line 35 km long consists of two solid
round conductors, each having a diameter of 0.9cm. The conductor
spacing is 2.5 m and the frequency is 60Hz.
a) What is the value of inductance per conductor?
b) What is the value of series inductive reactance per line?
c) What is the shunt capacitance per kilometer of this line?
d) What is the total shunt admittance and capacitance of this line?
𝑙=
𝜇 1
𝐷
+ 𝑙𝑛
×1000
2𝜋 4
𝑟
4𝜋×10!! 1
2.5
=
+ 𝑙𝑛
×1000 = 1.314𝑚𝐻/𝑘𝑚
2𝜋
4
. 45×10!!
𝐿!"!#$ = 𝑙×35 = 1.314×35 = 46 𝑚𝐻/𝑘𝑚
Dr. Mohammed Alqarni
B)
𝑙!"#$ = 2 ×𝐿!"!#$ = 2×46 = 92 𝑚𝐻/𝑘𝑚
𝑋! = 𝑗2𝜋𝑓𝑙×35 = 2×𝜋×60×92×10!! ×35 = 𝑗1213.9Ω
c)
𝑐=
𝜋𝜀
𝜋×8.854×10!!"
×1000 =
×1000 = 4×10!! 𝐹/𝑘𝑚
𝐷
2.5
𝑙𝑛 𝑟
𝑙𝑛
. 45×10!!
d) The shunt admittance per line 𝑌! = 𝑗2𝜋𝑓𝑐×35 = 2×𝜋×60×4×10!! ×35 = 𝑗58×10!! 𝑆 𝑋! =
1
1
=
= −𝑗17.219 𝑘Ω 𝑌! 𝑗58×10−6
Dr. Mohammed Alqarni