Distribution System Engineering Course

Topic 2 – Overhead Transmission Lines

ConEdison – June 2014

Name ______

Final Quiz

1. What conductor is more appropriate to operate at very high temperatures? (5 points)

a)  AAC

b)  ACSR

c)  ACSS

2. Comparison between 636kcmil ACSR and 636kcmil ACSR/TW indicates that: (5 points)

a)  636kcmil ACSR/TW is more conductive

b)  They are equally conductive

c) 636kcmil ACSR is less affected by wind loads

3. For ACSR conductors of same aluminum cross-sectional area, which stranding ratio would typically tolerate the highest tension levels? (5 points)

a)  18/1

b)  26/7

c)  30/19

4. By using a typical current density of 2.5 A/mm2, choose the more appropriate conductor for a 115 kV transmission line that will carry 140 MVA and check the right answer below. (5 points)

a)  Hawk

b)  Dove

c)  Grosbeak

5. Short-term emergency thermal ratings are typically: (10 points)

a)  higher than normal thermal ratings

b)  equal to normal thermal ratings

c)  lower than normal thermal ratings

6. An overhead line will typically be able to maximize its thermal rating under the following conditions: (10 points)

a) At noon, with high air temperature, and with low wind speed

b) At night, with low air temperature, and with high wind speed

c) both of the answers are correct

7. What type of shield wire is typically more appropriate for overhead lines located near coastal areas? (10 points)

a) HS

b) EHS

c) Alumoweld

8. What shield wire would be more appropriate to carry an 18 kA short-circuit current for a fault clearing time of 0.25 seconds? Assume the typical parameters shown on slide 4-7. (10 points)

a) EHS 5/8” (A = 0.96 cm2)

b) Alumoweld 7#6AWG (AAL = 0.931 cm2)

c) ACSR Dotterel (AAL = 0.896 cm2)

9. In a typical overhead transmission line, which kind of tower has capability to withstand the highest longitudinal forces? (10 points)

a) suspension towers

b) strain towers

c) they are equally strong

10. Transmission line phase conductors are transposed with the purpose of: (10 points)

a)  reducing the voltage unbalance produced by the transmission line

b)  reducing the harmonics produced by the transmission line

c)  reducing the power losses on the transmission line conductors

11. Guyed lattice towers have the following advantage with respect to self-supporting lattice towers: (10 points)

a)  they are more stable during storms

b)  they are less expensive because of their smaller weight

c)  the location of their foundations typically require a narrower right-of-way

12. Decreasing the tension applied to a transmission line conductor will contribute to: (10 points)

a)  increase the conductor vibration problems

b)  reduce the conductor vibration problems

c)  increase the conductor sag