Electrical Engineering MCQs on Power Transmission Part 21
Contents
- 1 Sag is provided in overhead transmission lines in order to ensure
- 2 A 33 kV overhead line has 3 units in string of insulation, the voltage across string is
- 3 A round conductor has diameter of 1 cm. Its geometrical mean radius (G.M.R) is
- 4 The line constants of a transmission line are
- 5 132 kV transmission line is more likely to use insulators of which type
Sag is provided in overhead transmission lines in order to ensure
Sag is provided in overhead transmission lines in order to ensure
- Maintenance can be done
- Safe tension is not exceeded
- Economical use of material
- None of these
Correct answer: 2. Safe tension is not exceeded
Explanation:
Mathematical formula for sag is: S = (wl²)/8T
Where: S = Sag; T = Tension; w = Weight of conductor; l = span length
Since sag is inversely proportional to the tension in conductor, its basic application in overhead transmission lines is to reduce the tension.
Also see: Sag Formula and Calculations in Transmission Lines
A 33 kV overhead line has 3 units in string of insulation, the voltage across string is
A 33 kV overhead line has 3 units in string of insulation, the voltage across string is:
- 11 kV
- 19.05 kV
- 22 kV
- 33 kV
Correct answer: 2. 19.05 kV
Formula:
Voltage across string = Phase voltage = 33/√3 = 19.05 kV
See also: Top 5 Types of Insulators Used on Power Transmission and Distribution Lines
A round conductor has diameter of 1 cm. Its geometrical mean radius (G.M.R) is
A round conductor has diameter of 1 cm. Its geometrical mean radius (G.M.R) is:
- 0.433 cm
- 0.7788 cm
- 0.9545 cm
- 1 cm
Correct answer: 2. 0.7788 cm
The line constants of a transmission line are
The line constants of a transmission line are:
- Uniformly distributed
- Non-uniformly distributed
- Lumped
- None of these
Correct answer: 1. Uniformly distributed
132 kV transmission line is more likely to use insulators of which type
132 kV transmission line is more likely to use insulators of which type:
- Disc type
- Shackle type
- Pin type
- None of these
Correct answer: 1. Disc type
Explanation: Suspension type insulators or disc type insulators consist of a number of porcelain discs that are connected in series by metal links in the form of a string.
One end of the insulator string is secured to the cross-arm of the tower while on the other end conductor is suspended. Each disc in suspension insulator is designed for low voltage (around 11 kV).
For voltage levels above 33 suspension type or disc type insulators are preferred.