Electrical Power Transmission MCQs Part 13
Contents
- 1 Sag in overhead transmission lines depends on
- 2 If shunt capacitance decreases in string of suspension insulators, then string efficiency
- 3 In order to improve string efficiency using method of capacitance grading, the maximum capacitance is of disc
- 4 If spacing between conductors is decreased, the inductance of line
- 5 Cross-arms for power transmission lines are generally made of
Sag in overhead transmission lines depends on
Sag in overhead transmission lines depends on:
- Conductor material
- Tension I conductor
- Tower height
- All of these
Correct answer: 4. All of these
If shunt capacitance decreases in string of suspension insulators, then string efficiency
If shunt capacitance decreases in string of suspension insulators, then string efficiency:
- Increases
- Decreases
- Remains unchanged
- None of these
Correct answer: 1. Increases
Explanation:
Mathematical formula for string efficiency: (Voltage across string/(n * V’)) * 100
Where n = No of discs
V’ = Voltage across disc nearest to conductor
If shunt capacitance decreases, then, voltage across discs tend to be more uniform. In essence, V’ decease, hence, string efficiency increases.
In order to improve string efficiency using method of capacitance grading, the maximum capacitance is of disc
In order to improve string efficiency using method of capacitance grading, the maximum capacitance is of disc:
- Nearest to conductor
- Nearest to cross-arm
- In middle of string
- None of these
Correct answer: 1. Nearest to conductor
If spacing between conductors is decreased, the inductance of line
If spacing between conductors is decreased, the inductance of line:
- Increases
- Decreases
- Remains unchanged
- None of these
Correct answer: 2. Decreases
Cross-arms for power transmission lines are generally made of
Cross-arms for power transmission lines are generally made of:
- Aluminum
- Copper
- RCC
- Steel
Correct answer: 4. Steel
Explanation: Cross arms for power transmission lines provide support to the insulators. The cross arms are generally made of steel.
Depending on installation, the function of the steel cross arms is to support distribution transformers, fuses, isolating links, and other line equipment. On typical transmission line they serve to provide support to the insulators.