Electrical Power Transmission MCQs Part 13

Electrical Power Transmission MCQs Part 13

Sag in overhead transmission lines depends on

Sag in overhead transmission lines depends on:

1. Conductor material
2. Tension I conductor
3. Tower height
4. 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:

1. Increases
2. Decreases
3. Remains unchanged
4. 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:

1. Nearest to conductor
2. Nearest to cross-arm
3. In middle of string
4. 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:

1. Increases
2. Decreases
3. Remains unchanged
4. 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:

1. Aluminum
2. Copper
3. RCC
4. 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.