Electrical Power Transmission MCQs Part 18

Contents

- 1 A string of insulators in a 33 kV overhead transmission has 3 units. Voltage across string is
- 2 Wind pressure is directly proportional to
- 3 If span length is doubled without changing other factors, the sag of line will become
- 4 With an increase in length of transmission lines, the inductive reactance XL
- 5 Bundled conductors are used in order to

## A string of insulators in a 33 kV overhead transmission has 3 units. Voltage across string is

A string of insulators in a 33 kV overhead transmission has 3 units. Voltage across string is:

- 33 kV
- 66 kV
- 33/√3 kV
- 27.92 kV

Correct answer: 3. 33/√3 kV

## Wind pressure is directly proportional to

Wind pressure is directly proportional to:

- Square of speed of wind
- Speed of wind
- Square root of speed of wind
- None of these

Correct answer: 1. Square of speed of wind

## If span length is doubled without changing other factors, the sag of line will become

If span length is doubled without changing other factors, the sag of line will become:

- 1.5 times
- 2 times
- 4 times
- 8 times

Correct answer: 3. 4 times

Explanation:

Mathematical formula for sag is: S = (wl²)/8T

Considering other factors as constant, assume S = S1: Sag ∝ l²

Now when doubled assuming new sage S = S2: Sag ∝ (2l)²

Now S2/S1 = (2l)²/ l² or S2 = 4 S1

Hence Option 3: 4 times is correct.

## With an increase in length of transmission lines, the inductive reactance X_{L}

With an increase in length of transmission lines, the inductive reactance X_{L}:

- Increases
- Decreases
- Remains unchanged
- None of these

Correct answer: 1. Increases

Explanation: With an increases in length of line, the inductance L increases. Formula for inductive reactance is: X_{L} =2π fL

So, with increase in inductance, the inductive reactance will accordingly increase.

## Bundled conductors are used in order to

Bundled conductors are used in order to

- Reduce corona loss and line inductance
- Increase corona loss and reduce line inductance
- Increase line inductance as well as capacitance
- Reduce line inductance as well as capacitance

Correct answer: 1. Reduce corona loss and line inductance

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Electrical Power Transmission MCQs