T&D Quiz Unit 1

The surge impedance of 50 miles long underground cable is 50 ohms. For a 25 mile length, it will be

• 25 ohms

• 50 ohms

• 100 ohms

• None of the above

The self GMD method is used to evaluate

• Inductance

• Capacitance

• Inductance and capacitance both

• None of the above

The inductance of a single phase 2 wire transmission line per km gets doubled when

• the distance between the wires is doubled

• distance between the wires is increased four fold

• distance between the wires is increased as square of the original distance

• radius of the wire is doubled

Transmission lines are transposed to

• reduce copper loss

• reduce skin effect

• prevent interference with neighbouring telephone lines

• prevent short circuit between any two lines

A single phase transmission line of impedance j0.8 ohm supplies a resistive load of 500A at 300V. The sending end power factor is

• unity

• 0.8 lag

• 0.8 lead

• 0.6 lag

Bundled conductors in transmission line provide

• reduced capacitance

• increased capacitance

• increased inductance

• increased voltage gradient

When bundle conductors are used in place of single conductors, the effective inductance and capacitance will respectively

• increase and decrease

• decrease and increase

• decrease and remains unaffected

• remains unaffected and increase

The inductance of a three phase transmission line is 1.2mH/ph/km.If the spacing of conductors and the radius of the conductor are doubled, then the inductance of the line will be

• 4.8mH/ph/km

• 1.2 mH/ph/km

• (Logn2)*1.2mH/ph/km

• (Logn4)*1.2mH/ph/km

Which one of the following statements is not true for the use of bundled conductors in transmission lines

• Control of voltage gradient

• Reduction in corona loss

• Reduction in inductance

• Increase in interference with communication lines

A three phase transmission line has conductors arranged in horizontal spacing with 'd' as the distance between the conductors. If these conductors are rearranged to form an equilateral triangle with sides equal 'd', then the

• Capacitance and Inductance will increase

• Capacitance will increase and inductance will decrease

• Capacitance and inductance will remain the same

• Capacitance will decrease and inductance will increase