This set of Power Systems Interview Questions and Answers for freshers focuses on “Inductance of Composite Conductor Lines – 3”.

1. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. The voltage regulation will be _______

a) 16.8 %

b) 18.8%

c) 21.75%

d) 12.8%

View Answer

Explanation: VR = (11.68-10)*100/10 = 16.8 %.

2. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. Identify the transmission line and the voltage regulation.

a) STL, 11.68%

b) MTL, 11.68

c) STL, 21.5%

d) MTL, 14.2%

View Answer

Explanation: It is a short transmission line.

Current, I = 5000/(10*0.8)=625 A

V

_{s}= |V

_{r}|+|I|*(RcosФ

_{r}+ XsinФ

_{r})

= 10000+625(0.39*0.8+3.96*0.6)

= 11.68kV

VR = (11.68-10)*100/10 = 16.8 %.

3. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. The half the voltage regulation will be _____________

a) 8.4 %

b) 16.8 %

c) 14.2%

d) 10.5%

View Answer

Explanation: VR = (11.68-10)*100/10 = 16.8 %

Half the VR = 16.8/2 % = 8.4%.

4. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. The new sending end voltage at the half the voltage regulation is _____________

a) 10.84 kV

b) 11.84 kV

c) 8.84 kV

d) 16.2 kV

View Answer

5. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. If the voltage regulation is reduced to 50%, then the power factor at this operation mode will be _________________

a) 0.95

b) 0.92

c) 0.74

d) 0.90

View Answer

Explanation: VR = (11.68-10)*100/10

VR = 16.8 %

Half the VR = 16.8/2 %

Half the VR = 8.4%

(10.84-10)*1000 = |I|*( RcosФ

_{r}+ XsinФ

_{r}) …(1)

I = 5000/(cosФ

_{r}*10) …(2)

Solving above eqaution

Ф

_{r}= 18.04°

Cos Ф

_{r}= 0.9508, lagging.

6. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. If the voltage regulation is reduced to 50%, then the power factor angle at this operation mode will be _____________

a) 18.04°

b) 8.04°

c) 21.06°

d) 12°

View Answer

Explanation: VR = (11.68-10)*100/10

VR = 16.8 %

Half the VR = 16.8/2 %

Half the VR = 8.4%

(10.84-10)*1000 = |I|*(RcosФ

_{r}+ XsinФ

_{r}) …(1)

I = 5000/(cosФ

_{r}*10) …(2)

Solving above equation

Ф

_{r}= 18.04°.

7. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. If the voltage regulation is reduced to 50%, then the power factor at this operation mode will be ____________

a) 0.95, lagging

b) 0.92, leading

c) 0.95, lagging

d) 0.90, leading

View Answer

Explanation: VR = (11.68-10)*100/10

VR = 16.8 %

Half the VR = 16.8/2 %

Half the VR = 8.4%

(10.84-10)*1000 = |I|*(RcosФ

_{r}+ XsinФ

_{r}) …(1)

I = 5000/(cosФ

_{r}*10) …(2)

Solving above equation

Ф

_{r}= 18.04°

Cos Ф

_{r}= 0.9508, lagging.

8. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. If the voltage regulation is reduced to 50%, then the power factor angle at this operation mode will be ________

a) 18.04°, lagging

b) 18.04°, leading

c) 21.06°, leading

d) 21.06°, lagging

View Answer

Explanation: VR = (11.68-10)*100/10

VR = 16.8 %

Half the VR = 16.8/2 %

Half the VR = 8.4%

(10.84-10)*1000 = |I|*(RcosФ

_{r}+ XsinФ

_{r}) …(1)

I = 5000/(cosФ

_{r}*10) …(2)

Solving above equation

Ф

_{r}= 18.04°, lagging.

9. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is 11.68 kV. If the voltage regulation is reduced to 50%, then the receiving end current at this operation mode will be _____________

a) 526 A

b) 549 A

c) 521 A

d) 580 A

View Answer

Explanation: VR = (11.68-10)*100/10

VR = 16.8 %

Half the VR = 16.8/2 %

Half the VR = 8.4%

(10.84-10)*1000 = |I|*(RcosФ

_{r}+ XsinФ

_{r}) …(1)

I = 5000/(cosФ

_{r}*10) …(2)

Solving above equation

Ф

_{r}= 18.04°, lagging

I = 526 A.

10. Suppose the transmission line is loaded with its surge impedance, the receiving-end voltage is greater than sending end voltage.

a) True

b) False

View Answer

Explanation: It will be equal.

**Sanfoundry Global Education & Learning Series – Power Systems.**

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