### 21. If L, C and Y are the inductance, capacitance and shunt admittance of a line per unit length, then for length *l*.

(a) the shunt admittance is Y.*l*.

(b) the inductance is L÷*l*.

(c) the capacitance is C÷*l*.

(d) the shunt admittance is Y÷*l*.

**Answer: (a) the shunt admittance is Y.**

*l*.### 22. Transmission efficiency of a transmission line increases with the

(a) decrease in power factor and voltage.

(b) increase in power factor and voltage.

(c) increase in power factor but decrease in voltage.

(d) increase in voltage but decrease in power factor.

**Answer: (b) increase in power factor and voltage.**

### 23. Under no-load conditions, the current in a transmission line is because of

(a) capacitance effect.

(b) corona effect.

(c) proximity effect.

(d) back flow from earth.

**Answer: (a) capacitance effect.**

### 24. Which of the following statements are correct ?

(a) Flow of unduly heavy current is Ferranti effect.

(b) Ferranti effect occurs under unloaded condition of line.

(c) The rise in receiving-end voltage is Ferranti effect.

(d) Both (b) and (c) combined is Ferranti effect.

**Answer: (d) Both (b) and (c) combined is Ferranti effect.**

### 25. In a long transmission line under no-load condition

(a) the receiving-end voltage is less than the sending and voltage.

(b) the sending-end voltage is less than the receiving-end voltage.

(c) the sending-end voltage is equal to the receiving-end voltage.

(d) none of these.

**Answer: (b) the sending-end voltage is less than the receiving-end voltage.**

### 26. When is the Ferranti effect on long overhead lines experienced?

(a) The line is lightly loaded.

(b) The line is heavily loaded.

(c) The line is fully loaded.

(d) The power factor is unity.

**Answer: (a) The line is lightly loaded.**

### 27. Ferranti effect happens in transmission line when the line is

(a) short and loaded.

(b) long and loaded.

(c) long and unloaded.

(d) none of these.

**Answer: (c) long and unloaded.**

### 28. The ABCD constants of a 3 phase transposed transmission line with linear and passive elements

(a) are always equal.

(b) never equal.

(c) A and D are equal.

(d) B and C are equal.

**Answer: (c) A and D are equal.**

### 29. The values of A, B, C and D constants for a short transmission line are respectively

(a) Z, 0, 1 and 1.

(b) 0, 1, 1 and Z.

(c) 1, Z, 0 and 1.

(d) 1, 1, Z and O.

**Answer: (c) 1, Z, 0 and 1.**

### 30. The angle of A, constant of the transmission line normally lies between

(a) 90° – 70°

(b) 70° – 40°

(c) 40° – 40°

(d) 10°- 0°

**Answer: (d) 10°- 0°**

### 31. For a transmission line with resistance R, reactance X and negligible capacitance, the generalized constant A is

(a) 0

(b) 1

(c) R + j X

(d) R + X

**Answer: (b) 1**

### 32. The value of the ‘A’ parameter of a transmission line

(a) increases with the increase in length of the line.

(b) decreases with the increase in line length.

(c) is independent of line length.

**Answer: (a) increases with the increase in length of the line.**

### 33. For a medium length transmission line, A is

(a) equal to B.

(b) equal to C.

(c) equal to D.

(d) not equal to any of the above.

**Answer: (c) equal to D.**

### 34. The generalized constant A for a medium line has magnitude

(a) close to but less than 1.

(b) close to but greater than 1.

(c) nearly equal to the series impedance of the line.

**Answer: (a) close to but less than 1.**

### 35. For transmission line which one of the following relations is true?

(a) AD – BC = 1

(b) -AD – BC = 1

(c) AD – BC = -1

(d) AD – BC = 0

Answer: (a) AD – BC = 1

### 36. Which one of the following equations is correct?

(a) -AB + CD = -1

(b) AD + CD = 1

(c) AB – CD = -1

(d) -AD + BC = -1 where A, B, C and D are generalized circuit constants.

**Answer: (d) -AD + BC = -1**

### 37. When the load on a transmission line is equal to the surge impedance loading

(a) the receiving-end voltage is less than the sending-end voltage.

(b) the sending-end voltage is less than the receiving-end voltage.

(c) the receiving-end voltage is equal to the sending-end voltage.

(d) none of these.

**Answer: (c) the receiving-end voltage is equal to the sending-end voltage.**

### 38. The receiving-end voltage of a transmission line will be greater than the sending-end voltage if the load is

(a) greater than SIL (surge impedance loading).

(b) less than SIL.

(c) equal to SIL.

**Answer: (b) less than SIL.**

### 39. The SIL of a single circuit 220 kV line is around

(a) 120 MW

(b) 90 MW

(c) 220 MW

(d) 400 MW

**Answer: (a) 120 MW**

### 40. What is the surge impedance loading of a lossless 400 kV, 3-phase, 50 Hz overhead line of average of surge impedance of 400 ohms?

(a) 400 MW

(b) 400√3 MW

(c) 400 ÷ √3 MW

(d) 400 kW

**Answer: (a) 400 MW**

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