# Objective Type Question or MCQ of B. Economics of Operation page-4

31. Stringing chart useful for

a) Finding the sag in the conductor.
b) In the design of tower.
c) In the design of insulator string.
d) Finding the distance between the tower.

Ans: (a)

32. For an existing a.c. transmission line the string efficiency is 80. Now of d.c. voltage is supplied for the same set up, the string efficiency will be

a) 80%
b) More than 80%
c) Less than 80%
d) 100%

Ans: (d)

33. Coefficient of reflection for current for an open ended line is

a) 1.0
b) 0.5
c) – 1.0
d) Zero.

Ans: (c)

34. Leakage resistance of a 50 km long cable is 1 MΩ. For a 100 km long cable it will be

a) 1 MΩ
b) 2 MΩ
c) 0.66 MΩ
d) None of the above

Ans: (d)

35. A voltmeter gives 120 oscillations per minute when connected to the rotor. The stator frequency is 50 Hz. The slip of the motor is

a) 2%
b) 4%
c) 5%
d) 2.5%

Ans: (b)

36. Solution of coordination equations takes into account

a) All the system constraints.
b) All the operational constraints.
c) All the system and operation constraints.
d) None of the above.

Ans: (d)

37. Charging reactance of 50 km length of line is 1500 Ω. The charging reactance for 100km length of line will be

a) 1500 Ω
b) 3000 Ω
c) 750 Ω
d) 600 Ω

Ans: (c)

38. In a two plant system, the load is connected at plant no 2. The loss coefficients

a) B11, B12, B22 are nonzero.
b) B11 and B22 are nonzero but B12 is zero.
c) B11 and B12 are nonzero but B22 is zero.
d) B11 is nonzero but B12 and B22 are zero.

Ans: (d)

39. Ferranti effect on long overhead lines is experienced when it is

b) On full load at unity p.f.
c) On full load at 0.8 p.f. lag.
d) In all these case.

Ans: (a)

40. In-rush current of a transformer at no load is maximum if the supply voltage is switched on

a) At zero voltage value.
b) At peak voltage value.
c) At V/2 value.
d) At √3/2 value.

Ans: (a)