POWER SYSTEM MCQS SET 10

POWER SYSTEM MCQS SET 10

1․ Length of the cable is doubled, its capacitance C will be
a. one-fourth.    b.  one-half.       c. doubled.      d. unchanged.
Explain:
The length of the cable and the capacitance of the cable are directly proportional to each other. Hence, if the length gets doubled, then the capacitance also can be doubled.

2․ Tarapur nuclear power plant has which type of reactor?
a. Pressurized water reactors.     b.   Boiling water type.
c.  CANDU type reactors.              d.  None of these.
Explain:
The Tarapur Atomic Power Station (T.A.P.S.) is located in Tarapur, Maharashtra, India has initially built with two boiling water reactor with the capacity of 210 MW on 1969. But, now this plant has two extra pressurized heavy water reactor with the capacity of 540 MW on 2006.

03․ Which of the following rotor is used in thermal power plants?
a. cylindrical rotor    b.  salient pole rotor     c.  either of these
d.  squirrel cage rotor
Explain:
Cylindrical rotor is also called as round rotor or smooth rotor, there is no projection, there a closed portion contain field winding which is distributed and unslotted portion also acts as poles . It has large axial length and small diameter, resulting high peripheral speed. As the air gap is uniform throughout the machine it is more suitable for high speed operation, employed in all thermal, nuclear power plants containing turbo alternators with two or maximum 4 poles only.

04․ Four identical alternators each are rated for 20 MVA, 11 KV having a subtransient reactance of 16% are working in parallel. The short circuit level at the busbar is
a. 500 MVA      b. 400 MVA       c. 125 MVA         d. 100 MVA
ANSWER: a

05․ India’s largest thermal power station is located at
a. Kota.          b. Sarni.        c. Chandrapur.          d. Neyveli.
Explain:
The plant was officially inaugurated by the then Prime Minister Indira Gandhi on 8th October, 1984. With the total capacity of 3340 MW and this plant is largest thermal power plant in the India. It accounts to more than 25% of total Maharashtra needs.

06․ Oxide film arrestor has which of the following properties?
a. Does not require daily charging.
b. Installed at points of transmission line where daily visit is difficult.
c. It is expensive.                 d. Both A and B.
Explain:
The both properties are essential properties of an oxide film lightning arrestor.

07․ What is the total installed power capacity (MW) in West Bengal as published by ministry of power in 2011?
a. 6114.05.        b. 10000.32.    c. 8113.27.                d. 15515.22.
ANSWER: c

08․ What should be the minimum depth (in metre) of cable trench to dug for laying of 1.1 kV?
a. 0.75         b. 0.90      c. 1.05            d. 1.20
ANSWER: a
 

09․ NTPC (National Thermal Power Cooperation) has its only thermal power generating unit in West Bengal at
a. Durgapur.            b. Bakreshwar.          c. Farakka.          d. Katwa
Explain:
Farakka super thermal power plant is under the thermal power generating unit of NTPC in West Bengal. The actual place is P.O. Nabarun - 742 236, Dist. Murshidabad, West Bengal.

10․ If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400 : 5, then plug setting multiplier will be
a. 10            b. 15           c. 25              d. 50
Explain:
The current transformer ratio is 400 / 5. So, the CT can be provided a rated current of 5 Amps to the relay coil. Thereby the rated relay current is 5 Amps. If the relay setting is 50%, then the relay can be operated for 5 × ( 50 / 100 ) = 2.5 Amps. This is the pick-up current of that relay. We know that the fault current is 2000 Amps. Hence, the fault current in the secondary of the CT is 5 × ( 2000 / 400) = 25 Amps. Hence, the plug setting multiplier = 25 / 2.5 = 10. That means the fault current in the secondary of the CT is ten times greater than the operating current of relay coil.