# Power System

Power System
Question:-
Option (A)
400 kV
Option (B)
500 kV
Option (C)
320 kV
Option (D)
417 kV
Correct Option:
B
Question Solution:
At no-load Vs = AVr as Ir =0
\ Vr = (400/0.8Ð1°) = 500kVÐ-1°
Question:-
Option (A)
0.8 ohm
Option (B)
0.0032 ohm
Option (C)
0.03125 ohm
Option (D)
32.0 ohm
Correct Option:
D
Question Solution:
Z1(actual) = Zpu.Zbase = 0.05 x ((400 x 400)/250) = 32 ohm
Question:-
Option (A)
tan-1(X/R)
Option (B)
tan(R/X)
Option (C)
tan-1(X/Z)
Option (D)
tan-1(R/Z)
Correct Option:
B
Question Solution:
Percent regulation
= (|I|R cosÆR -|I|X sin ÆR)/(|VR|) x 100
For zero voltage regulation
(|I|R cos ÆR -|I|XsinÆR)=0
Þ tan ÆR = (R/X)
Þ ÆR = tan-1 (R/X)
Question:-
Option (A)
Greater than that as motor
Option (B)
Equal to that as motor
Option (C)
Less than that as motor
Option (D)
Greater or less then that as motor depending on the type of the machine
Correct Option:
A
Question Solution:
Pumped storage plant acts as a conventional hydro plant during the peak load period. The turbines are driven by water from the upper reservoir in the usual manner. During the light load period, water in the lower reservoir is pumped back into the upper one so as to be ready for use in the next cycle of the peak load period. The generators in this period change to synchronous motor action and drive the turbines which now work as pumps. The electric power is supplied to the sets from the general power network or adjoining thermal plant. The overall efficiency of the sets is normally as high as 60-70% which suggests that the efficiency of the generator working at the same electrical power level is greater than that of the motor
Question:-
Option (A)
zero
Option (B)
10 MW
Option (C)
30 MW
Option (D)
50 MW
Correct Option:
B
Question Solution:
Capacity factor or plant factor
(70T/max. plant rating x T)
\ plant capacity or maximum plant rating
= (70/0.7) = 100MW
\ Reserve capacity