a) Xohms = (X(%) ×100 (kV)2)/kVA b) Xohms = (X(%) ×1000 (kV)2)/kVA c) Xohms = (X(%)×(KV)2)/(1000 kVA) d) Xohms = (X(%)×10(kV)2)/kVA Ans: (d)
a) Sub-transient reactance b) Transient reactance c) Synchronous reactance d) Either (a) or (c) Ans: (c)
a) Zero as time goes to infinity b) Maximum when time goes to infinity c) Infinity when time goes to infinity d) Small as time goes to infinity but not zero e) None of the above Ans: (a)
a) Because the high resistance will not help to limit the short circuit current b) To avoid the energy waste c) Because the high resistance will raise the temperature and insulation of reactor will be spoiled d) To improve power factor Ans: (b)
a) Which rotates the vector, it operates upon, through an angle 90° in the clockwise direction b) Which rotates the vector, it operates upon, through an angle 120°, in the counter-clockwise direction c) Which rotates the vector, it operates upon, through an angle120°, in the clockwise direction d) Which rotates the vector, it operates upon, through an angle 240°, in the clockwise direction Ans: (b)
a) a = 0.5 – j 0.866 b) a = 0.5 + j 0.866 c) a4 = - a d) a2 = - (1 + a) Ans: (d)
a) In the phase with the are current b) Lagging the arc current by 90° c) Leading the arc current by 90° d) Leading the are current by 180° Ans: (a)
a) true b) false Ans: (a)
a) Low melting point and low specific resistance b) Low melting point and high specific resistance c) High melting point and low specific resistance d) Low melting point with any specific resistance Ans: (b)
a) Alternators against all internal faults b) Oil immersed transformers against all internal faults c) Synchronous motors against all internal faults d) Transmission lines against all short circuit faults Ans: (b)