Electrical Engineering: Power system MCQ

16. Question

The magnitude of three-phase fault currents at buses A and B of a power system are 10 pu and 8 pu, respectively. Neglect all resistances in the system and consider the pre-fault system to be unloaded. The pre-fault voltage at all buses in the system is 1.0 pu. The voltage magnitude at bus B during a three-phase fault at bus A is 0.8 pu. The voltage magnitude at bus A during a three-phase fault at bus B, in pu, is ________.




Answer
17. Question

In a 100 bus power system, there are 10 generators. In a particular iteration of Newton Raphson load flow technique (in polar coordinates), two of the PV buses are converted to PQ type. In this iteration,




Answer
18. Question

A source is supplying a load through a 2-phase, 3-wire transmission system as shown in figure below. The instantaneous voltage and current in phase -a are van = 220sin(100πt) V and ia = 10sin(100πt) A respectively. Similarly for phase-b, the instantaneous voltage and current are Vbn = 220cos(100πt) V and ib = 10cos(100πt) A, respectively. 

The total instantaneous power flowing from the source to the load is




Answer
19. Question

The per-unit power output of a salient-pole generator which is connected to an infinite bus, is given by the expression, P = 1.4 sin δ + 0.15 sin 2δ, where δ is the load angle. Newton- Raphson method is used to calculate the value of δ for P = ⁡0.8 pu. If the initial guess is 30°, then its value (in degree) at the end of the first iteration is




Answer
20. Question

Consider an overhead transmission line with 3-phase, 50 Hz balanced system with conductors located at the vertices of an equilateral triangle of length D ab = D bc = D ca =1 m as shown in figure below. The resistances of the conductors are neglected. The geometric mean radius (GMR) of each conductor is 0.01 m. Neglect the effect of ground, the magnitude of positive sequence reactance in Ω/km (rounded off to three decimal places) is ___________




Answer