PYQs Based test 13: Power Systems

A load is supplied by a 230 V, 50 Hz source. The active power P and the reactive power Q consumed by the load are such that 1 kW ≤ P ≤ 2 kW and 1 kVAR ≤ Q ≤ 2 kVAR. A capacitor connected across the load for power factor correction generates 1 kVAR reactive power. The worst case power factor after power factor connection is

A composite conductor consists of three conductors of radius R each. The conductors are arranged as shown below. The geometric mean radius (GMR) (in cm) of the composite conductor is kR. The value of k is_______.

A 3 – bus power system network consists of 3 transmission lines. The bus admittance matrix of the uncompensated system is

≤ft[ {*20c - j6&j3&j4\\ j3& - j7&j5\\ j4&j5& - j8 } ]Pu

If the shunt capacitance of all transmission lines is 50% compensated, the imaginary part of the 3${}^{rd}$ row 3${}^{rd}$ column element (in pu) of the bus admittance matrix after compensation is

The figure shows the single line diagram of a single machine infinite bus system.



The inertia constant of the synchronous generator H = 5 MW –s / MVA. Frequency is 50 Hz. Mechanical power is 1 pu. The system is operating at the stable equilibrium point with rotor angle δ equal to 30°. A three phase short circuit fault occurs at a certain location on one of the circuits of the double circuit transmission line. During fault, electrical power in pu is P${}_{max}$

sin δ. If the values of δ and dδ / dt at the instant of fault clearing are 45° and 3.762 radian/s respectively, then P${}_{max}$ (in pu) is___________.

A three phase, 100 MVA, 25kV generator has solidly grounded neutral. The positive, negative, and the zero sequence reactances of the generator are 0.2 pu, 0.2 pu, and 0.05 pu, respectively, at the machine base quantities. If a bolted single phase to ground fault occurs at the terminal of the unloaded generator, the fault current in amperes immediately after the fault is________.