PYQs Based test 11: Power Systems

A lossless transmission line with 0.2 pu reactance per phase uniformly distributed along the length of the line, connecting a generator bus to a load bus, is protected up to 80 % of its length by a distance relay placed at the generator bus. The generator terminal voltage is 1 pu. There is no generation at the load bus. The threshold pu current for operation of the distance relay for a solid three phase-to-ground fault on the transmission line is closest to:

A 1000 × 1000 bus admittance matrix for an electric power system has 8000 non-zero elements. The minimum number of branches (transmission lines and transformers) in this system are _____ (up to 2 decimal places).

Two generators have cost functions F₁ and F₂. Their incremental-cost characteristics are

$\frac{d{F}_1}{d{P}_1}=40+0.2P_1$

$\frac{d{F}_2}{d{P}_2}=32+0.4P_2$

They need to deliver a combined load of 260 MW. Ignoring network losses, for economic operation, the generations P₁ and P₂ (in MW) are

The nominal-π circuit of a transmission line is shown in the figure.

Impedance Z = 100∠80° Ω and reactance X = 3300 Ω. The magnitude of the characteristic impedance of the transmission line, in Ω, is ________. (Give the answer up to one decimal place.)

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. Neglecting the effect of ground, the magnitude of positive sequence reactance in Ω/km (rounded off to three decimal places) is _________