PYQs Based test 12: Power Systems

A 3 – Phase transformer rated for 33 kV/ 11kV is connected in delta/star as shown in figure. The current transformers (CTs) on low land high voltage sides have a ratio of 500/5. Find the current $i_1$ and $i_2$, of the fault current is 300 A as shown in figure

In an unbalanced three phase system, phase current Iₐ = 1∠(-90°) pu, negative sequence current I${}_{b2}$ = 4 ∠(-150°) pu, zero sequence current I${}_{C0}$ = 3∠ 90° pu. The magnitude of phase current I${}_b$ in pu is

The fuel cost functions of two power plants are

Plant $P1:C_1=0.05P{g}_1^2+AP{g}_1+B$

Plant $P_2:C_2=0.10P{g}_2^2+3AP{g}_2+2B$

Where, P${}_{g1}$ and P${}_{g2}$ are the generated powers of two plants, and A and B are the constants. If the two plants optimally share 1000 MW load at incremental fuel cost of 100 Rs/MWh, the ratio of load shared by plants P₁ and P₂ is

Bus 1 with voltage magnitude V₁ = 1.1 pu is sending reactive power Q₁₂ towards bus 2 with voltage magnitude V₂ = 1 pu through a lossless transmission line of reactance X. Keeping the voltage at bus 2 fixed at 1 pu, magnitude of voltage at bus 1 is changed, so that the reactive power Q₁₂ sent from bus 1 is increased by 20%. Real power flow through the line under both the conditions is zero. The new value of the voltage magnitude, V₁, in pu (rounded off to 2 decimal places), at bus 1 is ________.

Suppose I${}_A$, I${}_B$ and I${}_C$ are a set of unbalanced current phasors in a three-phase system. The phase-B zero-sequence current I${}_{B0}$ = 0.1 ∠0° p.u. If phase-A current I${}_A$ = 1.1 ∠0° p.u. and phase-C current I${}_C$ = (1 ∠120° + 0.1) p.u. then I${}_B$ in p.u. is