GATE 2024 Power System Rank Booster Quiz 9

The line impedances of 3-phase, transmission line are Z_aa = j50Ω, Z_ab = j10Ω, Z_nn = j80Ω, Z_an = j15Ω. Calculate the self and mutual impedance of the system as well as sequence impedances of the system.

(1) Z_s = j50Ω, Z_m = j10Ω, Z⁽⁰⁾ = j80Ω

(2) Z_s = j100Ω, Z⁽⁰⁾ = j220Ω

(3) Z_m = j60Ω, Z⁽¹⁾ = Z⁽²⁾ = j40

(4) Z_m = j10Ω, Z⁽¹⁾ = j40

In a large, interconnected power system, consider three buses having short circuits capacities: (1) 2000 MVA, (2) 1500 MVA and (3) 1200 MVA respectively. The voltage of all the buses are 1 p.u. If a three-phase fault takes place on bus ‘2’, the change in bus voltage is described as

A 6.6 kV, 3-phase, 10 MVA alternator has positive, negative and zero sequence reactance as j0.1 p.u, j0.05 p.u and j0.045 p.u. A double line to ground fault occurs, then the magnitude of positive sequence voltage is _______.

An alternator is having self-inductance of the winding j0.1 p.u. and mutual inductance is j0.03 p.u. The sequence impedances are:

(1) Z_g⁽⁰⁾ = 0.07 p.u. = 0.04 p.u.

(2) Z_g⁽¹⁾ = Z_g⁽²⁾ = 0.07 p.u. Z_g⁽⁰⁾ = 0.16 p.u. = 0.13 p.u.

(3) Z_g⁽⁰⁾ = 0.04 p.u. = 0.13 p.u.

(4) Z_g⁽¹⁾ = Z_g⁽²⁾ = 0.13

There are three generator connected in parallel for each positive, negative, zero sequence reactance are 0.5 p.u, 0.4 p.u and 0.25 p.u respectively. For pre-fault voltage of 1 p.u, single line to ground fault current magnitude if fault is occurred at terminal of generator is ________.

The zero-sequence circuit of a three-phase transformer as shown in figure below is

A 45 MVA, 13.2 kV alternator with solidly grounded neutral has a sub-transient reactance of 0.25 p.u. The negative and zero sequence reactance’s are 0.35 p.u. and 0.1 p.u. respectively. A single line to ground fault occurs at the terminals of an unloaded alternator the fault current is ________.