GATE 2022 : Power System Quiz 7

In an isolated neutral system, when a single line to ground fault occurs

Two identical unloaded generators are connected in parallel as shown below. Both the generators are having positive, negative and zero sequence impedance of j0.8 p.u., j0.2 p.u. and 0.3 p.u. respectively. If pre-fault voltage is 1 p.u. for a line to ground fault at the terminals of the generator, the fault current magnitude (in p.u.) is ___________. (Assume neutral impedance, Z_n = j0.02 p.u.)

A 345-kV transmission line a series impedance of (4+j60) Ω and a shunt admittance of j2 × 10^–3 S. Using 100 MVA and the line voltage as base values the per unit admittance of line is ja p.u. The value of ‘a’ is ________.

What is phasor sum of currents I₁ = (10a – a²) and I₂ = –j10 for two complex operators which are individually defined by a³ = 1 and j² = 1?

A 15 MVA, 11 kV, alternator has positive, negative and zero sequence reactance are 0.3 p.u., 0.2 p.u. and 0.05 p.u. respectively. Find the value of resistance to be added in the generator neutral so that the fault current of LG fault does not exceed 1.5 times of rated line current.