GATE 2016 EE (EE2) – Question 48

Power Systems · System stability concepts, Equal area criterion · 2 marks · Numerical answer

The balanced system has generator internal and infinite-bus voltages fixed at 1 pu. Component reactances are shown. A three-phase fault occurs midway along line 2. The ratio of pre-fault to faulted maximum transferable real power is ________.

Diagram for GATE 2016 EE (EE2) question 48

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: 2.20 to 2.35

Explanation

Before the fault, the two transformer-plus-line branches each have reactance 0.1+0.5=0.6 pu. In parallel they give 0.3, and with generator reactance 0.2 the transfer reactance is 0.5 pu.

During the fault the healthy path remains 0.6, while the sending junction has shunt reactance 0.1+0.25=0.35 to the fault. Eliminating that junction gives effective transfer reactance $0.2+0.6+(0.2\cdot0.6)/0.35=1.142857$ pu.

Since Pmax=EV/Xtransfer, the requested ratio is 1.142857/0.5=**2.28571**, in 2.20–2.35.

More System stability concepts, Equal area criterion questions

GATE 2015 EE (EE2) Q26 – The synchronous generator shown feeds an infinite bus through two short lossless lines and…
GATE 2025 EE Q49 – In the system shown below, the generator was initially supplying power to the grid. A…
GATE 2024 EE Q56 – The single line diagram of a lossless system is shown in the figure. The system is…
GATE 2022 EE Q57 – A 20 MVA, 11.2 kV, 4-pole, 50 Hz alternator has an inertia constant of 15 MJ/MVA. If the…
GATE 2021 EE Q29 – An alternator with internal voltage of 1 1 p.u and synchronous reactance of 0.4 p.u is…
GATE 2020 EE Q59 – A cylindrical rotor generator has steady state synchronous reactance of 0.7 pu and…

All System stability concepts, Equal area criterion questions →