GATE EE
Power System Analysis
Symmetrical Components and Symmetrical and Unsymmetrical Faults
Previous Years Questions

## Marks 1

The valid positive, negative and zero sequence impedances (in p.u.), respectively, for a 220 kV, fully transported three-phase transmission line, fro...
The series impedance matrix of a short three-phase transmission line in phase coordinates is $$\left[ {\matrix{ {{Z_s}} & {{Z_m}} & {{Z_m}}... The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are 𝑗0.1 pu, j0.05 pu and j0.0... For a fully transposed transmission line A three phase star-connected load is drawing power at a voltage of 0.9 pu and 0.8 power factor lagging. The three phase base power and base current ar... Three phase to ground fault takes place at locations$${F_1}$$and$${F_2}$$in the system shown in the figure. If the fault takes place at locatio... A 2-bus system and corresponding zero sequence network are shown in the figure. The transformers T1 and T2 are connected as ... The sequence components of the fault current are as follows:$${{\rm I}_{positive}} = j1.5\,pu,\,\,{{\rm I}_{negative}} = - j0.5\,\,pu,{{\rm I}...
A 3-phase transmission line is shown in figure: Voltage drop across the transmission line is given by the following equation: $$\left[ {\matrix{ ... For a fault at the terminals of a synchronous generator, the fault current is maximum for a For an unbalanced fault, with paths for zero sequence currents, at the point of fault The positive sequence component of the voltage at the point of fault in a power system is zero for a _________fault. ## Marks 2 The positive, negative and zero sequence impedances of a three phase generator are Z1, Z2 and Z0 respectively. For a line-to-line fault with fault imp... The positive, negative and zero sequence reactances of a wye-connected synchronous generator are 0.2 pu, 0.2 pu, and 0.1 pu, respectively. The generat... A 30 MVA, 3-phase, 50Hz, 13.8 kV, star-connected synchronous generator has positive, negative and zero sequence reactances, 15%, 15% and 5% respective... A sustained three phase fault occurs in the power system shown in the figure. The current and voltage phasors during the fault (on a common reference)... A three phase,$$100MVA,25kV$$generator has solidly grounded neutral. The positive, negative, and the zero sequence reactance's of the... In an unbalanced three phase system phase current$${{\rm I}_a} = 1\angle \left( { - {{90}^0}} \right)\,\,pu,\,\,$$negative sequence current$$\,{{\r...
The zero-sequence circuit of the three phase transformer shown in the figure is ...
Given that: $$\,{V_{s1}} = {V_{s2}} = 1 + j0\,\,p.u,\,\, + ve\,\,$$ sequence impedance are $$\,{Z_{s1}} = {Z_{s2}} = 0.001 + j0.01\,\,p.u\,\,$$ and $... Given that: $$\,{V_{s1}} = {V_{s2}} = 1 + j0\,\,p.u,\,\, + ve\,\,$$ sequence impedance are $$\,{Z_{s1}} = {Z_{s2}} = 0.001 + j0.01\,\,p.u\,\,$$ and$...
Given that: $$\,{V_{s1}} = {V_{s2}} = 1 + j0\,\,p.u,\,\, + ve\,\,$$ sequence impedance are $$\,{Z_{s1}} = {Z_{s2}} = 0.001 + j0.01\,\,p.u\,\,$$ and \$...
Suppose we define a sequence transformation between ''a-b-c'' and ''p-n-0''' variables as follows: $$\left[ {\matrix{ {{f_a}} \cr {{f_b}} \cr... Three identical star connected resistors of$$1.0p.u$$are connected to an unbalanced$$3$$phase supply. The load neutral is isolated. The symme... The parameters of transposed overhead transmission line are given as: self reactance$${X_s} = 0.4\,\,\Omega /km$$and Mutual reactance$$\,{X_m} = 0....
At a $$220$$ kV substation of a power system, it is given that the three-phase fault level is $$4000$$ MVA and single-line to ground fault level is $$... At a$$220$$kV substation of a power system, it is given that the three-phase fault level is$$4000$$MVA and single-line to ground fault level is$$...
A $$3$$-phase generator rated at $$110$$ MVA, $$11$$ kV is connected through circuit breakers to a transformer. The generator is having direct axis...
A 3-phase transmission line supplies $$\Delta -$$ connected load Z. The conductor $$'c'$$ of the line develops an open circuit fault as shown in fig...
A 500 MVA, 50 Hz, 3-phase turbo-generator produces power at 22 kV. Generator is Y-connected and its neutral is solidly grounded. Its sequence reactanc...
A 20-MVA, 6.6-kV, 3-phase alternator is connected to a 3-phase transmission line. The per unit positive sequence, negative sequence and zero sequence ...
A three-phase alternator generating unbalanced voltages is connected to an unbalanced load through a 3-phase transmission line as shown in figure. The...
A generator is connected to a transformer which feeds another transformer through a short feeder. The zero sequence impedance values are expressed in ...
A $$50$$ Hz alternator is rated $$500$$ $$MVA,$$ $$20$$ $$kV,$$ with $${X_d} = 1.0$$ per unit and $$X'{'_d} = 0.2$$ per unit. It supplies a purely res...
The severity of line-to-ground and three phase faults at the terminals of an unloaded synchronous generator is to be same. If the terminal voltage is ...
For the network shown in figure the zero sequence reactances in p.u. are indicated. The zero sequence driving point reactance of the node 3 is ...

## Marks 5

A single line-to-ground fault occurs on an unloaded generator in phase a positive, negative, and zero sequence impedances of the generator are j0.25 p...
For the configuration shown in figure, the breaker connecting a large system to bus $$2$$ is initially open. The system $$3$$-phase fault level at bus...
Determine the magnitudes of the symmetrical components ($${{{\rm I}_{R1}},\,{{\rm I}_{R2}}\,}$$ and $${{{\rm I}_{R0}}}$$) of the currents in a three p...
Determine the required MVA rating of the circuit breaker CB for the system shown in given figure. Consider the grid as infinite bus. Choose 6 MVA as b...
In a power-system, the $$3$$-phase fault MVA is always higher than the single-line-ground fault MVA at a bus (State True or False)
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