35 + Interview Questions in Power Systems Page 1 InterviewSolution

1.	A 30 MVA, 3-phase, 50 Hz, 13.8 kV, star-connected synchronous generator has positive, negative and zero sequence reactances, 15%, 15% and 5% respectively. A reactance (Xn) is connected between the neutral of the generator and ground. A double line to ground fault takes place involving phase 'b' and 'c' with a fault impendance of j0.1 p.u.. The value of xn(in p.u.) that will limit the positive sequence generator current to 4270 A is 1.07
Answer» A 30 MVA, 3-phase, 50 Hz, 13.8 kV, star-connected synchronous generator has positive, negative and zero sequence reactances, 15%, 15% and 5% respectively. A reactance (X $_{n}$ ) is connected between the neutral of the generator and ground. A double line to ground fault takes place involving phase 'b' and 'c' with a fault impendance of j0.1 p.u.. The value of x $_{n}$ (in p.u.) that will limit the positive sequence generator current to 4270 A is 1.07

Discussion

2.	Consider the network shown in the figure. The bus numbers and impedances are marked. A 3−ϕ short circuit fault occurs at bus 2. The subtransient current of the fault in per unit is ___.0.33
Answer» Consider the network shown in the figure. The bus numbers and impedances are marked. A $3 - ϕ$ short circuit fault occurs at bus 2. The subtransient current of the fault in per unit is ___. 0.33

Discussion

3.	A 3-phase, 50 Hz, synchronous generator has rating 200 MVA, The Kinetic energy of the machine at synchronous speed is 800 MJ. The machine is running steadily at synchronous speed and delivering 50 MW power at power angle of 10 electrical degrees. If the load is suddenly removed, assuming the acceleration is constant for 8 cycles, the value of power angle after 4 cycles is ___________electrical degrees. 11.81
Answer» A 3-phase, 50 Hz, synchronous generator has rating 200 MVA, The Kinetic energy of the machine at synchronous speed is 800 MJ. The machine is running steadily at synchronous speed and delivering 50 MW power at power angle of 10 electrical degrees. If the load is suddenly removed, assuming the acceleration is constant for 8 cycles, the value of power angle after 4 cycles is ___________electrical degrees. 11.81

Discussion

4.	The incremental cost characteristic of two plant systems are IC1=1.0P1+85Rs/MWhr IC2=1.2P2+72Rs/MWhrwhere P1 and P2 are in MW. The loss coefficient matrix in MW is (0.012−0.001−0.0010.04] the optimum scheduling for λ=150Rs/MWhr will be
Answer» The incremental cost characteristic of two plant systems are $I C_{1} = 1.0 P_{1} + 85 R s / M W h r$ $I C_{2} = 1.2 P_{2} + 72 R s / M W h r$ where $P_{1}$ and $P_{2}$ are in MW. The loss coefficient matrix in MW is $(\begin{matrix} 0.012 & - 0.001 - 0.001 & 0.04 \end{matrix}]$ the optimum scheduling for $λ = 150 R s / M W h r$ will be

4.

The incremental cost characteristic of two plant systems are IC1=1.0P1+85Rs/MWhr IC2=1.2P2+72Rs/MWhrwhere P1 and P2 are in MW. The loss coefficient matrix in MW is (0.012−0.001−0.0010.04] the optimum scheduling for λ=150Rs/MWhr will be

Answer»

The incremental cost characteristic of two plant systems are $I C_{1} = 1.0 P_{1} + 85 R s / M W h r$ $I C_{2} = 1.2 P_{2} + 72 R s / M W h r$

where $P_{1}$ and $P_{2}$ are in MW. The loss coefficient matrix in MW is $(\begin{matrix} 0.012 & - 0.001 - 0.001 & 0.04 \end{matrix}]$ the optimum scheduling for $λ = 150 R s / M W h r$ will be

Discussion

5.	Two generating units rated 300 MW and 400 MW have governor speed regulation of 6% and 4% respectively from no load to full load. Both the generating units are operating in parallel to share a load of 600 MW. Assuming free governor action the load shared by the larger unit is 400
Answer» Two generating units rated 300 MW and 400 MW have governor speed regulation of 6% and 4% respectively from no load to full load. Both the generating units are operating in parallel to share a load of 600 MW. Assuming free governor action the load shared by the larger unit is 400

Discussion

6.	A balanced delta connected load is fed from a 3-ϕ supply. For which, the phase c is open circuited. The currents in the lines are shown. The magnitude of Ib1 is______A.5.77
Answer» A balanced delta connected load is fed from a 3- $ϕ$ supply. For which, the phase c is open circuited. The currents in the lines are shown. The magnitude of $I_{b 1}$ is______A. 5.77

Discussion

7.	A 50 Hz generator is delivering 60% of power that it is capable of delivering through a transmission line to an infinite bus. A fault occurs that increases the reactance between the generator and the infinite bus to 400% of the value before the fault. When fault is isolated, the maximum power that can be delivered is 75% of the original maximum value. For this condition critical clearing angle (in degres) is
Answer» A 50 Hz generator is delivering 60% of power that it is capable of delivering through a transmission line to an infinite bus. A fault occurs that increases the reactance between the generator and the infinite bus to 400% of the value before the fault. When fault is isolated, the maximum power that can be delivered is 75% of the original maximum value. For this condition critical clearing angle (in degres) is

Discussion

8.	For the power system shown below, specification of the components are as follows :G1=11 kV,40 MVA,X=5%T1=11kV33kV,80 MVA, X=10%: T2=33kV11kV,80 MVA, X=10%M1=11 kV, 40 MVA X=5%Line reactance X=50 ΩThe reactance diagram on base MVA=80 MVA is
Answer» For the power system shown below, specification of the components are as follows : $G_{1} = 11 k V, 40 M V A, X = 5 %$ $T_{1} = \frac{11 k V}{33 k V}, 80 M V A, X = 10 % : T_{2} = \frac{33 k V}{11 k V}, 80 M V A, X = 10 %$ $M_{1} = 11 k V, 40 M V A X = 5 %$ $L i n e r e a c t a n c e X = 50 Ω$ $T h e r e a c t a n c e d i a g r a m o n b a s e M V A = 80 M V A i s$

Discussion

9.	In a system, there are two generators operating in parallel. One generator, of rating 250 MVA, has an inertia constant of 6 MJ/MVA while the other generator of 150 MVA has an inertia constant of 4 MJ/MVA. The inertia constant for the combined system on 100 MVA common base is MJ/MVA.21
Answer» In a system, there are two generators operating in parallel. One generator, of rating 250 MVA, has an inertia constant of 6 MJ/MVA while the other generator of 150 MVA has an inertia constant of 4 MJ/MVA. The inertia constant for the combined system on 100 MVA common base is MJ/MVA. 21

Discussion

10.	A transmission line has 0.1 pu impedance on a base of 132 kV, 100 MVA. The pu impedance on a base of 220 kV, 50 MVA is ____pu.0.018
Answer» A transmission line has 0.1 pu impedance on a base of 132 kV, 100 MVA. The pu impedance on a base of 220 kV, 50 MVA is ____pu. 0.018

Discussion

11.	The fuel inputs per hour of two generators delivering 200 MW are as follows: F1=20P1+0.05P21+50 Rs per hour, F2=16P2+0.1P22+40 Rs per hourThe limits of generators are 20≤P2≤60MW; 40≤P1≤150MWFor economic generation P1 and P2 should be
Answer» The fuel inputs per hour of two generators delivering 200 MW are as follows: $F_{1} = 20 P_{1} + 0.05 P_{1}^{2} + 50$ Rs per hour, $F_{2} = 16 P_{2} + 0.1 P_{2}^{2} + 40$ Rs per hour The limits of generators are $20 \leq P_{2} \leq 60 M W;$ $40 \leq P_{1} \leq 150 M W$ For economic generation $P_{1}$ and $P_{2}$ should be

Discussion

12.	The positive , negative and zero sequence impedance of 3−ϕ generator are 0.4 pu, 0.3 pu and 0.2 pu respectively. For a line to line fault with fault impedance Zf and fault current is If1=0.2If, where If is the fault current with zero fault impedance, then value of Zf will be ___ pu.2.8
Answer» The positive , negative and zero sequence impedance of $3 - ϕ$ generator are 0.4 pu, 0.3 pu and 0.2 pu respectively. For a line to line fault with fault impedance $Z_{f}$ and fault current is $I_{f 1} = 0.2 I_{f}$ , where $I_{f}$ is the fault current with zero fault impedance, then value of $Z_{f}$ will be ___ pu. 2.8

Discussion

13.

The line reactance of a power system network are as follows: From BusTo BusReactance 0 1 0.3 p.u. 1 2 0.5 p.uThe bus impedance matrix with '0' as reference bus is,

Answer»

The line reactance of a power system network are as follows:

From Bus	To Bus	Reactance
0	1	0.3 p.u.
1	2	0.5 p.u

The bus impedance matrix with '0' as reference bus is,

Discussion

14.	A 50 MVA, 10 kV, 50 Hz, star-connected, unloaded three-phase alternator has a synchronous reactance of 1 p.u. and sub-transient reactance of 0.2 p.u. If a 3-phase short circuit occurs close to the generator terminals, the ratio of initial and final values of the sinusoidal component of the short circuit current is 5
Answer» A 50 MVA, 10 kV, 50 Hz, star-connected, unloaded three-phase alternator has a synchronous reactance of 1 p.u. and sub-transient reactance of 0.2 p.u. If a 3-phase short circuit occurs close to the generator terminals, the ratio of initial and final values of the sinusoidal component of the short circuit current is 5

Discussion

15.

Line NoFrom BusTo BusReactance1010.2 pu2120.4 pubus impedance matrix with '0' as reference bus is

Answer»

Line No	From Bus	To Bus	Reactance
1	0	1	0.2 pu
2	1	2	0.4 pu

bus impedance matrix with '0' as reference bus is

Discussion

16.	A three bus network is shown in the figure below indicating the p.u. impedances of each element.The bus admittance matrix, Y-bus, of the network is
Answer» A three bus network is shown in the figure below indicating the p.u. impedances of each element. The bus admittance matrix, Y-bus, of the network is

Discussion

17.	The synchronous generator shown in the figure is supplying active power to an infinite bus via two short lossless transmission lines, and is initially in steady state. The mechanical power input to the generator and the voltage magnitude E are constant. If one line is tripped at time t1 by opening the circuit breakers at the two ends (although there is no fault), then it is seen that the generator undergoes a stable transient. Which one of the following waveforms of the rotor angle δ shows the transient correctly?
Answer» The synchronous generator shown in the figure is supplying active power to an infinite bus via two short lossless transmission lines, and is initially in steady state. The mechanical power input to the generator and the voltage magnitude E are constant. If one line is tripped at time $t_{1}$ by opening the circuit breakers at the two ends (although there is no fault), then it is seen that the generator undergoes a stable transient. Which one of the following waveforms of the rotor angle $δ$ shows the transient correctly?

Discussion

18.	A 3-phase , 2-pole, 50 Hz, synchronous generator has a rating of 250 MVA, 0.8 pf lagging. The kinetic energy of the machine at synchronous speed is 1000 MJ. The machine is running steadily at synchronous speed and delivering 60 MW power at a power angle of 10 electrical degrees. If the load is suddenly removed, assuming the acceleration is constant for 10 cycles, the value of the power angle after 5 cycles is electrical degrees is.12.7
Answer» A 3-phase , 2-pole, 50 Hz, synchronous generator has a rating of 250 MVA, 0.8 pf lagging. The kinetic energy of the machine at synchronous speed is 1000 MJ. The machine is running steadily at synchronous speed and delivering 60 MW power at a power angle of 10 electrical degrees. If the load is suddenly removed, assuming the acceleration is constant for 10 cycles, the value of the power angle after 5 cycles is electrical degrees is. 12.7

Discussion

19.	A power system network with n nodes, Z33 of its bus impedance matrix is j0.5 per unit. Voltage at node 3 is 1.3∠−10o per unit. If a capacitor having reactance of -j3.5 per unit now added to the network between node 3 and the reference node, the current drawn by capacitor per unit is
Answer» A power system network with n nodes, $Z_{33}$ of its bus impedance matrix is j0.5 per unit. Voltage at node 3 is 1.3 $∠ - 10^{o}$ per unit. If a capacitor having reactance of -j3.5 per unit now added to the network between node 3 and the reference node, the current drawn by capacitor per unit is

Discussion

20.	A motor is receiving 25% of the power that it is capable of receiving from an infinite bus, if the load on the motor is doubled, calculate the maximum value of δ during the swinging of the rotor around its new equilibrium position.
Answer» A motor is receiving 25% of the power that it is capable of receiving from an infinite bus, if the load on the motor is doubled, calculate the maximum value of $δ$ during the swinging of the rotor around its new equilibrium position.

Discussion

21.	A sub sequence network of a 3−ϕtransformer is given.Find the type of transformer connection?
Answer» A sub sequence network of a $3 - ϕ$ transformer is given. Find the type of transformer connection?

Discussion

22.	Consider the two power systems shown in Figure A below which are initially not interconnected, and are operating in steady state at the same frequency. Separate load flow solutions are computed individually for the two systems, corresponding to this scenario. The bus voltage phasors so obtained are indicated in figure A. These two isolated systems are now interconnected by a short transmission line as shown in figure B, and it is found that P1=P2=Q1=Q2=0. Figure A Figure BThe bus voltage phase angular difference between generator bus X and generator bus Y after the interconnection is
Answer» Consider the two power systems shown in Figure A below which are initially not interconnected, and are operating in steady state at the same frequency. Separate load flow solutions are computed individually for the two systems, corresponding to this scenario. The bus voltage phasors so obtained are indicated in figure A. These two isolated systems are now interconnected by a short transmission line as shown in figure B, and it is found that $P_{1} = P_{2} = Q_{1} = Q_{2} = 0$ . Figure A Figure B The bus voltage phase angular difference between generator bus X and generator bus Y after the interconnection is

Discussion

23.	A three phase, 200 MVA, 11 kV generator has the following p.u. constants. The generator neutral is solidly grounded X1=X2=3X0=0.30 Ω. The ratio of the fault current due to three phase dead short circuit to that of L-G fault would be _____.0.78
Answer» A three phase, 200 MVA, 11 kV generator has the following p.u. constants. The generator neutral is solidly grounded $X_{1} = X_{2} = 3 X_{0} = 0.30 Ω$ . The ratio of the fault current due to three phase dead short circuit to that of L-G fault would be _____. 0.78

Discussion

24.	A 100 kV, 2 micro sec rectangular surge on a line having a surge impedance of 300 Ω approaches a station at which concentrated earth capacitance is 3000 pF. The maximum value of transmitted value is___kV.178.32
Answer» A 100 kV, 2 micro sec rectangular surge on a line having a surge impedance of 300 $Ω$ approaches a station at which concentrated earth capacitance is 3000 pF. The maximum value of transmitted value is___kV. 178.32

Discussion

25.	A 3-phase power system is represented by one line diagram as shown in the figure below: The ratings of equipments are the following: Genrator (G) : 15 MVA, 6.6 kV, X1 = 15%,X2 = 10%Transformer : 15 MVA, 6.6 kV delta/33 kV star,X1=X2=X0=6%Line reactance : X1=X2=2Ω and X0=6ΩIf a SLG fault occurs on bus bar B, then the fault current is _______ p.u.0
Answer» A 3-phase power system is represented by one line diagram as shown in the figure below: The ratings of equipments are the following: Genrator (G) : 15 MVA, 6.6 kV, $X_{1}$ = 15%, $X_{2}$ = 10% Transformer : 15 MVA, 6.6 kV delta/33 kV star, $X_{1} = X_{2} = X_{0} = 6$ % Line reactance : $X_{1} = X_{2} = 2 Ω a n d X_{0} = 6 Ω$ If a SLG fault occurs on bus bar B, then the fault current is _______ p.u. 0

Discussion

26.	For the given Y-bus matrix, the reactance diagram isYbus=⎡⎢⎣−j10+j5+j5+j5−j20+j10+j5+j10−j10⎤⎥⎦
Answer» For the given Y-bus matrix, the reactance diagram is $Y_{b u s} = ⎡ ⎢ ⎣ \begin{matrix} - j 10 & + j 5 & + j 5 + j 5 & - j 20 & + j 10 + j 5 & + j 10 & - j 10 \end{matrix} ⎤ ⎥ ⎦$

Discussion

27.	A three-phase short-circuit fault occurs at point F. in the system shown in figure below. The fault current is _____________A. 878.5
Answer» A three-phase short-circuit fault occurs at point F. in the system shown in figure below. The fault current is _____________A. 878.5

Discussion

28.	Consider the network shown. Bus numbers and impedances are marked. An element having an impedance of 0.8Ω is connected between bus 2 and reference bus. Z22new becomes ___pu.0.218
Answer» Consider the network shown. Bus numbers and impedances are marked. An element having an impedance of $0.8 Ω$ is connected between bus 2 and reference bus. $Z_{22 n e w}$ becomes ___pu. 0.218

Discussion

29.	Three 6.6 kV, 3-ϕ, 10 MVA alternators are connected to a common bus. Each alternator has a positive negative and zero sequence reactances as 0.15 p.u., 0.1 p.u.,0.05 p.u. respectively. A single line to ground fault occurs at point F, as shown in figure below.If is the fault current when all the alternator neutrals solidy grouned I′f is the fault current when only one neutral is solidly grounded and other two neutrals are isolated. Then the value of \|If−I′f\|=________kA.6.512
Answer» Three 6.6 kV, 3- $ϕ$ , 10 MVA alternators are connected to a common bus. Each alternator has a positive negative and zero sequence reactances as 0.15 p.u., 0.1 p.u.,0.05 p.u. respectively. A single line to ground fault occurs at point F, as shown in figure below. $I_{f}$ is the fault current when all the alternator neutrals solidy grouned $I_{f}^{'}$ is the fault current when only one neutral is solidly grounded and other two neutrals are isolated. Then the value of $\| I_{f} - I_{f}^{'} \| =$ ________kA. 6.512

Discussion

30.	For a power system:Line to line fault current=−j2.5 p.u.3−ϕ fault current =−j5 p.u. The positive and negative sequence reactances are
Answer» For a power system: $L i n e t o l i n e f a u l t c u r r e n t = - j 2.5 p . u .$ $3 - ϕ f a u l t c u r r e n t = - j 5 p . u .$ The positive and negative sequence reactances are

Discussion

31.	A cylindrical rotor synchronous generator has steady state synchronous reactance of 0.7 pu and subtransient reactance of 0.2 pu. It is operating at (1+ j0) pu terminal voltage with an internal emf of (1 + j0.7)pu. Following a three-phase solid short circuit fault at the terminal of the generator, the magnitude of the subtransient internal emf in p.u (rounded off to 2 decimal places) is 1.02
Answer» A cylindrical rotor synchronous generator has steady state synchronous reactance of 0.7 pu and subtransient reactance of 0.2 pu. It is operating at (1+ j0) pu terminal voltage with an internal emf of (1 + j0.7)pu. Following a three-phase solid short circuit fault at the terminal of the generator, the magnitude of the subtransient internal emf in p.u (rounded off to 2 decimal places) is 1.02

Discussion

32.	In a load flow problem solved by Newton-Raphson method with polar coordinates, the size of the Jacobian is 100×100. If there are 20 PV buses in addition to PQ buses and a slack bus, the total number of buses in the system is 61
Answer» In a load flow problem solved by Newton-Raphson method with polar coordinates, the size of the Jacobian is $100 \times 100$ . If there are 20 PV buses in addition to PQ buses and a slack bus, the total number of buses in the system is 61

Discussion

33.	A 10-bus power system consists of four generator buses indexed at G1, G2, G3, G4 and six load buses indexed as L1, L2, L3, L4, L5, L6. The generator-bus G1 is considered as slack bus, and the load buses L3 and L4 are voltage controlled buses. The generator at bus G2 cannot supply the required reactive power demand, and hence it is operating at its maximum reactive power limit. The number of non-linear equations required for solving the load flow problem using Newton Raphson method in polar form is14
Answer» A 10-bus power system consists of four generator buses indexed at G1, G2, G3, G4 and six load buses indexed as L1, L2, L3, L4, L5, L6. The generator-bus G1 is considered as slack bus, and the load buses L3 and L4 are voltage controlled buses. The generator at bus G2 cannot supply the required reactive power demand, and hence it is operating at its maximum reactive power limit. The number of non-linear equations required for solving the load flow problem using Newton Raphson method in polar form is 14

Discussion

34.	The series impendance matrix of a short three-phase transmission line in phase coordinates is ⎡⎢⎣ZsZmZmZmZsZmZmZmZs⎤⎥⎦. If the positive sequence impedance is (1 + j10) Ω, and the zero sequence impedance is (4 + j31) Ω, then the imaginary part of Zm(in Ω) is (upto to 2 decimal places).7
Answer» The series impendance matrix of a short three-phase transmission line in phase coordinates is $⎡ ⎢ ⎣ \begin{matrix} Z_{s} & Z_{m} & Z_{m} Z_{m} & Z_{s} & Z_{m} Z_{m} & Z_{m} & Z_{s} \end{matrix} ⎤ ⎥ ⎦$ . If the positive sequence impedance is (1 + j10) $Ω$ , and the zero sequence impedance is (4 + j31) $Ω$ , then the imaginary part of Z $_{m}$ (in $Ω$ ) is (upto to 2 decimal places). 7

Discussion

35.	In the system shown, the generator is delivering 1 p.u. power. The voltage behind transient reactance is 1.05 p.u. and infinite bus voltage is 1 p.u. If the system is subjected to a 3−ϕ fault on point P, the critical clearing angle is______electrical degrees.[H=5 MJ/MVA.f = 50 Hz]
Answer» In the system shown, the generator is delivering 1 p.u. power. The voltage behind transient reactance is 1.05 p.u. and infinite bus voltage is 1 p.u. If the system is subjected to a $3 - ϕ$ fault on point P, the critical clearing angle is______electrical degrees.[H=5 MJ/MVA.f = 50 Hz]

Discussion

Explore topic-wise InterviewSolutions in .

Consider the network shown in the figure. The bus numbers and impedances are marked. A 3−ϕ short circuit fault occurs at bus 2. The subtransient current of the fault in per unit is ___.0.33

The incremental cost characteristic of two plant systems are IC1=1.0P1+85Rs/MWhr IC2=1.2P2+72Rs/MWhrwhere P1 and P2 are in MW. The loss coefficient matrix in MW is (0.012−0.001−0.0010.04] the optimum scheduling for λ=150Rs/MWhr will be

Two generating units rated 300 MW and 400 MW have governor speed regulation of 6% and 4% respectively from no load to full load. Both the generating units are operating in parallel to share a load of 600 MW. Assuming free governor action the load shared by the larger unit is 400

A balanced delta connected load is fed from a 3-ϕ supply. For which, the phase c is open circuited. The currents in the lines are shown. The magnitude of Ib1 is______A.5.77

For the power system shown below, specification of the components are as follows :G1=11 kV,40 MVA,X=5%T1=11kV33kV,80 MVA, X=10%: T2=33kV11kV,80 MVA, X=10%M1=11 kV, 40 MVA X=5%Line reactance X=50 ΩThe reactance diagram on base MVA=80 MVA is

In a system, there are two generators operating in parallel. One generator, of rating 250 MVA, has an inertia constant of 6 MJ/MVA while the other generator of 150 MVA has an inertia constant of 4 MJ/MVA. The inertia constant for the combined system on 100 MVA common base is MJ/MVA.21

A transmission line has 0.1 pu impedance on a base of 132 kV, 100 MVA. The pu impedance on a base of 220 kV, 50 MVA is ____pu.0.018

The fuel inputs per hour of two generators delivering 200 MW are as follows: F1=20P1+0.05P21+50 Rs per hour, F2=16P2+0.1P22+40 Rs per hourThe limits of generators are 20≤P2≤60MW; 40≤P1≤150MWFor economic generation P1 and P2 should be

The positive , negative and zero sequence impedance of 3−ϕ generator are 0.4 pu, 0.3 pu and 0.2 pu respectively. For a line to line fault with fault impedance Zf and fault current is If1=0.2If, where If is the fault current with zero fault impedance, then value of Zf will be ___ pu.2.8

The line reactance of a power system network are as follows: From BusTo BusReactance 0 1 0.3 p.u. 1 2 0.5 p.uThe bus impedance matrix with '0' as reference bus is,

Line NoFrom BusTo BusReactance1010.2 pu2120.4 pubus impedance matrix with '0' as reference bus is

A three bus network is shown in the figure below indicating the p.u. impedances of each element.The bus admittance matrix, Y-bus, of the network is

A power system network with n nodes, Z33 of its bus impedance matrix is j0.5 per unit. Voltage at node 3 is 1.3∠−10o per unit. If a capacitor having reactance of -j3.5 per unit now added to the network between node 3 and the reference node, the current drawn by capacitor per unit is

A motor is receiving 25% of the power that it is capable of receiving from an infinite bus, if the load on the motor is doubled, calculate the maximum value of δ during the swinging of the rotor around its new equilibrium position.

A sub sequence network of a 3−ϕtransformer is given.Find the type of transformer connection?

A three phase, 200 MVA, 11 kV generator has the following p.u. constants. The generator neutral is solidly grounded X1=X2=3X0=0.30 Ω. The ratio of the fault current due to three phase dead short circuit to that of L-G fault would be _____.0.78

A 100 kV, 2 micro sec rectangular surge on a line having a surge impedance of 300 Ω approaches a station at which concentrated earth capacitance is 3000 pF. The maximum value of transmitted value is___kV.178.32

For the given Y-bus matrix, the reactance diagram isYbus=⎡⎢⎣−j10+j5+j5+j5−j20+j10+j5+j10−j10⎤⎥⎦

A three-phase short-circuit fault occurs at point F. in the system shown in figure below. The fault current is _____________A. 878.5

Consider the network shown. Bus numbers and impedances are marked. An element having an impedance of 0.8Ω is connected between bus 2 and reference bus. Z22new becomes ___pu.0.218

For a power system:Line to line fault current=−j2.5 p.u.3−ϕ fault current =−j5 p.u. The positive and negative sequence reactances are

In a load flow problem solved by Newton-Raphson method with polar coordinates, the size of the Jacobian is 100×100. If there are 20 PV buses in addition to PQ buses and a slack bus, the total number of buses in the system is 61

In the system shown, the generator is delivering 1 p.u. power. The voltage behind transient reactance is 1.05 p.u. and infinite bus voltage is 1 p.u. If the system is subjected to a 3−ϕ fault on point P, the critical clearing angle is______electrical degrees.[H=5 MJ/MVA.f = 50 Hz]