“For there to be a zero-sequence current to flow in a three-phase circuit there must be...
“For there to be a zero-sequence current to flow in a
three-phase circuit there must be a connection to ground.” (true or
false statement?)
a. True
b. False
Homework Answers
Zero sequence current: The unbalanced current flows in the circuit during the earth fault is known as the zero sequence current or the DC component of the fault current.
Note that this current flows only when there is a path for it, that is neutral wire connected to ground.
Thus the given statement is true.....
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“For there to be a zero-sequence current to flow in a
three-phase circuit there must be...
52. In three-phase power systems, the delivered power a. falls to zero three times per cycle...
52. In three-phase power systems, the delivered power a. falls to zero three times per cycle b. falls to zero once per cycle c. never falls to zero d. none of the above 53. The three-phase connection in which one end of each of the windings are connected together is called the connection. a. delta b. wye c. open delta d. open wye 54. In a three phase connection, the voliage meaured direety across one of the winings is the...
Q2. (a) For the following system, please draw the complete positive-sequence, negative-sequence and zero-sequence network connection (phase A) for the double line-to-ground faults (phases B and C to...
Q2. (a) For the following system, please draw the complete positive-sequence, negative-sequence and zero-sequence network connection (phase A) for the double line-to-ground faults (phases B and C to ground faults) at bus M. XP XLu Eaz EGs Figure Q2. (b) For double line-to-ground faults at point M, please find the positive-sequence cuurent of phase A. The parameters are as follows: Prefault voltage Egi-120, Ea-10 E-10 (Per Unit) Parameters (Per Unit): Generators: Xa-X,-X,o = 0.2 , Xa,' = X,-= XG2-0.2 Transformers....
QUESTION 3. (a) The positive-, negative- and zero-sequence reactances of a 20-MVA, 13.2-LV synchronous generator are...
QUESTION 3. (a) The positive-, negative- and zero-sequence reactances of a 20-MVA, 13.2-LV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A line-to-ground fault occurs on phase a. Neglecting all the resistances, determine the fault current. Assume V, = 120° pu. (b) Explain why a bolted single-line-to-ground fault at the sending end of a transmission line might be higher than the bolted three-phase short circuit on the same...
1. For the following three-phase network, draw the positive sequence diagram and the zero sequenc...
1. For the following three-phase network, draw the positive sequence diagram and the zero sequence diagram. Choose a system base of 120 MVA, 154 KV in the L1 portion of the system. Next, find the thevenin impedance at Bus A (in pu) for both the positive sequence and zero sequence diagrams G 1: 1 3.2KV, 80 MVA, XI-X2-9%, X0-6%, xn-4% on gen rating T1: 1 3.8KV delta/161 KV Wye, 60 MVA, X-9% T1 Bus A L1 G1 Xn
1. For...
The zero-, positive-, and negative-sequence bus impedance matrices for a three bus power system are given...
The zero-, positive-, and negative-sequence bus impedance matrices for a three bus power system are given below 5. T0.10 0.15 0.121 Bu0.15 0.10 0.08 pu [0.16 0.10 0.15] Lo.15 0.14 0.30 0.12 0.08 0.35 ZBus ZBus0.10 0.20 0.14 pu Determine the per unit fault current and the bus voltages during fault for (a) A bolted three-phase fault at bus 2. (b) A bolted single line-to-ground fault at bus 2. (c) A bolted line-to-line fault at bus 2 (d) A bolted...
A three-phase unbalanced source with the following phase to neutral voltages: 300-120 20090 10ol-30 1001-30 is applied to the circuit of balanced star. The star common point is connected to the i...
A three-phase unbalanced source with the following phase to neutral voltages: 300-120 20090 10ol-30 1001-30 is applied to the circuit of balanced star. The star common point is connected to the impedance of Z, -2j The load series impedance per phase is Z, -10+40j a) The load sequence impednace matrix Zo b) The symmetrical components of voltage. (magnitude and angle) ground through Determine
A three-phase unbalanced source with the following phase to neutral voltages: 300-120 20090 10ol-30 1001-30 is applied...
Questions from protective Relaying course Need help ... Thank you In Figure 1.1, a three-phase short circuit at bus f c...
Questions from protective Relaying course
Need help ... Thank you
In Figure 1.1, a three-phase short circuit at bus f can be represented c) (6) as connection through a transition impedance Zf to the ground. The faulted network can be decomposed as two parts. If the elements of impedance matrix of the network are given, G is the set of buses connected with current sources, what is the voltage of any bus i before the fault happens? d) With the...
(15 points) In a balanced three-phase wye-delta system, the source has a positive (abc) phase sequence...
(15 points) In a balanced three-phase wye-delta system, the source has a positive (abc) phase sequence and a phase voltage of Van 200VrmsZ - 30°. If the line impedance is zero and the line current is LaA -6ArmsZ- 65°, find the load impedance per phase in the delta. AB AB Arms
1.) For a balanced three-phase wye-wye circuit. For a negative or ‘acb' sequence, SOURCE с LOAD...
1.) For a balanced three-phase wye-wye circuit. For a negative or ‘acb' sequence, SOURCE с LOAD a + Van n 5k b If Van = 100 VAC (effective voltage) a. Find the other phase voltages, Von and Vcn, including phase angles. b. Find the Line Voltages, including phase angles. C. If Zy = 5k12, find the magnitude of the phase and line currents. note: review the notes from Wednesday/Thursday on which measurements are phase, line, voltages and currents.
(10 points) For the power system shown below, sketch the sequence circuit connections for a 02,...
(10 points) For the power system shown below, sketch the sequence circuit connections for a 02, phase A to ground fault at bus B, and develop the equation for calculating the fault current in sequence coordinates. The sequence impedances of the generator and transformer are shown in the figure. T1 B (GENHH OH SLG FAULT Generator: Zs1 = Zs2, Zso, Y-grounded T1: Zy1 = Z12 = Zto, Delta-Wye Grounded Fault: Phase A to Ground, Z = 0
52. In three-phase power systems, the delivered power a. falls to zero three times per cycle b. falls to zero once per cycle c. never falls to zero d. none of the above 53. The three-phase connection in which one end of each of the windings are connected together is called the connection. a. delta b. wye c. open delta d. open wye 54. In a three phase connection, the voliage meaured direety across one of the winings is the...
Q2. (a) For the following system, please draw the complete positive-sequence, negative-sequence and zero-sequence network connection (phase A) for the double line-to-ground faults (phases B and C to ground faults) at bus M. XP XLu Eaz EGs Figure Q2. (b) For double line-to-ground faults at point M, please find the positive-sequence cuurent of phase A. The parameters are as follows: Prefault voltage Egi-120, Ea-10 E-10 (Per Unit) Parameters (Per Unit): Generators: Xa-X,-X,o = 0.2 , Xa,' = X,-= XG2-0.2 Transformers....
QUESTION 3. (a) The positive-, negative- and zero-sequence reactances of a 20-MVA, 13.2-LV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A line-to-ground fault occurs on phase a. Neglecting all the resistances, determine the fault current. Assume V, = 120° pu. (b) Explain why a bolted single-line-to-ground fault at the sending end of a transmission line might be higher than the bolted three-phase short circuit on the same...
1. For the following three-phase network, draw the positive sequence diagram and the zero sequence diagram. Choose a system base of 120 MVA, 154 KV in the L1 portion of the system. Next, find the thevenin impedance at Bus A (in pu) for both the positive sequence and zero sequence diagrams G 1: 1 3.2KV, 80 MVA, XI-X2-9%, X0-6%, xn-4% on gen rating T1: 1 3.8KV delta/161 KV Wye, 60 MVA, X-9% T1 Bus A L1 G1 Xn
1. For...
The zero-, positive-, and negative-sequence bus impedance matrices for a three bus power system are given below 5. T0.10 0.15 0.121 Bu0.15 0.10 0.08 pu [0.16 0.10 0.15] Lo.15 0.14 0.30 0.12 0.08 0.35 ZBus ZBus0.10 0.20 0.14 pu Determine the per unit fault current and the bus voltages during fault for (a) A bolted three-phase fault at bus 2. (b) A bolted single line-to-ground fault at bus 2. (c) A bolted line-to-line fault at bus 2 (d) A bolted...
A three-phase unbalanced source with the following phase to neutral voltages: 300-120 20090 10ol-30 1001-30 is applied to the circuit of balanced star. The star common point is connected to the impedance of Z, -2j The load series impedance per phase is Z, -10+40j a) The load sequence impednace matrix Zo b) The symmetrical components of voltage. (magnitude and angle) ground through Determine
A three-phase unbalanced source with the following phase to neutral voltages: 300-120 20090 10ol-30 1001-30 is applied...
Questions from protective Relaying course
Need help ... Thank you
In Figure 1.1, a three-phase short circuit at bus f can be represented c) (6) as connection through a transition impedance Zf to the ground. The faulted network can be decomposed as two parts. If the elements of impedance matrix of the network are given, G is the set of buses connected with current sources, what is the voltage of any bus i before the fault happens? d) With the...
(15 points) In a balanced three-phase wye-delta system, the source has a positive (abc) phase sequence and a phase voltage of Van 200VrmsZ - 30°. If the line impedance is zero and the line current is LaA -6ArmsZ- 65°, find the load impedance per phase in the delta. AB AB Arms
1.) For a balanced three-phase wye-wye circuit. For a negative or ‘acb' sequence, SOURCE с LOAD a + Van n 5k b If Van = 100 VAC (effective voltage) a. Find the other phase voltages, Von and Vcn, including phase angles. b. Find the Line Voltages, including phase angles. C. If Zy = 5k12, find the magnitude of the phase and line currents. note: review the notes from Wednesday/Thursday on which measurements are phase, line, voltages and currents.
(10 points) For the power system shown below, sketch the sequence circuit connections for a 02, phase A to ground fault at bus B, and develop the equation for calculating the fault current in sequence coordinates. The sequence impedances of the generator and transformer are shown in the figure. T1 B (GENHH OH SLG FAULT Generator: Zs1 = Zs2, Zso, Y-grounded T1: Zy1 = Z12 = Zto, Delta-Wye Grounded Fault: Phase A to Ground, Z = 0
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