MANAVKUMAR SAMJAYKUMAR BHAVSAR_ASSIGNMENT 1_CVG6320

10) In carrier current protection the purpose of the wave trap is for trapping power frequency waves trapping high frequency waves entering into generators/ transformer unit both (a) and (b) none of the above

estion 9 The fault current level of a circuit breaker used in a transmission line with phase voltage 2.2 kV and breaking capacity 50 MVA is yet ......kA. vered -ked out of Flag question estion 10 The voltage between lines in a transmission line is the maximum value of the sine waveform. yet vered Select one: -ked out of O True Flag question O False

Define and draw unit circle. What is the significance of unit circle for system analysis?

1. The subscript d in the generator subtransient reactance refers to: 1. Generator impedance 2. If the available fault current slightly exceeds the breaker published 2. Generator 3. Direct axis 4. 1 and 2 reactance interrupting rating, then it is safe to use the breaker. 1. True | 2. False 3. Maybe 3. The rms symmetrical fault current times an asymmetry factor K, is equal to the ac fault current. | 2. False 4. The most common fault on a 3-phase power system is: 1. True 3. Maybe | 2. DLG 3. L-L 1. SLG 5. All rotating and non-rotating load impedances are usually included in a power system fault study 1. True 2. False 3. Мaybe

Maximum Voltage harmonics Order Vhmax 5 7 11 13 17 19 23 25 6% 5% 3.5% 3% 2% 1.5% 1.5% 1.5% 3) Draw the schematics of a HVDC and of a HVDC light, compare the systems evidencing advantages and disadvantages, describe their inclusion in a Load Flow. 4) Compare the critical distance method and the fault position method, evidencing the equations needed for each of the methods in case of sag due to three phase short circuit.

For the circuit shown, if a symmetrical three-phase fault occurs in node 2, determinea. The short-circuit current in all three phases. b. The voltage at node 1 during the fault.c. The current in generator 1 during the fault. Neglect the prefault currents and consider the reference voltage of the system at 10√3 ??.

Let the system of Figure 1 operating with mechanical input Pm at a steady angle ôo. A three phase fault occurs at the outgoing radial line and hereby the fault is cleared by opening the circuit breaker. Now, find the effect of clearing time on transient stability. Breaker Generator G XL Transformer Fault Pm

Q-5-) 60 Hz generator supplies 0.50 Pmax power to a busbar with infinite power over a conveying line. When a fault occurs, the reactance value between the generator and the infinite bus becomes 400% times the value before the fault. When the fault is isolated, the maximum power that can be transferred generator to the endless bus is 75% of the original (initial) maximum value. Accordingly, using t area criterion method, calculate the critical clearance angle of the system. 00

Voltage sags due to short circuit and earth faults are the cause for the vast majority of equipment problems. Electronics equipment become more susceptible to voltage sag, hence the companies experience production stoppages. Voltage sag analysis is very complex issue. Based on voltage sag randon factors describe on it.

5.26 An unloaded generator with a pre-fault voltage ct 1 pu has the following sequence impedance: Z, = j0. 15 pu, Z, = Z, = j0.25 pu The neutral is grounded with a reactance of 0.05 pu. The fault current in pu for a single-line to ground fault is (a) 3.75 pu (c) 6 pu (b) 4.28 pu (d) 7.25 pu

complet The equivalent reactance of the double circuit line under post fault condition is................than fault condition.

Q5: A generator is connected through a transformer to a synchronous motor. Reduced to the same base, the per unit subtransient reactances of the generator and motor are 0.15 and 0.35, respectively, and the leakage reactance of the transformer is 0.1 per uint. A three-phase fault occurs at the terminals of the motor when the terminal voltage of the generator is 0.9 per uint and the output current of the generator is 1 per unit at 0.8 power factor leading. Find the subtransient current in per unit in the fault, in the generator, and in the motor. Use the terminal voltage of the generator as the reference phasor and obtain the solution (a) by using the internal voltages of the machines and (b) by using Thevenin's theorem.

1 Xine = j0.30 %3D G M X" = j0.15 X" = j0.20 Xiine = j0.30 Xiine = j0.30 %3D 1. Find the Thévenin equivalent looking into bus 3. 2. Calculate the subtransient fault current for a bolted three-phase fault at bus 3. Pre-fault voltage is VF 1Z°, and pre-fault current is neglected. 3. Distribute the fault current between the motor and generator.

If the source impedance at a 13.2 kV distribution substation bus is (0:5 + 1:5) Q per phase, compute the RMS and maximum peak instantaneous value of the fault current, for a balanced three-phase fault. For the system (X/R) ratio of 3.0, the asymmetrical factor is 1.9495 and the time of peak is 7.1 ms (see Problem 1). Comment on the withstanding peak current capability to which all substation electrical equipment need to be designed. Problem 1 Consider the expression for i(f) given by i(t) = v21ms [sin(@t-0-)+ sin 0,.eR/X)] where ez = tan-1 (WL/R). (a) For (X/R) equal to zero and infinity, plot i(f) as a function of (wf). (b) Comment on the DC offset of the fault current waveforms. (c) Find the asymmetrical current factor and the time of peak, tp, in milliseconds, for (X/R) ratios of zero and infinity.

Q3: - A three-phase fault occurs at bus-1 of the network shown in figure below. The pre-fault voltage is 1.05 PU and the pre-fault load current is neglected. (45%) i) determine the bus impedance matrix. ii) calculate the sub-transient fault current and the contribution to the fault current from the transmission line. T1 T2 T.L j0.1 PU 10.1 PU j0.105 PU G jXdg j0.15 PU M jXdm $0.2 PU

A fault which gives rise to symmetrical fault currents (equal faults currents with 120-degree displacement) is called a unsymmetrical fault. Select one:   a. False b. True

Q.3 When a line-to-ground fault occurs, the current in faulted phase 'a' is 100A. The zero-sequence current in phase 'c' is r

Approximately 75 percentage of the fault are either _____ or permanent LG Faults. a. LLG b. Transient c. Simple d. LL

Q: A three phase alternator 100 MVA, 13.5 KV, exposure to types of faults are fallowing: i) Balanced three-phase fault current = 0.437 p.u ii) Line to line fault current = 0.6 p.u iii) Single line to ground fault current = 0.965 The alternator neutral connecting to grounded through the fault reactance j0.15 p.u. Find the x,,x2, xo

The chances of faults in underground system are as compared to overhead system .... O less more above none

Q2: A generator supplies motor through a star-delta transformer. The generator is connected to the star side of transformer. A fault occurs between the motor terminals and the transformer. The symmetrical components of the rubtransient current in motor and transformer toward the fault as table below laz(per unit) j2.0 lao(per unit) j3.0 las (per unit) Motof toward the fault Transformer toward the -0.8-j2.6 0.8-j0.4 j1.0 fault Assume X-X,- X2 for both the motor and gencrator. Describe the type of fault. Find (a) the prefault current, in line a, (b) the subtransient fault current in per unit and (c) the subtransient current in each phase of the gencrator in per unit. Gén. Motor

8.In a line-by-line failure we can expect Immersive reader A) Currents exist in the ground connections. B) The current values at the ground connections are zero. C) Short-circuit currents exist in all three phases. D) The voltages at the fault point with respect to ground are zero in the faulted phases. E) N. A.

Draw the fault current direction both in Current transformer and operating relay coils for internal and external double line to line and double line to ground faults. Do the solve for Restricted Earth Fault Protection system for Alternator Stator Winding. Its a topic of Switchgear protection in power system

7.In a line-to-ground fault we can expect that A) There are no currents to ground. B) The voltages at the fault point with respect to ground are zero in all three phases. C) The current in the faulted phase flows to ground. D) There are short circuit currents in all three phases. E) N. A.

b) A fault occurs at bus 4 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 p.u. and the impedance of the electric arc is neglected. Sequence impedance parameters of the generator, transmission lines, and transformer are given in Figure Q3, where X and Y are the last two digits of your student number. jX(1) j0.1Y p.u. jX2)= j0.1Y p.u. jXko) = j0.1X p.u. V₁ = 120° p.u. V₂ = 120° p.u. (i) (ii) 0 jX(1) = j0.2 p.u. 1 jx(2) j0.2 p.u. 2 jX1(0) = j0.25 p.u. jXT(1) jXT(2) 종 3 j0.1X p.u. JX3(1) j0.1Y p.u. j0.1X p.u. JX3(2) j0.1Y p.u. jXT(0) j0.1X p.u. JX3(0)=j0.15 p.u. 0 = x = 1, jX2(1) j0.2Y p.u. V₁=1/0° p.u. jX(2(2) = j0.2Y p.u. jX2(0) = j0.3X p.u. = V3 = 120° p.u. Figure Q3. Circuit for problem 3b). For example, if your student number is c1700123, then: y = 7 = = jXa(r) = j0.13 p.u., jXa(z) = j0.13 p. u., and jXa(o) = j0.12 p. u. Assuming a balanced excitation, draw the positive, negative and zero sequence Thévenin equivalent circuits as seen from…

b) A fault occurs at bus 4 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 p.u. and the impedance of the electric arc is neglected. Sequence impedance parameters of the generator, transmission lines, and transformer are given in Figure Q3, where X and Y are the last two digits of your student number. V₁ = 120° p.u. V₂ = 120° p.u. jX(1) j0.1Y p.u. jX2)= j0.1Y p.u. jXko) j0.1X p.u. - 0 jX(1) = j0.2 p.u. 1JX(2) = 0.2 p.u. 2 jX1(0) = j0.25 p.u. jX2(1) j0.2 p.u. V₁=1/0° p.u. jX(2(2) = j0.2Y p.u. jX2(0) = j0.3X p.u. = V₂ = 120° p.u. jXT(1) j0.1X p.u. jXT(2) j0.1X p.u. JX3(1) j0.1Y p.u. JX3(2)=j0.1Y p.u. jXT(0) j0.1X p.u. JX3(0)=j0.15 p.u. 0- = 3 = Figure Q3. Circuit for problem 3b). For example, if your student number is c1700123, then: jXa(n) = j0.13 p. u., jXa(z) = j0.13 p. u., and jXa(o) = j0.12 p. u. 4 (i) Assuming a balanced excitation, draw the positive, negative and zero sequence Thévenin equivalent circuits as seen from bus 4. (ii)…

Line to line to line fault is an asymmetrical type of fault in power system which occurs very frequently true false

b) A fault occurs at bus 2 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 p.u. and the impedance of the electric arc is neglected. Sequence impedance parameters of the generator, transmission lines, and transformer are given in Figure Q3, where X and Y are the last two digits of your student number. JX20 /0.1X p.u. jXa2) 0.1X p.u. JX20 j0.2Y p.u. V,= 120° p.u. V, 120° p.u. V, 120° p.u. jX4-70.2X p.u. jX2 j0.2X p.u. jX o 0.2Y p.u. jXncay J0.25 p.u. jXna J0.25 p.u. 3 jXno0.3 p.u. jXTu) /0.2Y p.u. jXra j0.2Y p.u. - j0.2Y p.u. Xp-10.1X p.u. jXa j0.1X p.u. jXp0)- j0.05 p.u. 0 Figure Q3. Circuit for problem 3b). For example, if your student number is c1700123, then: jXac1) = j0.22 p.u., jXac2) = j0.22 p.u., and jXaco) = j0.23 p. u. X-2 Y=8 (iv) Determine the short-circuit fault current for the case when a phase-to- phase fault occurs at bus 2.

Q.3 When a line-to-ground fault occurs, the current in faulted phase 'a' is 100A. The zero-sequence current in phase 'c' is

A fault which gives rise to symmetrical fault currents (equal faults currents with 120-degree displacement) is called a symmetrical fault. Select one: a. False O b. True

A 30kV, 50MVA generator having a solidly grounded neutral and Z1 = 0.25pu, Z2=0.15pu and Z0=0.05pu. a. Calculate the fault current and voltages for a single line to ground fault. b. Sketch the phasor diagram for the fault voltages.