2-1: Choose the correct answer: 1. Gas insulated substation (GIS) use following gas for insulation a) CO2 b) Sulfur hexafluoride c) Nitrogen d) Helium 2. Which of the following Busbar arrangement has the best reliability? a) Single Busbar arrangement b) Single Busbar arrangement with sectionalization c) Double Busbar arrangement d) Not of above 3. The Townsends Criterion for Threshold sparking is given as: a) yead b) ead c) ead /y d) y(ead – 1) = 1 = 2 = 1 %3D -

2-1: Choose the correct answer: 1. Gas insulated substation (GIS) use following gas for insulation a) CO2 b) Sulfur hexafluoride c) Nitrogen d) Helium 2. Which of the following Busbar arrangement has the best reliability? a) Single Busbar arrangement b) Single Busbar arrangement with sectionalization c) Double Busbar arrangement d) Not of above 3. The Townsends Criterion for Threshold sparking is given as: a) yead b) ead c) ead /y d) y(ead – 1) = 1 = 2 = 1 %3D -

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter7: Symmetrical Faults

Section: Chapter Questions

Problem 7.6P

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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 3 of the network shown in Figure Q4. 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, transformer and load are given in Figure Q4. V₁ = 120° p.u. V₂ = 120° p.u. V₂ = 1/0° p.u. V₂= 120° p.u. jXj0.1 p.u. JX2) 0.1 p.u. jX0j0.15 p.u. jXn-j0.2 p.u. 1 JX(2)-j0.2 p.u. 2 jX)=j0.25 p.u. JX20-10.15 p.u. jXa(z)-j0.2 p.u. 4 jX2(0)=j0.2 p.u. jXT(1) j0.1 p.u. jXT(2)=j0.15 p.u. jXT(0)=j0.1 p.u. Figure Q4. Circuit for problem 4b). = jXj0.1 p.u. j0.1 p.u. - JX(2) JXL(0) 10.1 p.u. = (i) Assuming a balanced excitation, draw the positive, negative and zero sequence Thévenin equivalent circuits as seen from bus 3. (ii) Determine the positive sequence fault current for the case when a three- phase-to-ground fault occurs at bus 3 of the network. (iii) Determine the short-circuit fault current for the case when a one-phase- to-ground fault occurs at bus…
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
The system values are given below. The bus 1 voltage after fault = 1.5 p.u The bus 2 voltage after fault = 1.2 p.u The line admittance between bus 1 and bus 2 (Y12 ) is = 0.8 p.u The post fault current current flow between bus 1 and 2 is ..............
Q2 Figure Q2 shows a single line diagram of a power system and the associated data of this system are given in Table Q2. The pre-fault load current and A-Y transformer phase shift are neglected. (a) (b) If a Single Line-to-Ground (S-L-G) fault occurs at Bus 5 and the pre-fault voltage is 1.0 pu, calculate the subtransient fault current in Ampere. (c) (d) (e) Using base of 100 MVA and 11 kV at generator G₁, construct the positive sequence, negative sequence and zero sequence networks with their corresponding component values indicated. G₁ Recalculate (b) if the neutral on HV side of T3 is solidly grounded. Repeat part (b) with Line-to-line (L-L) fault. What will happen to L-L fault current in (d) if the neutral on the HV side of T3 is solidly grounded? Bus 1 T₁ Bus 4 Line 1 Line 2 Figure Q2 Bus 5 T2 T3 Bus 2 Bus 3 G₂ G3
b) A fault occurs at bus 4 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 + j0 p.u, and the impedance of the electric arc is neglected (Zf = 0 + j0 p.u.). The positive, negative and zero sequence impedance parameters of the generator, transmission lines and transformer are given in Figure Q3. (i) Determine the positive sequence fault current for the case when a three-phase-to-ground fault occurs at bus 4 of the network (ii) Determine the short-circuit fault current for the case when a one-phase- to-ground fault occurs at bus 4. Recall that phasors can be expressed in terms of their symmetrical components as shown in the picture attached. where F stands for any three-phase quantity (e.g., current, voltage) (iii) Determine the short-circuit fault current for the case when a phase-to-phase fault occurs at bus 4 ReplyForward
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.
Q1. Given Zo = 0.3L60°, Z¡ = 0.17L80° and, Z2 = 0.45L120°. Compute the fault current and voltages for a Double Line-to-Ground Fault. Note that the sequence impedances are in per- unit. This means that the solution for current and voltage will be in per-unit. [1] Note: Formulas for the reference For Double line to ground fault the positive, negative and zero sequence circuits are connected in parallel The sequence networks are interconnected, as shown in Fig. 8.9 Zo To Because the sequence currents sum to one node, it follows that Vo I, =-(I, +1,) The current I, is the voltage drop across Z, in series with the parallel combination of Z, and V, I = Z, + Z, +Z, V2 Fig 8.9
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
Data obtained from a short circuit test on a 132 kV 3-phase circuit breaker with earthed neutral are as follows: -the power factor fault was 0.3. -the recovery voltage was 0.75 of the full line value. -the breaking current was symmetrical. -the restriking transient had a natural frequency of 1600 Hz. Estimate the rate rise of the recovery voltage. Assume that the fault is grounded.
Fill in the blanks 1. Grounding is connecting …….. of electrical equipment to earth. 2. When a …………………………….… fault occurs on an ungrounded neutral system, the potential of the healthy phases rise to the line voltage. 3. The method of reactance grounding is not used because of ……………………… appearing under fault conditions. 4. The cosine of the angle between the ………………………………………. and the ………………………………...…… is called the sending end power factor. 5. The AC power delivered to a load is equal to ………........
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.