Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN: 9781305632134
Author: J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher: Cengage Learning
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Question
Chapter 9, Problem 9.2P
To determine
The Thevenin equivalent for each sequence network as viewed from the fault bus.
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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…
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.
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
Chapter 9 Solutions
Power System Analysis and Design (MindTap Course List)
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- X=2 Y=8arrow_forward1. For this question you are to sketch two transformers (T1 and T2) side by side connected in PARALLEL. Be sure to employ alphanumeric polarity markings for each transformer with the LV windings on the TOP and the HV windings on the BOTTOM. T1 should have ADDITIVE polarity and T2 should have SUBTRACTIVE polarity. Include a source bus voltage [REFERENCE] above the transformers and a single-phase load. Indicate the direction of all voltages with respect to the reference direction. Based on the preceding requirements, provide a complete SCHEMATIC diagram showing how the two transformers should be connected for proper PARALLEL operation.arrow_forwardThe single line diagram of a power system is shown in Figure Q2.1 includinggenerator and transformer winding connection and earthing details. The parametersfor this system have been calculated on a common 100 MVA base and are given inTable Q2.1. All resistances and shunt susceptances are neglected. This systemexperiences a single line to ground fault at a point F on line L1. The point F is at adistance d from Bus 4 along the line L1. The total length l of the line L1 is 50 km.Note that the location of d is not drawn to scale in Figure Q2.1. The fault current atthe fault point F is measured to be 6.106 kA. i) Determine the zero, positive, and negative sequence Thevenin equivalentimpedances as seen at the fault point F. These should be evaluated in per unitand shown as a function of d.ii) Use the sequence impedances calculated in part (i) to determine the distance dof the fault (in km) from Bus 4. It's different from the answer, please don't send itarrow_forward
- 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. Motorarrow_forwardEqual area criteria is a method used to calculate: Select one: O a. None of the answers b. Critical clearing angle and time for transient faults O c. Critical clearing voltage angle for transient faults d. Transient stability current limit O e. Steady state stability power limitsarrow_forwardThree zones of a single-phase circuit are identified in the figure. The zones are connected by transformers T₁ and T2, whose ratings are also shown. Using base values of 100 kVA and 240 volts in zone 1, draw the per-unit circuit and determine the per-unit impedances and the per-unit source voltage. Then calculate the load current both in per-unit and in amperes. Transformer winding resistances and shunt admittance branches are neglected. Zone 1 Zone 2 Vs = 220/0° volts 3---38 T, 30 KVA 240/480 volts M 0.10 p.u. Xoa Xune = 2 fl T T₂ 20 kVA 460/115 volts Xeg = 0.10 p.u. Zone 3 ww Zload = 0.9 - 10.20arrow_forward
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