Ece421hw04 Abm
-
Author
arturo-barradas -
Category
Documents
-
view
497 -
download
5
Embed Size (px)
description
Transcript of Ece421hw04 Abm

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 1 of 23
Homework #04
1. Problem 3.48 in Glover, Sarma and Overbye
2. Problem 3.49 in Glover, Sarma and Overbye
3. Problem 3.53 in Glover, Sarma and Overbye
4. Problem 3.58 in Glover, Sarma and Overbye
5. Problem 3.59 in Glover, Sarma and Ovebye
6. Problem 3.60 in Glover, Sarma and Ovebye
7. Problem 3.61 in Glover, Sarma and Ovebye
General Definitions
≔ ≔ ≔ ≔
≔ ≔ ≔a ∠1 °120 ≔ 1 ≔Turns 1

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 2 of 23
Problem 01.
1. Problem 3.48 in Glover, Sarma and Overbye
With the same transformer banks as in Problem 3.47, Figure 3.41 shows the one-line diagram of a generator, a step-up transformer bank, a transmission line, a step-down transformer bank, and an impedance load. The generator terminal voltage is 15 kV (line-to-line).
(a) Draw the per-phase equivalent circuit, accounting for phase shifts for positive sequence operation.
(b) By choosing the line-to-neutral generator terminal voltage as the reference, determine the magnitudes of the generator current, transmission-line current, load current, and line-to-line load voltage. Also, find the three-phase complex power delivered to the load.

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 3 of 23
≔ZLoad(( +5 1j))
≔ZLine((100j))
≔XT1_Sph_LV 0.24j
≔XT1_LV ――――XT1_Sph_LV
3=XT1_LV 0.08i
≔XT2_Sph_LV 0.24j
≔XT2_LV ――――XT2_Sph_LV
3=XT2_LV 0.08i

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 4 of 23
(a) Draw the per-phase equivalent circuit, accounting for phase shifts for positive sequence operation.
(b) By choosing the line-to-neutral generator terminal voltage as the reference, determine the magnitudes of the generator current, transmission-line current, load current, and line-to-line load voltage. Also, find the three-phase complex power delivered to the load.
≔Vg_T
⎛⎜⎜⎝
∠――15
‾‾3
°0⎞⎟⎟⎠
=Vg_T(( ∠8.66025 °0 ))
≔ZRight_LV +ZLoad XT2_LV =ZRight_LV(( +5 1.08j))
≔ZRight_HV ⋅ZRight_LV⎛⎝ ⋅10 ‾‾3
⎞⎠
2
=ZRight_HV(( +1500 324j))
≔ZMiddle_HV +ZLine ZRight_HV =ZMiddle_HV(( +1500 424j))
≔ZMiddle_LV ⋅ZMiddle_HV
⎛⎜⎜⎝―――
1
⋅10 ‾‾3
⎞⎟⎟⎠
2
=ZMiddle_LV(( +5 1.41333j))
≔ZLeft_LV +ZMiddle_LV XT1_LV =ZLeft_LV(( +5 1.49333i))
≔Ig_T ―――Vg_T
ZLeft_LV
=Ig_T(( ∠1659.61158 °−16.62913 ))
=||Ig_T|| ⎛⎝ ⋅1.65961 103 ⎞⎠
_______________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 5 of 23
≔ILine ⋅⋅Ig_T ―――1
⋅10 ‾‾3
(( ∠1 °30 )) =ILine(( ∠95.81772 °13.37087 ))
=||ILine|| 95.81772
_______________________/
≔ILoad ⋅⋅⋅ILine 10 ‾‾3 (( ∠1 − °30 )) =ILoad⎛⎝ ∠⋅1.65961 103 °−16.62913 ⎞⎠
=||ILoad|| 1659.61158
_______________________/
≔VLoad ⋅ILoad ZLoad =VLoad⎛⎝ ∠⋅8.46239 103 °−5.3192 ⎞⎠
≔VLoad_LL ⋅VLoad‾‾3
=||VLoad_LL|| 14.65729
_______________________/
≔SLoad ⋅⋅3 VLoad‾‾‾‾ILoad =SLoad
(( +41.31466 8.26293i))
=SLoad(( ∠42.13285 °11.30993 ))
________________________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 6 of 23
Problem 02.
2. Problem 3.49 in Glover, Sarma and Overbye
Consider the single-line diagram of a power system shown in Figure 3.42 with equipment ratings given below:
Generator G1: 50 MVA, 13.2kV, x=0.15 puGenerator G2: 20 MVA, 13.8kV, x=0.15 pu3Ph -Y T1: 80 MVA, 13.2 /165 Y kV, X=0.1 pu3Ph Y- T2: 40 MVA, 165 Y/13.8 kV, X=0.1 puLoad: 40 MVA, 0.8 PF lagging, operating at 150kV
Choose a base of 100 MVA for the system and 132-kV base in the transmission-line circuit. Let the load be modeled as a parallel combination of resistance and inductance. Neglect transformer phase shifts. Draw a per-phase equivalent circuit of the system showing all impedances in per unit.
≔SG1_rat 50 ≔VG1_rat 13.2 ≔xG1_rat 0.15j
≔SG2_rat 50 ≔VG2_rat 13.2 ≔xG2_rat 0.15j
≔ST1_rat 80 ≔VT1_HV_rat 165 ≔xT1_rat 0.1j
≔VT1_LV_rat 13.2
≔ST2_rat 40 ≔VT2_HV_rat 165 ≔xT2_rat 0.1j
≔VT2_LV_rat 13.8

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 7 of 23
≔SLoad_rat(( ∠40 acos ((0.8)))) =SLoad_rat
(( +32 24j)) ≔VLoad_rat 150
≔ZLine1_Ω(( +50 200j)) ≔ZLine2_Ω
(( +25 100j)) ≔ZLine3_Ω(( +25 100j))
≔SB 100 ≔VB_HV 132 ≔ZB_HV ―――VB_HV
2
SB
=ZB_HV 174.24
≔VB_G1 ⋅VB_HV ―――13.2
165=VB_G1 10.56 ≔ZB_G1 ―――
VB_G12
SB
=ZB_G1 1.11514
≔VB_G2 ⋅VB_HV ―――13.8
165=VB_G2 11.04 ≔ZB_G2 ―――
VB_G22
SB
=ZB_G2 1.21882
Change of base
≔xG1 ⋅⋅xG1_rat
⎛⎜⎝―――VG1_rat
VB_G1
⎞⎟⎠
2 ⎛⎜⎝―――
SB
SG1_rat
⎞⎟⎠
=xG1 0.46875j
___________________/
≔xG2 ⋅⋅xG2_rat
⎛⎜⎝―――VG2_rat
VB_G2
⎞⎟⎠
2 ⎛⎜⎝―――
SB
SG2_rat
⎞⎟⎠
=xG2 0.42888j
___________________/
≔xT1 ⋅⋅xT1_rat
⎛⎜⎝――――VT1_HV_rat
VB_HV
⎞⎟⎠
2 ⎛⎜⎝―――
SB
ST1_rat
⎞⎟⎠
=xT1 0.19531i
___________________/
≔xT2 ⋅⋅xT2_rat
⎛⎜⎝――――VT2_HV_rat
VB_HV
⎞⎟⎠
2 ⎛⎜⎝―――
SB
ST2_rat
⎞⎟⎠
=xT2 0.39063i
___________________/
≔ZLine1 ―――ZLine1_Ω
ZB_HV
=ZLine1(( +0.28696 1.14784i))
____________________________/
≔ZLine2 ―――ZLine2_Ω
ZB_HV
=ZLine2(( +0.14348 0.57392i))
____________________________/
≔ZLine3 ―――ZLine3_Ω
ZB_HV
=ZLine3(( +0.14348 0.57392i))
____________________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 8 of 23
≔SLoad ―――SLoad_rat
SB
=SLoad(( +0.32 0.24i))
≔VLoad ―――VLoad_rat
VB_HV
=VLoad 1.13636
≔RLoad_Parallel ――――||VLoad
||2
Re ⎛⎝SLoad⎞⎠
=RLoad_Parallel 4.03538
____________________________/
≔XLoad_Parallel ――――⋅||VLoad
||2
1j
Im ⎛⎝SLoad⎞⎠
=XLoad_Parallel 5.38051j
____________________________/
Draw a per-phase equivalent circuit of the system showing all impedances in per unit.

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 9 of 23
Problem 03.
3. Problem 3.53 in Glover, Sarma and Overbye
The ratings of a three-phase, three-winding transformer are:
Primary: Y connected, 66 kV, 15 MVASecondary: Y connected, 13.2 kV, 10 MVATertiary: connected, 2.3 kV, 5 MVA
Neglecting resistances and exciting current, the leakage reactances are:
XPS= 0.07 per unit on a 15-MVA; 66-kV baseXPT= 0.09 per unit on a 15-MVA; 66-kV baseXST= 0.08 per unit on a 10-MVA; 13.2-kV base
Determine the per-unit reactances of the per-phase equivalent circuit using a base of 15 MVA and 66 kV for the primary.
≔SB 15 ≔VB_P 66 ≔VB_S 13.2 ≔VB_S 2.3
≔XPS_rat 0.07 ≔XPT_rat 0.09 ≔XST_rat 0.08
≔XPS ⋅XPS_rat
⎛⎜⎝―――
SB
15
⎞⎟⎠
=XPS 0.07
≔XPT ⋅XPT_rat
⎛⎜⎝―――
SB
15
⎞⎟⎠
=XPT 0.09
≔XST ⋅XST_rat
⎛⎜⎝―――
SB
10
⎞⎟⎠
=XST 0.12
≔XP ―1
2⎛⎝ −+XPS XPT XST
⎞⎠ ≔XS ―1
2⎛⎝ +−XPS XPT XST
⎞⎠ ≔XT ―1
2⎛⎝ ++−XPS XPT XST
⎞⎠
=XP 0.02 =XS 0.05 =XT 0.07
_____________/ _____________/ _____________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 10 of 23
4. Problem 3.58 in Glover, Sarma and Overbye
A single-phase two-winding transformer rated 90 MVA, 80/120 kV is to be connected as an autotransformer rated 80/200 kV. Assume that the transformer is ideal.
(a) Draw a schematic diagram of the ideal transformer connected as an autotransformer, showing the voltages, currents, and dot notation for polarity.
(b) Determine the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer.
How much of the kVA rating is transferred by magnetic induction?
≔IPrim ―――90
80≔ISec ―――
90
120≔ITot +IPrim ISec
=IPrim 1125 =ISec 750 =ITot 1875
≔VPrim 80 ≔VSec 120 ≔VTot =+VPrim VSec 200
(a) Draw a schematic diagram of the ideal transformer connected as an autotransformer, showing the voltages, currents, and dot notation for polarity.

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 11 of 23
(b) Determine the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer.
≔SAuto ⋅VPrim ITot =SAuto 150000
=⋅VTot ISec 150000
______________________/
How much of the kVA rating is transferred by magnetic induction?
≔STrans_Ind ⋅VPrim IPrim =STrans_Ind 90000
______________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 12 of 23
Problem 05.
5. Problem 3.59 in Glover, Sarma and Overbye
The two parallel lines in Example 3.13 supply a balanced load with a load current of 1.0 /30 degrees per unit. Determine the real and reactive power supplied to the load bus from each parallel line with (a) no regulating transformer, (b) the voltage-magnitude regulating transformer in Example 3.13(a), and (c) the phase-angle-regulating transformer in Example 3.13(b). Assume that the voltage at bus abc is adjusted so that the voltage at bus a'b'c' remains constant at 1.0/ 0 per unit. Also assume positive sequence.
Comment on the e¤ects of the regulating transformers.
≔ILoad(( ∠1 − °30 )) ≔VLoad
(( ∠1 °0 ))
≔SLoad ⋅VLoad‾‾‾‾ILoad =SLoad
(( +0.86603 0.5j))
≔PLoad Re ⎛⎝SLoad⎞⎠ =PLoad 0.86603
≔QLoad Im ⎛⎝SLoad⎞⎠ =QLoad 0.5
≔ZLine_0.20 ⋅0.20j ≔ZLine_0.25 ⋅0.25j

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 13 of 23
Determine the real and reactive power supplied to the load bus from each parallel line with (a) no regulating transformer. Assume that the voltage at bus abc is adjusted so that the voltage at bus a'b'c' remains constant at 1.0/ 0 per unit. Also assume positive sequence.
≔ILine_0.20 ―――――――⋅ILoad ZLine_0.25
+ZLine_0.20 ZLine_0.25
=ILine_0.20(( −0.48113 0.27778i))
≔ILine_0.25 ―――――――⋅ILoad ZLine_0.20
+ZLine_0.20 ZLine_0.25
=ILine_0.25(( −0.3849 0.22222i))
≔SLine_0.20 ⋅VLoad‾‾‾‾‾‾ILine_0.20 =SLine_0.20
(( +0.48113 0.27778i))
=SLine_0.20(( ∠0.55556 °30 ))
≔PLine_0.20 Re ⎛⎝SLine_0.20⎞⎠ =PLine_0.20 0.48113
≔QLine_0.20 Im ⎛⎝SLine_0.20⎞⎠ =QLine_0.20 0.27778
≔SLine_0.25 ⋅VLoad‾‾‾‾‾‾ILine_0.25 =SLine_0.25
(( +0.3849 0.22222i))
=SLine_0.25(( ∠0.44444 °30 ))
≔PLine_0.25 Re ⎛⎝SLine_0.25⎞⎠ =PLine_0.25 0.3849
______________________/
≔QLine_0.25 Im ⎛⎝SLine_0.25⎞⎠ =QLine_0.25 0.22222
______________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 14 of 23
Determine the real and reactive power supplied to the load bus from each parallel line with (b) the voltage-magnitude regulating transformer in Example 3.13(a). Assume that the voltage at bus abc is adjusted so that the voltage at bus a'b'c' remains constant at 1.0/ 0 per unit. Also assume positive sequence.
Comment on the effects of the regulating transformers.
From page 133 in Duncan Glover's Book the admittance parameters of the equation shown below are,
=I1
−I2
⎡⎢⎣
⎤⎥⎦
⋅Y11 Y12
Y21 Y22
⎡⎢⎣
⎤⎥⎦
V1
V2
⎡⎢⎣
⎤⎥⎦
=Y11 YEq =Y12 ⋅−c YEq
=Y21 ⋅−c YEq =Y22 ⋅||c||2 YEq
From page 138 in Duncan Glover's Book the admittance parameters are computed as follows:
≔c 1.05−1 =c 0.95238
The admitance parameters of the regulating transformer in series with line of 0.25j pu are:
≔Y11Line_0.25 ―――1
ZLine_0.25
=Y11Line_0.25 −4j
≔Y22Line_0.25 ⋅||c||2 Y11Line_0.25 =Y22Line_0.25 −3.62812j
≔Y12Line_0.25 ⋅−c Y11Line_0.25 =Y12Line_0.25 3.80952j
≔Y21Line_0.25 ⋅−‾c Y11Line_0.25 =Y21Line_0.25 3.80952j

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 15 of 23
The admitance parameters of the line of 0.20j pu are:
≔Y11Line_0.20 ―――1
ZLine_0.20
=Y11Line_0.20 −5j
≔Y22Line_0.20 Y11Line_0.20 =Y22Line_0.20 −5j
≔Y12Line_0.20 −Y11Line_0.20 =Y12Line_0.20 5j
≔Y21Line_0.20 −Y11Line_0.20 =Y21Line_0.20 5j
Combining both admitances in parallel,
≔Y11 +Y11Line_0.25 Y11Line_0.20 ≔Y12 +Y12Line_0.25 Y12Line_0.20
≔Y21 +Y21Line_0.25 Y21Line_0.20 ≔Y22 +Y22Line_0.25 Y22Line_0.20
=Y11 −9j =Y12 8.80952j
=Y21 8.80952j =Y22 −8.62812j
=I1
−ILoad
⎡⎢⎣
⎤⎥⎦
⋅Y11 Y12
Y21 Y22
⎡⎢⎣
⎤⎥⎦
V1
VLoad
⎡⎢⎣
⎤⎥⎦
Solving for V1
=−ILoad +⋅Y21 V1 ⋅Y22 VLoad
≔V1 ――――――−−ILoad ⋅Y22 VLoad
Y21
=V1(( ∠1.04082 °5.41968 ))

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 16 of 23
≔ILine_0.20 ――――−V1 VLoad
ZLine_0.20
=ILine_0.20(( ∠0.52373 °−20.1976 ))
≔SLine_0.20_b ⋅VLoad‾‾‾‾‾‾ILine_0.20 =SLine_0.20_b
(( +0.49153 0.18082j))
≔PLine_0.20_b Re ⎛⎝SLine_0.20_b⎞⎠ =PLine_0.20_b 0.49153
______________________/
≔QLine_0.20_b Im ⎛⎝SLine_0.20_b⎞⎠ =QLine_0.20_b 0.18082
______________________/
≔ILine_0.25 ――――−V1 ⋅VLoad c
ZLine_0.25
=ILine_0.25(( ∠0.51666 °−40.44026 ))
≔SLine_0.25_b ⋅VLoad‾‾‾‾‾‾‾‾⋅ILine_0.25 c =SLine_0.25_b
(( +0.3745 0.31918j))
≔PLine_0.25_b Re ⎛⎝SLine_0.25_b⎞⎠ =PLine_0.25_b 0.3745
______________________/
≔QLine_0.25_b Im ⎛⎝SLine_0.25_b⎞⎠ =QLine_0.25_b 0.31918
______________________/
or in a simpler way
≔SLine_0.25_b −SLoad SLine_0.20_b =SLine_0.25_b +0.3745 0.31918j
≔PLine_0.25_b Re ⎛⎝SLine_0.25_b⎞⎠ =PLine_0.25_b 0.3745
______________________/
≔QLine_0.25_b Im ⎛⎝SLine_0.25_b⎞⎠ =QLine_0.25_b 0.31918
______________________/

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 17 of 23
Comment on the effects of the regulating transformers.
=SLine_0.20_b(( +0.49153 0.18082j)) =SLine_0.20
(( +0.48113 0.27778j))
=SLine_0.25_b(( +0.3745 0.31918j)) =SLine_0.25
(( +0.3849 0.22222j))
The real power flow in line of 0.20j pu increases a little when comparing to the previous case (from 0.48 to 0.29pu). In contrast the reactive power flow reduces significantly from 0.27 pu to 0.18 pu.
The real power flow in line of 0.25j pu changes a little too when comparing to the previous case (from 0.38 to 0.37 pu) whereas the reactive power flow increases from 0.22 to 0.31 pu, that is to say an approximately increase of 41%.
Therefore the regulating transformer with an increased voltage magnitude will affect mostly the reactive power flow.
Determine the real and reactive power supplied to the load bus from each parallel line with (c) the phase-angle-regulating transformer in Example 3.13(b). Assume that the voltage at bus abc is adjusted so that the voltage at bus a'b'c' remains constant at 1.0/ 0 per unit. Also assume positive sequence.
Comment on the effects of the regulating transformers.
≔c (( ∠1.0 − °3 ))−1
=c (( ∠1 °3 ))
The admitance parameters of the regulating transformer in series with line of 0.25j pu are:
≔Y11Line_0.25 ―――1
ZLine_0.25
=Y11Line_0.25 −4j
≔Y22Line_0.25 ⋅||c||2 Y11Line_0.25 =Y22Line_0.25 −4j
≔Y12Line_0.25 ⋅−c Y11Line_0.25 =Y12Line_0.25(( +−0.20934 3.99452j))
≔Y21Line_0.25 ⋅−c Y11Line_0.25 =Y21Line_0.25(( +−0.20934 3.99452j))

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 18 of 23
The admitance parameters of the line of 0.20j pu are:
≔Y11Line_0.20 ―――1
ZLine_0.20
=Y11Line_0.20 −5j
≔Y22Line_0.20 Y11Line_0.20 =Y22Line_0.20 −5j
≔Y12Line_0.20 −Y11Line_0.20 =Y12Line_0.20 5j
≔Y21Line_0.20 −Y11Line_0.20 =Y21Line_0.20 5j
Combining both admitances in parallel,
≔Y11 +Y11Line_0.25 Y11Line_0.20 ≔Y12 +Y12Line_0.25 Y12Line_0.20
≔Y21 +Y21Line_0.25 Y21Line_0.20 ≔Y22 +Y22Line_0.25 Y22Line_0.20
=Y11 −9j =Y12 +−0.20934 8.99452j
=Y21 +−0.20934 8.99452j =Y22 −9j
=I1
−ILoad
⎡⎢⎣
⎤⎥⎦
⋅Y11 Y12
Y21 Y22
⎡⎢⎣
⎤⎥⎦
V1
VLoad
⎡⎢⎣
⎤⎥⎦
Solving for V1
=−ILoad +⋅Y21 V1 ⋅Y22 VLoad
≔V1 ――――――−−ILoad ⋅Y22 VLoad
Y21
=V1(( ∠1.06029 °3.87542 ))

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 19 of 23
≔ILine_0.20 ――――−V1 VLoad
ZLine_0.20
=ILine_0.20(( ∠0.46054 °−38.92064 ))
≔SLine_0.20_b ⋅VLoad‾‾‾‾‾‾ILine_0.20 =SLine_0.20_b
(( +0.35831 0.28933j))
≔PLine_0.20_b Re ⎛⎝SLine_0.20_b⎞⎠ =PLine_0.20_b 0.35831
______________________/
≔QLine_0.20_b Im ⎛⎝SLine_0.20_b⎞⎠ =QLine_0.20_b 0.28933
______________________/
≔SLine_0.25_b −SLoad SLine_0.20_b =SLine_0.25_b +0.50771 0.21067j
≔PLine_0.25_b Re ⎛⎝SLine_0.25_b⎞⎠ =PLine_0.25_b 0.50771
______________________/≔QLine_0.25_b Im ⎛⎝SLine_0.25_b
⎞⎠ =QLine_0.25_b 0.21067
______________________/
Comment on the effects of the regulating transformers.
=SLine_0.20_b(( +0.35831 0.28933j)) =SLine_0.20
(( +0.48113 0.27778j))
=SLine_0.25_b(( +0.50771 0.21067j)) =SLine_0.25
(( +0.3849 0.22222j))
The reactive power flow in line of 0.20j pu increases a little when comparing to the previous case (from 0.27 to 0.28pu). In contrast the real power flow reduces significantly from 0.48 pu to 0.35 pu.
The reactive power flow in line of 0.25j pu changes a little too when comparing to the previous case (from 0.22 to 0.21 pu) whereas the real power flow increases from 0.38 to 0.50 pu.
Therefore the regulating transformer with an increased phase angle will affect mostly the real power flow.

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 20 of 23
Problem 06.
6. Problem 3.60 in Glover, Sarma and Overbye
PowerWorld Simulator case Problem 3.60 duplicates Example 3.13 except that a resistance term of 0.06 per unit has been added to the transformer and 0.05 per unit to the transmission line. Since the system is no longer lossless, a field showing the real power losses has also been added to the one-line. With the LTC tap fixed at 1.05, plot the real power losses as the phase shift angle is varied from -10 to +10 degrees. What value of phase shift minimizes the system losses?.
≔θ
− °10
− °8
− °6
− °4
− °2
− °1
− °0.2
°0
°0.2
°1
°2
°4
°6
°8
°10
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
≔PLosses ⋅
24.917
22.002
19.711
18.049
17.016
16.736
16.626
16.614
16.609
16.65
16.843
17.703
19.192
21.309
24.051
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
≔QLosses ⋅
100.288
88.67
79.611
73.123
69.211
68.223
67.897
67.881
67.890
68.184
69.133
72.968
79.378
88.358
99.897
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
The system losses are minimized at near 0 degrees, P=16.609 MW and Q=67.89 MVAR

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 21 of 23
18.3
19.15
20
20.85
21.7
22.55
23.4
24.25
16.6
17.45
25.1
-6 -4 -2 0 2 4 6 8-10 -8 10
θ (( ))
PLosses(( ))
73.5
76.5
79.5
82.5
85.5
88.5
91.5
94.5
97.5
67.5
70.5
100.5
-6 -4 -2 0 2 4 6 8-10 -8 10
θ (( ))
QLosses(( ))

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 22 of 23
Problem 07.
6. Problem 3.61 in Glover, Sarma and Overbye
Repeat Problem 3.60, except keep the phase-shift angle fixed at 3.0 degrees, while varying the LTC tap between 0.9 and 1.1. What tap value minimizes the real power losses?
≔Tap
0.900
0.925
0.950
0.975
0.9875
1.000
1.0125
1.025
1.050
1.075
1.100
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
≔PLosses ⋅
19.578
18.241
17.320
16.785
16.652
16.604
16.638
16.750
17.194
17.914
18.885
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
≔QLosses ⋅
79.794
74.457
70.814
68.738
68.249
68.106
68.296
68.805
70.728
73.773
77.846
⎡⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎢⎣
⎤⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎥⎦
The system losses are minimized at TAP=1, P=16.604 MW and Q=68.106 MVAR

Session 21Fall 2013ECE421:
Introduction to Power SystemsHomework # 04
Due Session 21 (October 14th)Arturo Barradas Munoz Page 23 of 23
The system losses are minimized at near 0 degrees, P=16.609 MW and Q=67.89 MVAR
17.2
17.5
17.8
18.1
18.4
18.7
19
19.3
16.6
16.9
19.6
0.94 0.96 0.98 1 1.02 1.04 1.06 1.08 1.10.9 0.92 1.12
Tap
PLosses(( ))
70
71
72
73
74
75
76
77
78
79
68
69
80
0.94 0.96 0.98 1 1.02 1.04 1.06 1.08 1.10.9 0.92 1.12
Tap
QLosses(( ))