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DEPARTMENT OFELECTRICAL POWER ENGINEERING

POWER SYSTEMS IV(PSYS401)

PRACTICAL ASSIGNMENT

POWER SYSTEMS ANALYSIS (POWER FLOW)

10/16/2013LecturerMr. John Wimbush

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TABLE OF CONTENTS

1-INTRODUCTION..............................................................................................................................1

1.1-OBJECTIVES.............................................................................................................................1

2-GAUSS-SEIDEL METHOD..............................................................................................................2

2.1-MANUALLY CALCULATION USING GAUSS-SEIDEL METHOD......................................2

2.1.1- Y-BUS MATRIX CALCULATIONS.................................................................................2

2.1.2- BUS BAR-3 PHASOR VALUES CALCULATION USING GAUSS-SEIDEL METHOD (TWO ITERATIONS)...................................................................................................................3

3- POWER WORLD SIMULATION....................................................................................................5

3.1-SIMULATION RESULTS..........................................................................................................5

3.2- ANALYSING A POWER SYSTEM USING POWER WORLD SIMULATOR......................6

3.3- POWER SYSTEM ANALYSIS.................................................................................................8

3.3.1- POWER & POWER FACTOR SUPPLIED BY EACH GENERATOR.............................8

3.3.2- BUS-BARS VOLTAGES RESULT (S/S1-S4)...................................................................9

3.3.3- VALUE OF SHUNT REQUIRED ON BUSBARS SUB-BUS 1&2...................................9

3.3.4- TRANSFORMER-4 DISCONNETED FROM THE SYSTEM WHILE SHUNT CAPACITANCE IS ONLINE.......................................................................................................9

3.3.5- LINE BETWEEN FEEDER-2 AND POWER STATION-2 TRIPPED...............................9

3.3.6- SYSTEM TO BLACK-OUT...............................................................................................9

4- CONCLUSION AND RECOMMENDATIONS.............................................................................10

5- REFERENCES................................................................................................................................10

6-APPENDIX (a)................................................................................................................................11

6.1- SCENARIO-1 (SHUNT VALUE INCERTED INTO SUB-BUS1 & SUB-BUS2)..................11

6.2- SCENARIO-2 (TRANSFORMER T4 OUT OF SERVICE)....................................................12

6.3- SCENARIO-3 LINE BETWEEN FEEDER2 & POWER STATION 2 FAULTED.................13

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LIST OF FIGURES

Figure 2.1: Gauss-Seidel Single Line Diagram..........................................................................2Figure 3.1: Power World Single Line Model.............................................................................5Figure 3.2: Main Single Line System Model.............................................................................8

LIST OF TABLES

Table 3.1: Voltage Magnitude and Angles................................................................................5Table 3.2: Line Flow and Line Losses.......................................................................................5Table 3.3: Real and Reactive Power Supplied by Bus Bars......................................................6Table 3.4: Ybus Matrix..............................................................................................................6Table 3.5: Line Data...................................................................................................................7Table 3.6: Bus bar Data..............................................................................................................7Table 3.7: Equipment Data........................................................................................................7Table 3.8: Generator Record Data.............................................................................................8Table 3.9: Bus bar Record Data.................................................................................................9

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1-INTRODUCTION

The load flow and voltage drop studies give the range of actual voltages that can appear at the load equipment terminals so as to confirm that the running voltages always stays within the range permitted for each equipment.

This report gives details of comparison between Gauss-Seidel method manually calculating the phase values (magnitude and angles) and using computer software (Power World) version 17.

In addition to that, the report also gives details on performing some power flow analysis on different single line diagrams by simulating in different scenarios.

1.1-OBJECTIVES

Simulate a simple power transmission system using a computer software package (Power World Simulator 17)

Performing some Power Systems analysis

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2-GAUSS-SEIDEL METHOD

2.1-MANUALLY CALCULATION USING GAUSS-SEIDEL METHOD

Figure 2.1: Gauss-Seidel Single Line Diagram

This picture shows the one-line diagram of a simple three-bus bar power system with generators at buses 1&3. The voltages, and load values are given. Line impedances are on 100MVA base. The voltage is 132KV; the resistance and capacitance of the line are neglected.

2.1.1- Y-BUS MATRIX CALCULATIONS

y12=1

jx12 =

1j 0.025

= -j40; y13=1

jx13 =

1j 0.05

= -j20; y23=1

jx23 =

1j 0.028

= -j35.71

Now let’s get the Y-bus matrix coefficients:

Y11 = y12 + y13 = -j40-j20 = -j60; Y22 = y12 + y23 = -j40-j32.71 = -j75.71;

Y33 = y13+y23 = -j20-j35.71 = -j55.71 Y12=Y21=- y12 = j40, Y13=Y31= - y13 = j20

Y23=Y32= - y23 = j35.71

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Y-BUS MATRIX

YBUS= [− j 60 j 40 j 20j 40 − j75.71 j 35.71j 20 j35.71 − j 55.71]

2.1.2- BUS BAR-3 PHASOR VALUES CALCULATION USING GAUSS-SEIDEL METHOD (TWO ITERATIONS)

The estimate initial values are: V3 (0) = 0.950 pu ; V1

(0) = 1.0250 pu; V2(0) = 10 pu

Let’s first convert all the power in per unit values:

P3 = 300100

= 3pu; P2 = 450100

= 4.5pu; Q2 = = 250100

= 2.5pu

The net-injected power in per unit at bus-bar 2 will be:

P2 = Pg2-PL2 = 0 - 4.5 = -4.5pu; Q2 = Qg2 - QL2 = 0 - 2.5 = -2.5pu

As Bus3 is a voltage control bus (PV bus), we have to calculate the Q3 first:

Q3 = -Im *[(Y33×V3 + Y31×V1+ Y32×V2) ×V3*]

Q3 = -Im *{0.950× [(55.710.9590×0.950) + (2090×1.0250) + (35.7190×10)]

Q3 = -Im *[3.1290] = 3.12-90 = -j3.12 pu

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Now we can start solving the iterations at Bus2&3, using the following formulas:

V2 (k+1) =

1Y 22

×[ P2− jQ 2

(V 2k )

−Y 21×V 1−Y 23×V 3k]

V3 (k+1) =

1Y 33

×[ P3− j Q3

(V 3k )

−Y 31×V 1−Y 32×V 2k +1]

For k=0

V2 (1) =

1− j 75.71

×[−4.5+ j 2.51 0

−40 90 ×1.025 0−35.71 90 × 0.950]V2

(1) = 0.958-3.55 pu

V3 (1) =

1− j 55.71

×[ 3+ j3.120.95 0

−20 90 × 1.025 0−35.71 90 ×0.958−3.55]V3

(1) = 0.9221.2 pu

For k=1

V2 (2) =

1− j 75.71

×[ −4.5+ j 2.50.958−3.55

−40 90× 1.025 0−35.71 90 × 0.9221.2] V2

(2) = 0.947-3.344 pu

V3 (2) =

1− j 55.71

×[ 3+ j3.120.922 1.2

−20 90 ×1.025 0−35.71 90× 0.947−3.344]V3

(2) = 0.91471.52 pu

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3- POWER WORLD SIMULATION

Using the information data from the figure 2.1 above the model below has been built in Power World simulator.

Figure 3.1: Power World Single Line Model

3.1-SIMULATION RESULTS

Table 3.1: Voltage Magnitude and Angles

Bus RecordsNumber Name

Nom kV

PU Volt

Volt (kV)

Angle (Deg)

1 Bus-1 132 1 132 02 Bus-2 132 0.9637 127.218 -2.91

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3 Bus-3 1320.9999

9 131.999 1.32

Table 3.2: Line Flow and Line Losses

Line RecordsFrom Number

From Name

To Number

To Name

Branch Device Type

MW From

Mvar From

MVA From

MW Loss

Mvar Loss

1 Bus-1 2 Bus-2 Line 195.9 149.9 246.7 0 15.221 Bus-1 3 Bus-3 Line -46 0.5 46 0 1.063 Bus-3 2 Bus-2 Line 254 138.7 289.4 0 23.45

Table 3.3: Real and Reactive Power Supplied by Bus Bars

Generators RecordsNumber of Bus

Name of Bus

Gen MW

Gen Mvar AGC AVR

Min MW

Max MW

Min Mvar Max Mvar

1 Bus-1 149.95 150.44 YES YES 0 1000 -9900 99003 Bus-3 300 139.24 YES YES 0 1000 -9900 9900

Table 3.4: Ybus Matrix

3.2- ANALYSING A POWER SYSTEM USING POWER WORLD SIMULATOR

It consists of a power station with two generators (Gen 1 & 2) which generate at 11KV. They feed two 132KV lines through two transformers. At the far end of the line is a substation with incoming EHV, (PwrSta 1 & 2). These are each connected to a transformer which steps the voltage down to HV of 33KV. There are HV bus bars in the substation with a bus-section between them. These bus bars feed a ring of four 33KV substations; each having loads as indicated in the data sheets below.

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Table 3.5: Line Data

Table 3.6: Bus bar Data

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Table 3.7: Equipment Data

Figure 2.2: Main Single Line System Model

3.3- POWER SYSTEM ANALYSIS

3.3.1- POWER & POWER FACTOR SUPPLIED BY EACH GENERATOR

Based on the simulation result shown in table8 below, it can be seen that the generators are equally shared.

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Table 3.8: Generator Record Data

Gen Records

Number of Bus

Name of Bus Status

Gen MW

Gen Mvar AVR

Min MW

Max MW

Min Mvar

Max Mvar

Power factor

1 Gen1 Closed 63.92109.7

2 YES 55 1000 -9900 9900 0.503

2 Gen2 Closed 70109.7

1 YES 55 1000 -9900 9900 0.505

3. 3.2- BUS-BARS VOLTAGES RESULT (S/S1-S4)

The table9 below shows the bus bars voltages of each bus load, and it can be seen that the voltage drop in each bus bar are not acceptable because they are all below minimum voltage drop variation (+/-5%) as stipulated by some companies or national/international standards.

Table 3.9: Bus bar Record Data

Bus Records

Number NameNom kV

PU Volt

Volt (kV)

Angle (Deg)

9 S/S1 33 0.71545 23.61 -15.4310 S/S2 33 0.65733 21.692 -20.2711 S/S3 33 0.65057 21.469 -20.9212 S/S4 33 0.72009 23.763 -14.88

3.3.3- VALUE OF SHUNT REQUIRED ON BUSBARS SUB-BUS 1&2

In order to pick the voltages on all bus bars within the minimum variation (+/-5%) a shunt of 90MVAr has been selected. See appendix (a) scenario-1

3.3.4- TRANSFORMER-4 DISCONNETED FROM THE SYSTEM WHILE SHUNT CAPACITANCE IS ONLINE

With transformer-4 going out for repair, the voltages level on load bus bars (S/S1-4) is still acceptable. See appendix (a) scenario-2

3.3.5- LINE BETWEEN FEEDER-2 AND POWER STATION-2 TRIPPED

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The line between feeder 2 and power station 2 has tripped due to a fault, the load bus bars are not badly affected because the voltage level remains within standards see appendix (a) scenario-3

3.3.6- SYSTEM TO BLACK-OUT

A black-out in the whole system should be in case of loss of the two main generators group.

4- CONCLUSION AND RECOMMENDATIONS

The manually calculation using Gauss-Seidel method to determine the Ybus matrix as well as the phase values (magnitude and angle) has not differed from the ones using the power world simulator.

In order to keep the voltages levels on bus bars (load bus bars) within the permitted voltage variation range a shunt value of at least 85-90MVAr should be used.

5- REFERENCES

[1] GUPTA, B. R. D. 1998. Power system analysis and design, New Delhi, Wheeler.

[2] GLOVER, J. D., SARMA, M. S. & OVERBYE, T. J. 2012. Power system analysis and design, Stamford, CT, Cengage Learning.

[3] GRAINGER, J. J. & STEVENSON, W. D. 1994. Power system analysis, New York, McGraw-Hill.

[4] BERGEN, A. R. & VITTAL, V. 2000. Power system analysis, Upper Saddle River, N.J, Prentice Hall.

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6-APPENDIX (a)

6.1- SCENARIO-1 (SHUNT VALUE INCERTED INTO SUB-BUS1 & SUB-BUS2)

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6.2- SCENARIO-2 (TRANSFORMER T4 OUT OF SERVICE)

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6.3- SCENARIO-3 LINE BETWEEN FEEDER2 & POWER STATION 2 FAULTED

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