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EE 456 Design Project December 7, 2011

Project Members: Eurydice B Ulysses

Yanyi He

Ayoub Ali

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Table of Contents

Transmission Map……………………………………………………………………………………….3

One-Line Diagram……………………………………………………………………………………….4

Introduction ……………………………………………………………………………………………….5

Section 1 Base Case ………..........................................................................................................................................5

Base Case Bus Voltages and Angles.............................................................................................................6

Real and Reactive Power Flow at all Lines...................................................................................................6

Generator Real and Reactive Power Outputs ...............................................................................................7

Voltage Ratings Violation for Base Case......................................................................................................8

Contingency Analysis of the Base Case........................................................................................................8

Generator Outage Data...................................................................................................................................9

Full Contingency Assessment of Base case...................................................................................................9

Cost of Resolving Base Case Issues............................................................................................................10

Section 2

Modified Power System for New Needs…….. ...........................................................................................11

Normal Operating Conditions Voltage Ratings Violations….....................................................................11

Contingency Analysis of Modified Power System......................................................................................12

Generator Outage Data………………………….........................................................................................12

Full Contingency Assessment of the New Design………...........................................................................12

Cost of the New System……...………………............................................................................................14

Validation of Minimal Cost………………….............................................................................................14

Conclusion……..………………………………………………………………………………………….14

References……..………………………………………………………………………………………….15

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Transmission Map

Figure 1: A transmission map of the system with modifications showing the line routes and voltages

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One-Line Diagram

Figure 2: A one-line diagram of the system showing bus, line, transformer, and load connections

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Introduction

A power system is an energy system consisting of loads, supplies, transformers, transmission

lines, etc. The transmission lines provide paths from supplies to distanced loads. The

transformer is a facility to coordinate system operation at different voltage levels. The

coordination of all the proper power system infrastructures ensures reliable operations. A well-

designed power system is not vulnerable to rational changes of systems or even contingencies.

We call it a reliable power system. The reliability standards are referred to criteria of North

America Electric Reliability Corporation (NERC) [1].

In this project, we were initially given a reliable system. However, the system may not have been

reliable when considering NERC reliability criteria. Firstly, we proposed some investments and

upgrading strategies to modify the exercise system. Secondly, the system was subject to changes.

The changes partially contained load growth, additional infrastructures, and potential

contingency events. Our group aimed to find one of the most economic ways to modify the

previous reliable power system that was still valid under changes according to NERC standards.

The new power system could also satisfy and serve new needs. All the numerical results were

obtained from PSSE.

The report is organized as follows: Section 2 is introduction of our existing power system.

Section 3 is the primarily modified power system with additional infrastructures for load growth.

We will give our economic design in Section 4. Contingencies study is in Section 5.

Section 1

Base Case

The base case was composed of 10 real and reactive loads, 3 generators, 2 transformers, and 20

transmission lines located at 17 buses. Tables I to IV are data of loads, generators, transformers,

and transmission lines respectively. The tables also show the operation results of the base case.

We had 4 voltage violations of base case at buses 10, 13, 16, and 17 under normal conditions. All

4 violations were due to low voltage. Therefore, the most economical way to increase the voltage

was to install fixed shunt capacitors at the violating buses. The capacities of fixed shunt had to be

within a certain range. A small shunt would not be enough to cause any leverage, and a large

shunt would cost more and cause excessive voltage. The 4 violated buses were all 69 kV buses.

In order to avoid recurrent violation, we picked buses 10, 11, 13, and 16 to install the fixed

shunt. We noted that when bus 11 was not picked, it showed violation in contingency analysis

frequently. Although bus 17 was neglected in the selection, capacitors at bused 10, 13, and 16

helped balance the voltage output at bus 17. After careful consideration, 15 MVAR fixed shunts

were installed at buses 10, 11, and 13, and 5 MVAR was added to bus 16.

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Table I: Bus Voltages and Angles

Bus number Bus name Bus voltage (pu) Angle (degrees)

1 OWL 1.0 0

2 SWIFT 1.0 -1.58

3 PARROT 1.0 -3.08

4 LARK 0.9620 -6.57

5 JAY 0.9630 -6.79

6 RAVEN 0.9670 -6.76

7 WREN 0.9612 -7.15

8 ROBIN 0.9687 -6.32

9 SISKIN 0.9704 -4.22

10 JUNCO 0.9036 -10.02

11 QUAIL 0.9761 -4.60

12 HERON 0.9840 -4.19

13 EGRET 0.8955 -11.59

14 GULL 0.9926 -2.68

15 CROW 0.9691 -6.26

16 YANYI 0.9532 -7.92

17 EURY 0.9528 -6.39

Table II: Real and Reactive Power Flow and Currents at all Lines

From

Bus Name

To

Bus

Name

Real

Power

Flow

(MW)

Reactive

Power

Flow

(MVAR)

Current

(Amps)

1 Owl 9 Siskin 111.0 26.4 409

11 Quail 78.2 9.7 282

14 Gull 5.9 -1.2 21

2 Swift 11 Quail 89.6 24.3 333

12 Heron 81.2 13.9 295

14 Gull 29.2 4.2 106

3 Parrot 6 Raven 68.1 28.0 322

12 Heron 17.1 13.9 110

15 Crow 64.9 31.8 333

4 Lark 5 Jay 35.8 -7.6 55

9 Siskin -65.8 -2.4 271

5 Jay 4 Lark -12.7 6.5 53

6 Raven -4.3 -12.1 48

7 Wren 34.2 1.4 127

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8 Robin -27.2 -11.6 110

11 Quail -90.0 -14.3 340

6 Raven 3 Parrot -84.3 -25.7 327

5 Jay 4.3 10.7 43

7 Wren 5 Jay -34.2 -2.0 128

15 Crow -55.8 -18.0 219

8 Robin 5 Jay 27.2 10.4 108

12 Heron -67.2 -15.4 255

9 Siskin 1 Owl -109.4 -21.1 412

4 Lark 73.2 2.8 271

17 Siskin 26.2 13.3 109

10 Junco 13 Egret 10.6 .3 98

17 Siskin -25.6 -10.3 255

11 Quial 1 Owl -77.0 -8.7 285

2 Swift -88.7 -22.3 336

5 Jay 90.7 15.9 338

12 Heron 2 Swift -80.5 -13.0 297

3 Parrot -27.3 -17.3 118

8 Robin 67.7 15.3 253

13 Egret 10 Junco -10.5 -.3 98

16 Crow -19.5 -9.7 204

14 Gull 1 Owl -5.9 -2.8 23

2 Swift -29.1 -7.2 108

15 Crow 3 Parrot -86.1 -29.5 337

7 Wren 56.0 17.6 217

16 Crow 20.1 11.9 86

16 Crow 13 Egret 20.1 11.1 202

15 Crow -20.1 -11.1 202

17 Siskin 9 Siskin -26.2 -12.1 254

10 Junco 26.2 12.1 254

Table III: Generator Real and Reactive Power Outputs

Generator Name

Real

Power

Output

(MW)

Reactive

Power Output

(MVAR)

1 Owl 195.0274 34.9193

2 Swift 200 42.4533

3 Parrot 200 73.6848

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Table IV: Voltage Ratings Violation for Base Case on Line 5-11

Bus Number Bus name Bus Voltage Min Voltage Allowed Difference

Current

Violation

10 Junco 0.9036 0.96 0.054 No

13 Egret 0.8955 0.96 0.0645 No

16 Crow 0.9532 0.96 0.0068 No

17 Siskin 0.9528 0.96 0.0071 No

Under normal operations, the voltage stayed between 0.96 and 1.0 per unit. Under emergency,

the voltage was allowed to range from 0.90 to 1.05 per unit. The reactive generation capacity

was 490 MW, and the reactive generation capacity is from -100 MVAR to 250 MVAR. We

almost evenly distribute 1/3 of real power to each generator. P2 and P3 were set to 200 MW in

the baseline system.

From the results, we observed that the entire voltage amount stayed within the limits. Except bus

13, all other bus angles were below 10 degrees. The loss in the system was (200 + 200 + 194.3

585 =) 9.3 MW. The efficiency of the system was 98.4%. With regards to the current, the

currents were all below 50% of the rating. The system state could be considered to be close to

perfect.

Contingency Analysis of Base Case

We evaluated our system based on NERC criteria. Performance A is essentially our normal

operations, which was discussed above. Performance B is basically the N-1 contingency

analysis. We considered generator outage, transmission line outages, and transformer outages.

When we simulated generator outages, we almost evenly distribute the generation from the

outage generator to other generators in service.

Among all the contingencies, the only violation that was observed was under Line 2-14. When

Line 2-14 was taken off from the system, we could see the bus 14’s voltage would drop from

0.9926 to 0.8651 p.u. Generally, although the systems were under contingency simulation, the

system voltage was not dropped a lot. Most voltages were higher than 0.95 p.u. The currents

were within the rating. Moreover, it was counterintuitive to see that transmission line outages

would better off the system’s efficiencies. Because when we removed a line, we could avoid the

power loss in the removed one as well. The loads at 69 kV buses were rural loads and small,

thus transformer contingencies would not affect the whole system much as long as there was

one transformer to connect to generator to the load.

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Table V: Generator Outage Data for Base Case

Generator Outage Name Bus Number

Bus

Name Bus Voltage Difference

Current

Violation

1 Owl 13 Egret 0.8936 0.0033 No

2 Swift

10

13

Junco

Egret

0.8946

0.8863

0.0054

0.0137

No

3 Parrot

10

13

Junco

Egret

0.8656

0.8512

0.0244

0.0488

No

Table VI: Full Contingency Assessment for Base Case

From Bus

number

From bus

name

To bus

number

To bus

name

Voltage

Violation

Current

Violation

1 Owl 9 Siskin

Egret (0.8658)

Junko (0.8669) No

1 Owl 11 Quail

Junco(0.8968)

Egret (0.8893) No

1 Owl 14 Gull Egret (0.8955) No

2 Swift 11 Quail

Junco(0.8987)

Egret (0.8902) No

2 Swift 12 Heron Egret (0.8922) No

2 Swift 14 Gull

Egret (0.8958)

Gull (0.8656) No

3 Parrot 6 Raven

Junco (0.8947)

Egret (0.8860) No

3 Parrot 12 Heron Junco(0.8911) No

3 Parrot 15 Crow

Egret (0.8680)

Junko (0.8821) No

4 Lark 5 Jay Egret(0.8942) No

4 Lark 9 Siskin Egret(0.8956) No

5 Jay 6 Raven Egret(0.8932) No

5 Jay 7 Wren

Junco (0.8988)

No

5 Jay 8 Robin

Junco (0.8986) No

5 Jay 11 Quail

Junco (0.8855) No

7 Wren 15 Crow None No

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8 Robin 12 Heron

Egret (0.8895)

Junco (0.8979) No

10 Junco 13 Egret

Egret (0.8712)

No

10 Junco 17 Eury

Junco (0.6822)

Egret (0.7679) No

13 Egret 16 Yanyi

Junco (0.7809)

Egret (0.7211) No

Cost of Resolving Base Case Issues

We added fixed shunt at bus 14 to resolve the problem. However, under normal conditions, the

fixed shunt would cause excessive voltage. If we added a fixed shunt at bus 14 to avoid voltage

drop under contingency, we needed to add breaker to the shunt as well. The fixed shunt would

not be applied unless contingency happens.

Adding 4 Capacitor banks at the buses 4, 11, 13 and 16 resolved all these voltage violations and

satisfied the NERC criteria, and the capacities were 15, 15, 15 and 5 MVAR respectively.

We added 4 capacitor banks at the cost = 3000*50 = $0.150 million

Installation and associated equipment cost = 4*$60,000 = $0.240 million

Total cost = $0.39 million

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Section 2 Modified Power System for New Needs Figure 1 is the new power system network. We have additional load at additional bus 18. Two

new transmission lines connect bus 18 with bus 14 and bus 2. Although Line 2-18 is enough to

serve the steel mill under normal conditions, but considering the contingency of Line 2-18, it

would not serve the steel mill, therefore, we invested in two new lines connecting the steel mill.

In the new system, we also assumed that all the loads were increased by 30% without changing

the power factors. Similar to before, we almost evenly distributed the generation to 3 generators.

P2 and P3 were 270 MW.

Under normal conditions (after modification), the maximal current was from Line 4-9, 52% of

the rating. The voltages now were certainly with assigned ranges. However, the voltage angles

were not as small as the baseline case. Buses 10 and 13’s angles were around 14 degrees and 16

degrees respectively. The systems current efficiency was (585*1.3+40)/(270*2+278) = 97.8 %.

The efficiency decreased by 0.7 % compared to baseline system. This was due to additional

losses in the new line.

Table VIII: Normal Operating Conditions Voltage Ratings Violation

Bus

Number

Bus name Bus

Voltage

Min

Voltage

Allowed

Difference Current

Violation

4 Lark 0.9461 0.96 0.0139 No

5 Jay 0.9479 0.96 0.0121 No

6 Raven 0.9537 0.96 0.0063 No

7 Wren 0.9455 0.96 0.0145 No

8 'ROBIN' 0.9559 0.96 0.0041 No

9 'SISKIN' 0.9568 0.96 0.0032 No

10 'JUNKO' 0.8623 0.96 0.0977 No

13 'EGRET' 0.8515 0.96 0.1085 No

15 GROW 0.9561 0.96 0.0039 No

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Contingency Analysis of Modified Power System

When generator 1 or 3 was under outage, we could not simply assign half loads to the other 2

generators, because the currents would violate the rating. Thus, when generator 1 was under

outage, we re-dispatched the generation to be 373.53A and 450A for generators 1 and 3

respectively. When generator 3 was under outage, we re-dispatched the generation to be

347.5815A and 485A for generators 2 and 3 respectively. The line currents would come below

the rating limits again. However, we needed to add some costs of the re-dispatch since the local

marginal prices varied across locations.

Table IX: Generator Outage

Generator Outage Name Bus Number

Bus

Name Bus Voltage Difference

Current

Violation

1 Owl

10

13

Junko

Egret

0.8360

0.8288

0.0640

0.0712

No

2 Swift

10

13

Junco

Egret

0.8486

0.8366

0.0514

0.0634

No

3 Parrot

3

4

5

6

7

8

10

13

15

16

17

Parrot

Lark

Jay

Raven

Wren

Robin

Junko

Egret

Grow

Yanyi

Eury

0.8926

0.8922

0.8871

0.8781

0.8765

0.8975

0.7979

0.7776

0.8768

0.8539

0.8854

0.0674

0.0678

0.0729

0.0819

0.0835

0.0625

0.1621

0.1824

0.0832

0.1061

0.0746

No

Table X: Full Contingency Assessment of the New Design

From Bus

number

From bus

name

To bus

number

To bus

name Voltage Violation

Current

Violation

1 Owl 9 Siskin

Egret (0.8278)

Junco(0.8373) No

1 Owl 11 Quail

Egret (0.8514)

Junco(0.8623) No

1 Owl 14 Gull

Egret (0.8461)

Junco(0.8567) No

2 Swift 11 Quail

Egret (0.8434)

Junco(0.8550) No

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2 Swift 12 Heron

Egret (0.8461)

Junco (0.8567) No

2 Swift 14 Gull

Egret (0.8493)

Junco(0.8605) No

2 Swift 18 Steel Mill

Egret(0.8086)

Junco(0.8280)

Yanyi (.8818) No

3 Parrot 6 Raven

Egret (0.8492)

Junco (0.8589) No

3 Parrot 12 Heron

Egret(0.8493)

Junco(0.8638) No

3 Parrot 15 Crow

Egret (0.8453)

Junko (0.8610) No

4 Lark 5 Jay

Egret(0.8414)

Junco(0.8540) No

4 Lark 9 Siskin

Egret(0.8413)

Junco(0.8539) No

5 Jay 6 Raven

Egret(0.8213)

Junco(0.8322) No

5 Jay 7 Wren

Egret (0.8534)

Junco (0.8539)

Jay (.8977)

Wren (.8869) No

5 Jay 8 Robin

Egret (0.8578)

Junco (0.8606)

Wren (.8992) No

5 Jay 11 Quail

Egret (0.7998)

Junco (0.8785) No

7 Wren 15 Crow

Junco (0.8702)

Egret(0.8655) No

8 Robin 12 Heron

Junco (0.8533)

Egret(0.8419) No

10 Junco 13 Egret

Junco (0.8864)

Egret(0.8115) No

10 Junco 17 Eury

Junco( 0.4892)

Egret (0.5569)

Yanyi (0.8340 ) No)

13 Egret 16 Yanyi

Junco (0.6238)

Egret ( 0.5267 )

Eury ( 0.8337 ) No

14 Gull 18 Steel Mill

Junco(0.8622 )

Egret(0.8514 ) No

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Cost of the New System

Transmission Line 2-18: 161kV, line length 16.00 miles

Transmission Line 14-18: 161kV, line length 18.00 miles

Line breaker cost is $95,000 for one.

Cost per miles: 0.106 million $ / mile

Conductor: Dove

Fixed shunt: total shunt: 25+20+25+17=87 MVAR

Transmission Line 2-18: 161kV 34*0.106= 3.6040 million $

Transmission Line 14-18: 161kV

Line Breaker cost 0.38 million $

Fixed shunts at buses 4*0.06+0.003*87= 0.501 million $

Site cost 0.3 million $

Total Cost 4.785 million $

Validation of Minimal Cost

Process on searching the optimal investment decisions:

i) In order to serve the steel mill, we had to connect the steel mill to the system, but the

system had to be valid under contingency, hence we had to add at least two lines. Since

the cost was in positive correlation to the distance, we preferred a shorter line. Thus,

Line 2-18 and Line 14-18 were the best choice. Since bus 2 and 14 were both 161kV,

bus 18 was assigned to be 161kV as well, as otherwise we would have to pay additional

transformer cost.

ii) As for the transmission line conductor, the contingency analysis results told us that Dove

was enough to serve the system, which was the cheapest type at a 161 kV level.

iii) Under contingency analysis, voltage violation was our only concern, because there was

no current violation. The cheapest way we could choose to resolve voltage violation was

by adding fixed shunt capacitors. We recorded buses that violated the voltage limit.

Adding one shunt would cause voltage change on other buses as well. After

experimenting, we picked buses 4, 10, 13, and 16 and added 25, 20, 25 and 15 MVAR

fixed shunts.

Conclusion

We designed a new system to meet with load growth and new needs from a steel mill. After full

contingency analysis of the new system, we found solutions to help the system to meet the

NERC reliability standards by adding fixed shunts. Our solution was an approximate optimal

solution of cost minimization. The final system satisfied NERC performance A and B criteria.

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References

[1] North American Electric Reliability Corporation Standard TPL-001-0.1 – System

Performance under Normal Conditions