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ECE 476 POWER SYSTEM ANALYSIS. Lecture 1 Introduction Professor Tom Overbye Department of Electrical and Computer Engineering. About Me. Professional Received BSEE, MSEE, and Ph.D. all from University of Wisconsin at Madison (83, 88, 91)

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ece 476 power system analysis

ECE 476POWER SYSTEM ANALYSIS

Lecture 1

Introduction

Professor Tom Overbye

Department of Electrical andComputer Engineering

about me
About Me
  • Professional
    • Received BSEE, MSEE, and Ph.D. all from University of Wisconsin at Madison (83, 88, 91)
    • Worked for eight years as engineer for an electric utility (Madison Gas & Electric)
    • Have been at UI since 1991, doing teaching and doing research in the area of electric power systems
    • Developed commercial power system analysis package, known now as PowerWorld Simulator. This package has been sold to about 400 different corporate entities worldwide
    • DOE investigator for 8/14/2003 blackout
simple power system
Simple Power System
  • Every power system has three major components
    • generation: source of power, ideally with a specified voltage and frequency
    • load: consumes power; ideally with a constant resistive value
    • transmission system: transmits power; ideally as a perfect conductor
complications
Complications
  • No ideal voltage sources exist
  • Loads are seldom constant
  • Transmission system has resistance, inductance, capacitance and flow limitations
  • Simple system has no redundancy so power system will not work if any component fails
notation power
Notation - Power
  • Power: Instantaneous consumption of energy
  • Power Units

Watts = voltage x current for dc (W)

kW – 1 x 103 Watt

MW – 1 x 106 Watt

GW – 1 x 109 Watt

  • Installed U.S. generation capacity is about 900 GW ( about 3 kW per person)
  • Maximum load of Champaign/Urbana about 300 MW
notation energy
Notation - Energy
  • Energy: Integration of power over time; energy is what people really want from a power system
  • Energy Units

Joule = 1 Watt-second (J)

kWh – Kilowatthour (3.6 x 106 J)

Btu – 1055 J; 1 MBtu=0.292 MWh

  • U.S. electric energy consumption is about 3600 billion kWh (about 13,333 kWh per person, which means on average we each use 1.5 kW of power continuously)
power system examples
Power System Examples
  • Electric utility: can range from quite small, such as an island, to one covering half the continent
    • there are four major interconnected ac power systems in North American, each operating at 60 Hz ac; 50 Hz is used in some other countries.
  • Airplanes and Spaceships: reduction in weight is primary consideration; frequency is 400 Hz.
  • Ships and submarines
  • Automobiles: dc with 12 volts standard
  • Battery operated portable systems
electric systems in energy context
Electric Systems in Energy Context
  • Class focuses on electric power systems, but we first need to put the electric system in context of the total energy delivery system
  • Electricity is used primarily as a means for energy transportation
    • Use other sources of energy to create it, and it is usually converted into another form of energy when used
  • About 40% of US energy is transported in electric form
  • Concerns about need to reduce CO2 emissions and fossil fuel depletion are becoming main drivers for change in world energy infrastructure
sources of energy us
Sources of Energy - US

CO2 Emissions (millions of metric tons, and per quad)

Petroleum: 2598, 64.0 Natural Gas: 1198, 53.0Coal: 2115, 92.3

1 Quad = 293 billion kWh (actual)

1 Quad = 98 billion kWh (used, taking into account efficiency)

About 86% Fossil Fuels

In 2009 we got about 0.75% of our energy from wind and 0.04% from solar (PV andsolar thermal)

Source: EIA Energy Outlook 2011

global warming and the power grid what is known co2 in air is rising
Global Warming and the Power Grid, What is Known: CO2 in Air is Rising

Value wasabout 280ppm in 1800; in 2011 it is 394 ppm

Source: http://www.esrl.noaa.gov/gmd/ccgg/trends/

as has been worldwide temperature
As Has Been Worldwide Temperature

Baseline is 1961 to 1990 mean

Source: http://www.cru.uea.ac.uk/cru/info/warming/

change in u s annual average temperature
Change in U.S Annual Average Temperature

Source: http://www.isws.illinois.edu/atmos/statecli/Climate_change/ustrends.htm

but average temperatures are not increasing everywhere equally
But Average Temperatures are Not Increasing Everywhere Equally

Source: http://www.isws.illinois.edu/atmos/statecli/Climate_change/iltrends.htm

and where might temps go
And Where Might Temps Go?

The modelsshow rate of increase valuesof between0.15 to 0.4 C per decade.The rate from1975 to 2005was about 0.2 C per decade.

Source: http://www.epa.gov/climatechange/science/futuretc.html#projections

energy economics
Energy Economics
  • Electric generating technologies involve a tradeoff between fixed costs (costs to build them) and operating costs
    • Nuclear and solar high fixed costs, but low operating costs
    • Natural gas/oil have low fixed costs but high operating costs (dependent upon fuel prices)
    • Coal, wind, hydro are in between
  • Also the units capacity factor is important to determining ultimate cost of electricity
  • Potential carbon “tax” seen as unlikely soon
ball park energy costs
Ball park Energy Costs

Nuclear: $15/MWh

Coal: $22/MWh

Wind: $50/MWh

Hydro: varies but usually water constrained

Solar: $150 to 200/MWh

Natural Gas: 8 to 10 times fuel cost in $/MBtu

Note, to get price in cents/kWh take price in $/MWh and divide by 10.

natural gas prices 1990 s to 2011
Natural Gas Prices 1990’s to 2011

Marginal cost for natural gas fired electricity price

in $/MWh is about 7-10 times gas price

course syllabus
Course Syllabus
  • Introduction and review of phasors & three phase
  • Transmission line modeling
  • Per unit analysis and change of base
  • Models for transformers, generators, and loads
  • Power flow analysis and control
  • Economic system operation/restructuring
  • Short circuit analysis
  • Transient stability
  • System protection
  • Distribution systems
brief history of electric power
Brief History of Electric Power
  • Early 1880’s – Edison introduced Pearl Street dc system in Manhattan supplying 59 customers
  • 1884 – Sprague produces practical dc motor
  • 1885 – invention of transformer
  • Mid 1880’s – Westinghouse/Tesla introduce rival ac system
  • Late 1880’s – Tesla invents ac induction motor
  • 1893 – First 3 phase transmission line operating at 2.3 kV
history cont d
History, cont’d
  • 1896 – ac lines deliver electricity from hydro generation at Niagara Falls to Buffalo, 20 miles away
  • Early 1900’s – Private utilities supply all customers in area (city); recognized as a natural monopoly; states step in to begin regulation
  • By 1920’s – Large interstate holding companies control most electricity systems
history cont d24
History, cont’d
  • 1935 – Congress passes Public Utility Holding Company Act to establish national regulation, breaking up large interstate utilities (repealed 2005)
  • 1935/6 – Rural Electrification Act brought electricity to rural areas
  • 1930’s – Electric utilities established as vertical monopolies
vertical monopolies

Generation

Transmission

Distribution

Customer Service

Vertical Monopolies
  • Within a particular geographic market, the electric utility had an exclusive franchise

In return for this exclusive

franchise, the utility had the

obligation to serve all

existing and future customers

at rates determined jointly

by utility and regulators

It was a “cost plus” business

vertical monopolies26
Vertical Monopolies
  • Within its service territory each utility was the only game in town
  • Neighboring utilities functioned more as colleagues than competitors
  • Utilities gradually interconnected their systems so by 1970 transmission lines crisscrossed North America, with voltages up to 765 kV
  • Economies of scale keep resulted in decreasing rates, so most every one was happy
history cont d 1970 s
History, cont’d -- 1970’s
  • 1970’s brought inflation, increased fossil-fuel prices, calls for conservation and growing environmental concerns
  • Increasing rates replaced decreasing ones
  • As a result, U.S. Congress passed Public Utilities Regulator Policies Act (PURPA) in 1978, which mandated utilities must purchase power from independent generators located in their service territory (modified 2005)
  • PURPA introduced some competition
history cont d 1990 s 2000 s
History, cont’d – 1990’s & 2000’s
  • Major opening of industry to competition occurred as a result of National Energy Policy Act of 1992
  • This act mandated that utilities provide “nondiscriminatory” access to the high voltage transmission
  • Goal was to set up true competition in generation
  • Result over the last few years has been a dramatic restructuring of electric utility industry (for better or worse!)
  • Energy Bill 2005 repealed PUHCA; modified PURPA
utility restructuring
Utility Restructuring
  • Driven by significant regional variations in electric rates
  • Goal of competition is to reduce rates through the introduction of competition
  • Eventual goal is to allow consumers to choose their electricity supplier
the california enron effect

WA

ME

MT

VT

ND

MN

OR

NH

ID

SD

WI

NY

MA

WY

MI

RI

PA

CT

IA

NV

NE

NJ

OH

IN

DE

IL

UT

DC

W

VA

MD

CO

VA

KS

CA

MO

KY

NC

AZ

TN

OK

NM

AR

SC

GA

MS

AL

TX

LA

AK

FL

HI

electricity

restructuring

suspended

restructuring

delayed

restructuring

no activity

Source : http://www.eia.doe.gov/cneaf/electricity/chg_str/regmap.html

The California-Enron Effect
2007 illinois electricity crisis
2007 Illinois Electricity Crisis
  • Two main electric utilities in Illinois are ComEd and Ameren
  • Restructuring law had frozen electricity prices for ten years, with rate decreases for many.
  • Prices rose on January 1, 2007 as price freeze ended; price increases were especially high for electric heating customers who had previously enjoyed rates as low as 2.5 cents/kWh
  • 2009 average residential rate (in cents/kWh) is 9.08 in IL, 7.62 IN, 9.38 WI, 7.37 IA, 15.52 NY, 6.60 WA, 13.20 in CA, 9.82 US average
the rise of renewables
The Rise of Renewables

Currentlyabout 4%of our electric capacityis wind

The up/downsin 2001/2 and2003/4 werecaused by expiring tax

credits