lecture ee333 - lecture 1lwu/ee333/lectures... · gain an understanding of the power system, future...

Lecture 1

Introduction

Dr. Lei Wu

Department of Electrical and Computer Engineering

Clarkson University

EE 333

POWER SYSTEMS ENGINEERING

About The Class

� Course meeting time:

� TuTh 2:30pm-3:45pm CAMP 178

� Course website:

� http://people.clarkson.edu/~lwu/ee333/

� Office hours:

� Tu/Th 9:30-11:30am or by appointment

� Office: CAMP 147

� Phone: 315-268-3914

� E-mail: [email protected]

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About The Class (Cont’d)

� Textbook: J.D. Glover, M.S. Sarma, and T. Overbye, Power

System Analysis and Design, Fourth/Fifth Edition, Cengage

Learning.

� References:

� A.R. Bergen and V. Vittal, Power System Analysis, Second

Edition, Prentice Hall, 2000.

� Distributed notes and/or papers.

3

Homework

� For homework submission, staple all the pages and write yourname and student ID on the first page.

� Homework is due before the class on the due date.

� Late homework will not be accpted.

4

Exams

� Students are expected to attend all exams. If you find you must

miss an exam due to a legitimate conflict, a make-up will be

given only under the following conditions:

� The student has informed the instructor of the absence at least 24

hours in advance of missing the exam.

� The student misses the exam due to some situation beyond the student’s control (such as a serious illness, the family emergency, etc.),

which is unexpected, unavoidable, and documented. The reason for

each absence of this sort will be judged case by case by the instructor

and, if it is deemed valid under the above description, a make-up exam

will be given.

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Grading

� Grading:

� Homework: 5%

� In-class quizzes (exact homework questions): 25%

� Hour Exam: 30%

� Final Exam: 35%

� Class Attendance: 5%

� Bonus:

� Identify errors and suggest corrections

� Suggest improvements

� Design problems

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Topics Covered

� Gain an understanding of the power system, future trends, and

needs.

� Establish an understanding of real and reactive power flow,

power factor correction on a per phase basis with extension of

concepts to three phase circuits (Chapters 2-3)

� Model transformers and transmission lines at an appropriate

level to permit calculations under various load conditions

(Chapters 4-5)

� Introduce students to the study of load flow and gain an

understanding of iterative solution techniques leading to the use

of computer simulation methods (Chapter 6)

� Understand the sequence component technique and perform it

for system fault analysis. (Chapters 8-9)7

Topics Covered

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G1 G3

G2

T1

T2

T3 T4

T5 1

2

3

4

5

6

7 8

L1 L2

L3

Outline

� Notation (power, energy)

� Power system components

� Power system voltage structure

� Power system frequency

� Single phase and three-phase

� Evolution of the U.S. power industry

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Power: Instantaneous consumption of energy

Installed U.S. generation capacity is about 900 GW ( about 3 kW per person)

Maximum load of Clarkson Campus about 2 MW

Power Units Watts = voltage x current for dc (W)

kW – 1 x 103 Watt

MW – 1 x 106 Watt

GW – 1 x 109 Watt

Energy: Integration of power over time, is what people want from power systems

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)

Energy Units

Joule = 1 Watt-second (J)

kWh – Kilowatthour (3.6 x 106 J)

Btu – 1055.06 J; 1 MBtu=0.292 MWh

(British thermal unit)

Notation - Power and Energy

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Power System Overview

11

North American Electric Reliability Corporation

Interconnections

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Power System Components

� Generation

� Source of power, generators

� Transmission, subtransmission

� Transmits power, transmission network, transformers

� Distribution

� Distributes power, distribution network, transformers

� Load

� Consumes power

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Generation Mix (U.S.)

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Power System Voltage Structure

� Low voltage

� 120V, 208V, 140V, 480V, 600V

� Medium voltage

� 2.4kV, 4.16kV, 4.8kV, 6.9kV, 12.47kV, 13.2kV, 13.8kV, 23kV, 24.94kV, 34.5kV, 46kV, 69kV

� High voltage

� 115kV, 138kV, 161kV, 230kV

� Extra high voltage (EHV)

� 345kV, 500kV, 765kV

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Consumers

� Industrial sites: manufacturing, construction, mining, agriculture,

fishing and forestry establishments

� Commercial sites: non-manufacturing businesses (hotels,

motels, restaurants, wholesale, retail, health, social, educational)

� Residential sites: private households, residential buildings

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Goals of Power System Operation

� Supply load with electricity at

� specified voltage

� specified frequency

� with minimum cost

� Complications

� No ideal voltage sources exit

� Loads are constantly changing

� Transmission & distribution system has resistance, inductance, capacitance and flow limitations

� Power system is subject to disturbances, such as lightning strikes. Thus, simple systems without redundancy will not work if any component fails

� Engineering tradeoffs between reliability and cost

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Questions

� DC vs. AC

� 50Hz vs. 60Hz

� Single-phase vs. three-phase

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DC vs. AC

� DC

� High loads of direct current could rarely be transmitted for

distances of greater than one mile without introducing excessive

voltage drops.

� Direct current could not easily be changed to higher or lower

voltages.

� AC

� High voltage AC could be transmitted over long distances with

lower voltage drops (thus greater transmission efficiency), and

then conveniently stepped down to low voltages for use in

homes and factories.

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50Hz vs. 60Hz

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50Hz vs. 60Hz

� Each has advantages and disadvantages, and on balance it likely makes no real difference.� 50Hz

� Smaller reactance: lower reactive voltage drops and higher transmission capacity.

� Less line reactive charging.

� 60Hz

� The equipment (generator, transformer) is generally smaller with the same rating.

� Higher eddy and hysterisis losses increase with frequency (skin effect)

� For cables capacitive leakage becomes an issue for higher frequency.

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Single-Phase vs. Three-Phase

� Advantages of three-phase over single-phase� Reduced capital and operating costs of transmission and

distribution, as well as better voltage regulation

� The balanced three-phase system, while delivering the same power, requires only half the number of conductors needed for the three separate single-phase systems.

� The total I2R losses in the three-phase system are only half those of three separate single-phase systems.

� Line-voltage drop (IR) between the source and load in the three-phase system is half that of each single-phase system.

� In a balanced three-phase system, instantaneous power delivered to the external load is constant rather than pulsating as it is in a single-phase system.

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Evolution of the U.S. Power Industry

� Early 1880’s – Edison introduces 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

� 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

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� 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

� 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 Regulatory 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

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� 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

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Restructuring: What & Why

� What is Restructuring � Unbundling electric utilities from vertically-integrated monopolies

into separate generation, transmission and distributionentities.

� Let market forces drive the price of electric supply.

� Reduce the net cost through increased competition.

� Goal� Reduce energy charges through a competitive market.

� More customer choice by creating an open access environment that will allow consumers to choose a provider for electric energy.

� Level of service reliability can be priced for customers.

� More business opportunities for selling new products and services.

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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

Customers

Tie-Lines Tie-Lines

Transmission

Ge neration

Dis tribution

Vertically Integrate d Utility

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Vertical Monopolies

� It was a “cost plus” business� Identifying allowed costs and investments

� Setting an allowed rate of return so that the utility will have the appropriate level of earnings on its investment

� Required revenues (per MWh) remain fixed for certain periods.

� This provides an incentive for the utility to reduce cost. The utility earns higher rates of return by incurring lower costs than the costs anticipated

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Restructured Power Industry

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� Power Flow vs. Money Flow

Money Flow

Power Flow

GENCO

TRANSCO

DISCO

Marketer

Retailer

Aggregator

Broker

Customer

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Electricity Market National Overview

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Average Electricity Retail Price

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August 14th, 2003 Blackout

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Smart Grid

� The smart grid calls for the evolution to a 21st century power grid

that connects everyone to clean, abundant, affordable, and reliable

electricity anytime, anywhere. The smart grid will integrate

advanced techniques, including all kinds of generation sources,

customer participation, storage devices, and distributed intelligent

controllers, into electric grid. � Accommodates all generation and storage options

� Enables active participation by consumers

� Enables new products, services, and markets

� Operates resiliently against physical and cyber attacks, and natural disasters

� ……

� [DOE08a] U.S. Department of Energy, “The smart grid: an introduction,”

Available online at http://www.oe.energy.gov /DocumentsandMedia/

DOE_SG_Book_Single_Pages(1).pdf, 2008.35

Smart Grid - Consumer Opportunities

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EfficientBuildingSystems

UtilityCommunications

DynamicSystemsControl

DataManagement

DistributionOperations

DistributedGeneration& Storage

Plug-In Hybrids

SmartEnd-UseDevices

ControlInterface

AdvancedMetering

Consumer Portal& Building EMS

Internet Renewables

PV

Energy efficiency and demand response is a driver that will greatly accelerate the creation of a smart grid

Customer Involvement

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Concept of Microgrid

� Microgrids are small-scale, LV networks designed to supply

electrical and heat loads for a small community.

� Microsources are equipped with power electronic interfaces

(PEIs) and controls to provide the required flexibility as a single

aggregated system with specified power quality and output.

� Differences between microgrids and conventional power plants:

� Microsources are of much smaller capacity.

� Microsources at distribution voltage can be directly fed to the

utility distribution network.

� Microsources are normally installed close to customer premises

so that electrical/heat loads can be efficiently supplied with

satisfactory voltage and frequency profiles and negligible line

losses.

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Microgrid Integration

� Microgrid objectives are to improved reliability, self-healing,

distributed control.

� Microgrid is modular with small capacity that is geographically

dispersed and located near the load points. Physical proximity can

also reduce the transmission and distribution losses.

� Microgrid utilizes non-conventional/renewable energy resources

which will reduce fossil fuel usage.

� Microgrid reduces environmental pollution and global warming.

� Microgrid includes cogeneration plants that utilize wasted heat to

increase the overall energy efficiency.

� Microgrid can be interconnected in semi-autonomous power

systems or connected to utility distribution network.

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Concept of Microgrid

Microgrid

Distribution Switchyard

Transmission Sub-TransmissionHV SwitchyardGeneraion

Microgrid Structures

� Home Microgrid

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� Community Microgrid Structure

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� Corporate Building Microgrid

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