Lecture 1Introduction to Power Systems

Dr. Ali Al-Awami

PowerPower: Instantaneous consumption of energy

Power Unit: Watt (W)

Installed Saudi generation capacity is about 50 GW (about 1.8 kW per person)

Maximum load of the Eastern Province of Saudi Arabia is about 12.5 GW

Energy

Energy: Integration of power over time; energy is what people really want from a power system

Saudi annual electric energy consumption is about 212 billion kWh (about 7,862 kWh per person, which means on average we each use 0.79 kW of power continuously)

Energy UnitsJoule = 1 Watt-second (J)kWh – Kilowatthour (3.6 x 106 J)

Power System Examples

Power grid: can range from quite small, such as an island, to one covering half the continent

– there are several major “interconnected” ac power systems in Saudi Arabia, each operating at 60 Hz ac. Many other countries, such as all other GCC countries, operate at 50 Hz.

Power System ExamplesSaudi Power Grid

Power System Examples

Airplanes and Spaceships: reduction in weight is primary consideration; frequency is 400 Hz.

Ships and submarines Electric vehiclesBattery operated portable systems

Sources of Energy - US

Source: EIA Energy Outlook 2011

CO2 Emissions (millions of metric tons)

Petroleum: 2598 Natural Gas: 1198Coal: 2115

About 86% Fossil Fuels

In 2009, US got about 0.75%

of its energy from wind and only 0.04% from solar (PV and solar thermal)

Global Warming and the Power Grid, What is Known: CO2 in Air is Rising

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

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

As Has Been Worldwide Temperature

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

Baseline is 1961 to 1990 mean

Electricity Market Models

• Vertical Monopoly: One company owns everything: generation, transmission, and distribution

• Deregulated Market: Several companies compete.

Vertical MonopoliesWithin a particular geographic market, the

electric utility had an exclusive franchise

Generation

Transmission

Distribution

Customer Service

In return for this exclusivefranchise, the utility had theobligation to serve all existing and future customersat rates determined jointlyby utility and regulators

It was a “cost plus” business

Utility Restructuring (Deregulation)Driven by significant regional variations in

electric rates (in some parts of the world, like the US and Europe)

Goal of restructuring is to reduce rates through the introduction of competition

Eventual goal is to allow consumers to choose their electricity supplier.

This is similar to the telecommunication market restructuring. Instead of a single service provider, multiple providers compete (STC, Mobily, Zain, etc.).

Power System History

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History

o William Gilbert, English (1544-1603)– Was the first to use the term electric

Derivation from the Greek word for amber. The word amber itself was derived from the

Arabic word عنبر.

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o Alessandro Volta, Italian (1745-1827)– Invented the first battery in 1800. – Today we use the unit Volt for the electric potential.

Historyo André-Marie Ampère, French (1775-1836)

– Understood the relation between electric currents and magnetism. Essential for motors, generators, and transformers.

– Ampere is used as a unit for electric current.

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o George Simon Ohm, German (1789-1854)– Related electric current to the electromotive force (Ohm's law). – The cornerstone for circuit analysis and designs. – Ohm is the unit for resistance.

History

o Michael Faraday, British (1791-1867)– His work set the foundations of all

electromechanical theories. – The unit of capacitance (farad) is named after

him.

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Historyo Antonio Pacinotti, Italian (1841-1912)

– invented a device that had two sets of windings wrapped around a common core.

– This was the basis for the transformers we use today. – Westinghouse further developed the transformer and

had several early models Gaulard and Gibbs transformer developed in 1883 Stanley transformer developed in 1886.

– Meanwhile, Ferranti was developing his own. This created fights over patenting!

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Ferranti’s Transformer

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Historyo John Hopkins, British– Patented the three-phase system for

generation and distribution in 1882

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Thomas Edison (1847-1931)

oAmericanoHad 1000+ patents! –his first patent was granted at age 21–his last one was at age 83. –What is Edison’s average patenting rate per

month?! – 1.5 patents/month!!– The most important of which is…

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Nikola Tesla (1856-1943)

o Serbiano 800 patents… only!!o Moved from Serbia to the US in 1884. o Worked for Edison in his lab as a research

assistant.o He left Edison’s lab after a salary dispute!

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AC vs. DC

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Should it be AC or DC?

o Edison system was 100V DCo In September 1882, his plant in New

York started operation– the world's first commercial electric

lighting power station.

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Problems With Low Voltage

o For the same power, the lower the voltage, the higher is the current.

P: PowerV: VoltageI: Current

IVP

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Problems With Low Voltage

o High currents require large cross section wires

– Expensive copper wires– Heavy wires that cannot be easily mounted on

transmission towers– Customers voltage is substantially reduced at heavy

loading conditions

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Line Voltage Drop

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Rwire

Load

Sour

ce

I

R VS Vload

RRR

VRIV

wire

Sload

Wire Resistance

A

lRwire

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o To reduce the wire resistance A should be increased. However, bigger cross section wires are– more expensive– heavier and would require poles to be placed at

shorter spans.

Edison’s Options

o To have several small cross-section wires feeding areas with high demands. – Expensive solution; more wires for long miles.

o To place electrical generators at every neighborhood. – Impractical and expensive solution. – Might be the choice of the future grid, though!

o To increase the voltage– Best solution, but the technology to increase the voltage

of the dc system was not available then.

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Tesla’s Solution

IVP

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o Tesla knew the problem was related to the low voltage (100 V) Edison was using in his dc system. – For same power, increasing the supply voltage reduces the

current.– Hence the voltage drop across the wire could be reduced.

o However, adjusting the voltage of dc systems was beyond the technology at that time.

Here Comes the AC!

o Main Advantage of AC:– The voltage of AC systems can be changed by

transformers.

o How about DC?– The transformers cannot change the DC voltage.

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Power plant Transformer 1

Transmission line

Low Voltage Transformer 2

Low Voltage

High Voltage

Tesla’s Solution (AC system)

So, who won the debate?

Tesla did32