Transcript m5zn_1ccd8e73e781118

Lecture 1
Introduction to Power Systems
Dr. Ali Al-Awami
Power
Power: 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 Units
Joule =
kWh –
1 Watt-second (J)
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 Examples
Saudi Power Grid
Power System Examples
Airplanes and Spaceships: reduction in weight
is primary consideration; frequency is 400 Hz.
Ships and submarines
Electric vehicles
Battery operated portable systems
Sources of Energy - US
CO2 Emissions (millions of metric
tons)
Petroleum:
2598
Natural Gas: 1198
Coal:
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)
Source: EIA Energy Outlook 2011
Global Warming and the Power Grid,
What is Known: CO2 in Air is Rising
Value was
about 280
ppm in
1800; in
2011 it is
394 ppm
Source: http://www.esrl.noaa.gov/gmd/ccgg/trends/
As Has Been Worldwide Temperature
Baseline is 1961 to 1990 mean
Source: http://www.cru.uea.ac.uk/cru/info/warming/
Electricity Market Models
• Vertical Monopoly: One company owns
everything: generation, transmission, and
distribution
• Deregulated Market: Several companies
compete.
Vertical Monopolies
Within a particular geographic market, the
electric utility had an exclusive franchise
Distribution
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
Customer Service
It was a “cost plus” business
Generation
Transmission
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
.
‫عنرب‬
o Alessandro Volta, Italian (1745-1827)
– Invented the first battery in 1800.
– Today we use the unit Volt for the electric potential.
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History
o 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.
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.
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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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History
o 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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History
o John Hopkins, British
– Patented the three-phase system for
generation and distribution in 1882
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Thomas Edison (1847-1931)
o American
o Had 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 Serbian
o 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 DC
o 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 V I
P: Power
V: Voltage
I: Current
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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
Rwire
Source
I
VS
Vload
R
Load
Vload
VS
I R
R
R  Rwire
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Wire Resistance
l
Rwire  
A
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.
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Edison’s Options
o
To have several small cross-section wires feeding
areas with high demands.
–
o
To place electrical generators at every
neighborhood.
–
–
o
Expensive solution; more wires for long miles.
Impractical and expensive solution.
Might be the choice of the future grid, though!
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
P V I
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.
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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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Tesla’s Solution (AC system)
Low Voltage
High Voltage
Transformer 2
Transmission line
Power plant
Transformer 1
Low Voltage
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So, who won the debate?
Tesla did
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