Transcript History of Power System - University of Washington

History of Power Systems
(c) M. A. El-Sharkawi, university of Washington
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Road to Power Systems
• Greek philosopher Thales of
Miletus (around 600 BC)
– When rubbing fur on amber,
electric charge is built up on the
amber.
– The charge attracts light objects
such as hair.
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Road to Power Systems
• English physician William
Gilbert (1544-1603)
– Was the first to use the term
electric
• Derivation from the Greek word for
amber (ηλεκτρον).
• The word amber itself was derived
from the Arabic word Anbar.
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Road to Power Systems
• Italian scientist Alessandro
Guiseppe Antonio Anastasio
Volta (1745-1827)
– Galvanism occurred whenever
moist is placed between two
different metals.
– The first battery was invented in
1800.
– Today we use the unit Volt for the
electric potential in honor of this
great Italian inventor.
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(c) M. A. El-Sharkawi, university of Washington
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Road to Power Systems
• French mathematician and
physicist André-Marie Ampère
(1775-1836).
– Explain the link between magnetism
and electric currents.
• The basis of electromagnetic devices:
motors, generators, transformers, etc.
– Today we use Ampere as a unit for
electric current in honor of this
French scientist.
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Road to Power Systems
• German scientist George
Simon Ohm (1789-1854)
– Related electric current to the
electromotive force.
– His work is known as Ohm's law.
– The theory opened the door wide
for circuit anaysis and designs.
– We now use Ohm as the unit for
resistance (or impedance) in his
honor.
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Road to Power Systems
• English chemist and
physicist Michael
Faraday (1791-1867).
– Developed the
foundations of all
electromechanical
theories.
– In his memory, the unit of
capacitance (farad) is
name after him.
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Road to Power Systems
• French instrument maker Hippolyte
Pixii (1808-1835)
– Not widely known inventor
– Built the first generator (or dynamo).
– His machine, named
magnetoelectric, was later developed
into the electrical generators.
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Pixii’s Generator
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Road to Power Systems
• Italian Antonio Pacinotti (18411912)
– 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.
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Stanley’s Transformer
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Road to Power Systems
• English Electrical Engineer and
Physicist John Ambrose Fleming
(1849-1945)
• invented the first electronic device
– two electrodes inside a vacuum tube. One
electrode was a heated filament (called
Cathode) that emitted electrons and the other
(called Anode) collected them
– This was the first vacuum tube diode
• Lee DeForest (American) later wrapped
a thin grid of wires around the cathode.
– By applying a small negative voltage to the
grid he managed to control the amount of
electrons reaching the Anode.
– This was the first vacuum tube amplifier
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Vacuum Tube
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Road to Power Systems
• The Ukranian Julius Edgar
Lilienfeld (1881-1963)
• Professor of Physics at the University of
Leipzig in Germany
• In 1926, he discovered the field effect
principals of the solid state material
• In 1947, Bell Laboratories physicists
Walter Houser Brattain (1902-1987),
John Bardeen (1908-1991), and William
Bradford Shockley (1910-1989)
developed the first practical bipolar
transistor based on Lilienfeld discovery
• These discoveries led the way to the
power electronics revolution
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Thomas Edison and Nicholai Tesla
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Thomas Edison
• Born on February 11, 1847, in Milan,
Ohio, and died on 1931 at age 84.
• Had 1093 patents.
– his first patent was granted at age 21
– his last one was at age 83.
– an average of about 1.5 patent per
month.
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Thomas Edison
• In 1874 at age 27, Edison opened his first research and
development laboratory in Newark, New Jersey.
• In 1876, he moved the facilities to Menlo Park, NJ
– The finest research and development laboratories in the world at
that time.
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Thomas Edison
• The electric light bulb is one of Edison’s most
important inventions (1878).
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Thomas Edison
• Edison received the U.S. congressional
gold medal for career achievements in
1928.
• When Edison died on 1931, people world
wide dimmed their lights in honor of his
man’s achievements.
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Nikola Tesla
• Nikola Tesla was born in Smiljan, Croatia
on July 9, 1856.
• During his career, Tesla had over 800
patents.
• Tesla moved from Europe to the United
States in 1884.
• He worked for Thomas Edison in his lab
as a research assistant.
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Tesla’s ac motor
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Nikola Tesla
• Tesla received the IEEE Edison Medal in 1917,
the most coveted electrical prize in the United
States.
• Tesla was inducted into the Inventor's Hall of
Fame in 1975.
• In 1956, the term "tesla" was adopted as the unit
of magnetic flux density in the MKSA system in
his honor.
• In 1975, the IEEE Power Engineering Society
established the Nikola Tesla Award in his honor.
• Tesla died on January 7, 1943.
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The Battle of ac versus dc
Voltage or Current
Voltage or Current
Time
Time
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The Battle of DC versus AC
• Edison system was 100V Direct
Current
• In September 1882, his Pearl
Street plant in lower Manhattan
starts operation
– the world's first commercial electric
lighting power station.
– City of Brockton, Massachusetts is
the first city to be electrified (1883).
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Problems With Low Voltage
• 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
• 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
Vload
VS
R
Load
Vload  VS  I Rwire
Vload
VS
I R
R
R  Rwire
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Rwire
Wire Resistance
: Resistivity of wire
l

A:cross section of wire
A
l: length of wire
• To reduce the wire resistance, A should
increase. 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
•
To have several small cross-section wires
feeding areas with high demands.
–
•
To place electrical generators at every
neighborhood.
–
•
Expensive solution; more wires for long miles.
Impractical and expensive solution.
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
• 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.
• However, adjusting the voltage of dc systems
was beyond the technology at that time.
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Tesla’s Solution
• Tesla was aware of the transformer invented by
Pacinotti
• The transformer can adjust the ac voltage, not
the dc
• Tesla proposed to rebuild the power system
based on ac technology
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Here Comes the AC!
• Main Advantage of AC:
– The voltage of AC systems can be changed
by transformers.
• 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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Tesla’s Solution (ac system)
Rwire
Source
I
VS
V1
Vload
V2
Transformer 1
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Transformer 2
R
Load
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Example
VS = 100 V, R = 1 , Rwire = 0.5 
Compute the following:
1. The voltage at the load side
2. The percentage of the load voltage with respect to the
source voltage
3. The energy consumed by the load during a 10 hour
period
4. The maximum load (minimum resistance) if the load
voltage cannot be reduced by less than 10% of the
source voltage.
5. The energy consumed by the new load during a 10 hour
period.
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Solution
Vload
Vs
100


 66.67 V
 Rwire 
 0.5 
1 
 1 

 1 
 R 
Vload
 66.67 %
Vs
2
Vload
66.67 2
EPt
t
10  44.444 kWh
R
1
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Solution
Vload

Vs
1
 Rwire 
1 

 R 
1
0 .9 
 0 .5 
1 

 R 
EPt
2
load
V
R

0.9* 100
t
2
4.5
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10  18.0 kWh
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Edison’s Reaction to Tesla’s Idea
• Edison was not impressed by Tesla’s AC
system because of its unsafe high voltage
wires that would pass through residential
areas.
• Most historians believe that Edison’s
rejection to the AC system was because
he had too much money invested in the
DC infrastructure.
(c) M. A. El-Sharkawi, university of Washington
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Edison’s Reaction to Tesla’s Idea
• Edison used unconventional methods to
convince the public that Tesla’s high voltage ac
system was too dangerous.
– Live demonstrations where he deliberately
electrocuted animals such as puppies, cats, horses
and even elephants.
– Edison went so far as to convince the state of New
York to use an electric chair powered by high voltage
ac system to execute condemned inmates on the
death row. Most historians believe that his real
motive was to further tarnish the safety of the ac
system.
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Edison high voltage test
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And the Winner is
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World at Night
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World Electric Energy Capacity
20,000
19,000
TWh=109 kWh
TWh
18,000
17,000
16,000
15,000
14,000
13,000
12,000
1994
1996
1998
2000
2002
2004
2006
Year
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