Download References History Summary Edison and Westinghouse The Grid

9/6/2016
References
• Basic physics - http://www.physicsclassroom.com/
• Electric circuits - http://hyperphysics.phyastr.gsu.edu/hbase/electric/ecircon.html
• Textbook -
Module -01
Industry Overview
Community College of Rhode Island
9/6/2016
Community College of Rhode Island
1
History Summary
9/6/2016
2
Edison and Westinghouse
• Benjamin Franklin Born in 1706
– 1752 kite experiment
• 1879, Thomas Edison invents a more efficient light
bulb
• 1882, Edison puts in operation the Pearl Street Plant
• Between 1750 and 1850 electricity and magnetism is
explored by
–
–
–
–
–
Volta
Coulomb
Gauss
Henry
Faraday
– first direct current (dc) distribution system
– New York City, powering over 10,000 electric light bulbs
• George Westinghouse developed a device called the
“transformer.”
• Inventions
–
–
–
–
–
–
battery (1800),
generator (1831),
electric motor (1831)
telegraph (1837
telephone (1876)
light bulb (1879)
Community College of Rhode Island
– The transformer allowed electrical energy to be transported over long
distances efficiently
9/6/2016
3
Community College of Rhode Island
9/6/2016
4
Simplified Electric Power System
Generation-Transmission-Distribution
The Grid – Edison-Westinghouse-Tesla
• Edison –DC grid
• Westinghouse – AC grid
• Tesla – Components for the AC
grid
• Worlds largest network
• The most important achievement
of the twenty century.
• Mostly one-way communications
Community College of Rhode Island
9/6/2016
5
Community College of Rhode Island
9/6/2016
6
1
9/6/2016
Voltage
Current
• Voltage is the potential energy source in an electrical
circuit that makes things happen(Electromotive Force or EMF)
• EMF unit is the volt
• Current is the flow of electrons in a conductor (wire).
• Electrons are pushed and pulled by voltage through
an electrical circuit or closed-loop path.
• The electrons flowing in a conductor always return to
their voltage source.
• Current is measured in amperes, usually called amps
• One amp is equal to 628 × 1016 electrons flowing in
the conductor per second
• Voltage tries to push or pull current
• When there is a complete circuit, voltage will cause
current to flow
– The volt was named in honor of Allessandro Giuseppe Antonio
Anastasio Volta (1745–1827), the Italian physicist who also invented
the battery.
• Electrical voltage symbol “e” or “E.”
– (Some references use symbols “v” or “V.”)
• Voltage is either direct or alternating
• Electric power systems are based on alternating
voltage applications
– from low-voltage 120 volt residential systems
– to ultra high voltage 765,000 volt transmission systems
Community College of Rhode Island
9/6/2016
7
Community College of Rhode Island
Power
9/6/2016
• Electrical energy is the product of electrical power
and time.
• Electrical energy is watt-hours (Wh)
• Common units of energy is kilowatt-hours –kWh
– ( 1,000 watt-hours) for residential applications
– Your electric bill is payment for energy
• Large energy applications is megawatt-hours-MWh
– (meaning 1,000,000 watt-hours) for industrial and utility companies
9
Community College of Rhode Island
dc Voltage ac Voltage and Current
9/6/2016
10
Frequency
• Direct current (dc) is the flow of
electrons in a circuit that is always in
the same direction
• Example of dc is a battery
• Alternating current (ac) occurs when
the voltage source alternates in
polarity
• Example of ac is home electrical
wiring
• ac in mathematical terms is describes
a sine wave
• sine wave period - length of time it
takes to complete one cycle in a
second
• sine wave frequency – number of
cycles per second
Community College of Rhode Island
8
Energy
• The basic unit (measurement) of power is the watt
(W), named after James Watt (1736–1819), who also
invented the steam engine
• Voltage by itself does not do any real work. Current
by itself does not do any real work.
• However, voltage and current together can produce
real work.
• The product of voltage times current is power.
• Power is used to produce real work
• Power is only produced when current flows through
a load
Community College of Rhode Island
9/6/2016
• Frequency is the term used to describe the number
of cycles in a second-hertz (Hz)
• Hz named after Heinrich Hertz (1857–1894), a
German physicist
• frequency is a term used only for ac circuits
• United States, the standard frequency is 60
cycles/second or 60 hertz (Hz)
• European countries have adopted 50 hertz (Hz)
• Countries outside the United States and Europe use
50 and/or 60 hertz
• Direct current (dc) has no frequency
9/6/2016
11
Community College of Rhode Island
9/6/2016
12
2
9/6/2016
Comparing ac and dc Voltage and Current
Electric Voltage and Current Relationships
• dc Power Source
• Continuously supplies
power
• Equivalent heating =
dc voltage x current
• Voltage step-up and stepdown is complex (inverter is
needed)
• dc power transmission is
cost effective over three
hundred miles
• Voltage is the source of power
• Current is what flows in a load and electric circuit
Current
Load
Voltage Source
Community College of Rhode Island
9/6/2016
13
Community College of Rhode Island
9/6/2016
14
Real and Reactive Power
Three Types of Electrical Loads
• Real and reactive power must be considered with
inductive or capacitive loads
• Total Power = Real power + Reactive power
• Real power (watts) – does useful work
• Reactive power (VAR) – extra cost
• Motors are an example of the need to consider
reactive power (+ VAR)
• Reactive power increases the cost of power
transmission
• Capacitors (- VAR) are used to offset inductive
reactive power
• Resistive loads- current
flow produces heat –
resistance (ohms)
• Inductive loads – current
lags voltage – (henrys)
• Capacitive loads – current
leads voltage –(farads)
Community College of Rhode Island
9/6/2016
15
Bulk Energy Generation
Community College of Rhode Island
9/6/2016
16
Energy Distribution
• Non-Renewable: Non-Variable
• Distribution of Bulk
• Distribution of Storage
• Capacitor Bank
Distribution
• Control, Measure,
Protection
• Record and Optimization
– Nuclear
– Coal
– Gas
• Renewable : Non-Variable
–
–
–
–
• ac Power Source
• Increase and decreases
power
• Equivalent heating =
rms voltage x rms current
(rms = root mean squared)
• Voltage step-up and stepdown is easy with
transformer
• Most power transmission
today is ac
Hydro
Biomass
Geothermal
Pump Storage
• Renewable: Variable
– Wind
– Solar
Source: IEEE
Source: IEEE
Community College of Rhode Island
9/6/2016
17
3
9/6/2016
Energy Customers
Energy Operations
•
•
•
•
•
Residential
Commercial
Industrial
Smart meters
Two-way
communications
• Customer
generation
• Energy Domains
• Domain Flow Control
• Substation two-way
communications
• Monitoring and
reporting control
• Customer network
data gathering and
control
Source: IEEE
Source: IEEE
Electrical Power is Low Tech to High Tech
Power Engineering Components
•
•
•
•
•
•
•
Community College of Rhode Island
9/6/2016
Sensors and Measurement
Generators
Transmission lines
Transformers
Switches
Capacitors
Current Protection
Sensors
21
Sine Wave Voltage
Effective voltage of the AC power system is 0.707 times the peak voltage.
Peak voltage is about 170 volts. Thus the 120 volts is really an effective
voltage. Effective voltage is sometimes known as the rms (root mean square)
voltage.
•
•
•
•
•
•
Electric Current
Voltage
Power
Voltage-Current Phase angle (Power Factor)
Temperature
Harmonics
Community College of Rhode Island
9/6/2016
24
4
9/6/2016
Reasons for Alternating Current
Waveforms
• Electromechanical generators produce alternating
current
• Less energy loss in transmission lines if power (P) is
transmitted at higher voltages (V) and lower current(I).
Lower current yields less power loss (Pl).
• P=IxV
• Pl = I2 x R (R = resistance in transmission line).
• Voltage can be altered by transformers only for AC. For
example to lower transmission voltages (e.g.,345Kv) to
120 v for household use.
Community College of Rhode Island
9/6/2016
Converting DC to AC
Simple inverter (top = mechanical switch,
bottom = transistor switch)
25
Community College of Rhode Island
9/6/2016
26
Converting AC to DC
Half-wave rectifier:
Capacitor and Inductor Filter
Full- wave rectifier
• Using capacitors and inductors we can level the
voltage output of a rectifier
• A capacitor opposes changes in voltage
• An inductor opposes changes in current
Community College of Rhode Island
9/6/2016
30
5
9/6/2016
How Power Grids Work
Generator Utilization
http://www.loc.gov/rr/business/hottopic/electricpower.html
60
88%
50
74%
40
59%
30
44%
20
29%
10
15%
0
10:15 AM
Capacity Utilized
Power Used (kW)
Average Generator Capacity Utilization over a Day
0%
4:15 PM
Community College of Rhode Island
10:15 PM
4:15 AM
10:15 AM
9/6/2016
31
6