Transcript PowerPresentationTomFergusonx

An Overview of the U.S. Electric Power Grid
Generation Choices, Reliability, Challenges
Tom Ferguson, P.E.
Adjunct Instructor
Dept. of Electrical Engineering
University of Minnesota, Duluth
Presentation to EE 1001
September 15, 2016
Where Electricity Comes From
What Do We Know About This?
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We plug LOADS into it
It has THREE prongs in standard layout
The VOLTAGE is ~115 VAC
The WAVEFORM is sinusoidal
Only 60 Hz (cycles per second) is present
ELECTRONS come from somewhere
It’s almost always “ON”
BUT!
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Limited to 15 AMPS
Europe uses different plug
Voltage varies + 5%
Waveform is usually not “clean”
Harmonics may be present
Electrons come from THOUSANDS of generators
It’s 99.99% reliable (off for 53 minutes/yr)
Nuggets of Knowledge
Nugget #1
Nugget #1:
Electricity in the U.S. is an ELECTROMAGNETIC WAVE
with a
FREQUENCY OF 60 CYCLES PER SECOND,
or
60 hertz (abbreviated 60 Hz)
Nuggets of Knowledge
Nugget #2
A wave’s FREQUENCY and VELOCITY
determine its
WAVELENGTH, λ (lambda)
(the distance between wave crests)
For electricity:
λ=
𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦
𝑣
𝑓
= =
300,000,000 𝑚/𝑠
60 𝐻𝑧
= 5000 km!
(3000 miles)
Basic Electric Power System
Nuggets of Knowledge
Nugget # 3
A simple TRANSFORMER has TWO WINDINGS
wrapped around an IRON CORE
VOLTAGES are TRANSFORMED according to the
TURNS RATIO:
𝑉1
𝑉2
=
𝑛1
𝑛2
Where “n” is the number of turns
High Voltage Transmission
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Long distance carrier of electricity
Connects generators with loads
High voltage reduces current flow (P=V x I)
Reduced current reduces losses (Ploss=I2R)
Transmits energy at essentially speed of light
The Grid Powers Society
• Human behavior repeats itself daily
– Morning routine: lights, hot water, electronics
– Stores open: lights, heating/cooling
– Industry starts: pumps, motors, arc furnaces
• The grid must respond to these loads
– generators must be ready and reliable
– generators must be controllable to match load
• The grid is very dynamic
A Typical Day on the California Grid
1 Megawatt
can power
about 500
homes
Ramps up
by 4500 MW
in 80 minutes
2 p.m.
4 a.m.
Nuggets of Knowledge
Nugget #4
POWER is the product of VOLTAGE and CURRENT
or
Power (W, watts) = Voltage (V, volts) X Current (I, Amperes)
or
P=V*I
One MEGAWATT can supply about 500 homes
Generating Choices
• What types of generation are used?
• Varies across U.S. according to
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availability of fossil fuels
availability of renewable energy sources
water availability
environmental limitations
state policies on renewables and nonrenewable
generation
Power Generation Technologies
2014
Renewables 13%
Includes
• Hydro
• Biomass
• Wind
• Solid Waste
• Geothermal
• Solar PV
• Solar Thermal
Nuclear 20%
Natural Gas 27%
Coal 39%
Source: U.S. Energy Information Administration,
Electric Power Monthly (June 2015). Percentages based on Table 1.1 for 2014 Calender Year.
http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_1_01 Updated 9/2015.
Percentages on an ENERGY basis, not capacity.
Challenges with Wind
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No mechanical energy storage (no inertia)
1 MW of nuclear = 8 to 12 MW of wind
Not dispatchable
Negative correlation
with loads
When loads are greatest
during the mid-day,
wind generation is lowest.
Conversely, wind is highest
when least needed (night).
Nuggets of Knowledge
Nugget #5
• Three Synchronized Regions in U.S.
– Eastern U.S. (east of Rockies)
– Western U.S.
– Texas
• Nugget #5:
All generators in
each region are
synchronized
Putting It All Together
“The Grid” = Generators (about 18,000) + HV Transmission Network
Why Do the Lights Go Out?
– Power plant outages
– Transmission line failures
– Solar storms
– Lightning and high winds
– Animals (squirrels, rodents, snakes)
– Car and train accidents
• The high-voltage transmission system is already very “smart”
• The low-voltage distribution system has
MANY OPPORTUNITIES FOR IMPROVEMENT
• The “smart grid” technologies are best suited to the low-voltage system
Good Luck!