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Electric System
Carlos Silva
October 28st 2009
Electric System Components
Generation
Transmission Network
Substations
Distribution Network
Substations / Transformers
Homes / Industry
ELECTRICITY GENERATION
Transforming energy to electricity
Power Plant
Transforms some type of energy to electric energy
• Circular motion from direct force (hydro, wind, waves)
• Circulation motion from direct steam using heating (thermal, nuclear)
• Photovoltaic panel
Generators
Transforms circular motion of the rotor into electricity
Electricity Generation
USA (>2000)
France (>2000)
Portugal (2006)
Thermal Power Plants
Power: 200 to 500 MW
Efficiency: 33% to 48%
Fuel: coal, natural gas, nuclear, oil, solar
Sines (1,2GW)
Taichung (4,7GW)
Thermal Power Plant diagram
Geothermal Power Plant
Ribeira Grande power: 14 MW
Efficiency: <80%
Ribeira Grande
(14MW)
Geothermal Diagram
Geothermal Power Plant
Ribeira Grande power: 14 MW
Efficiency: <40%
Ribeira Grande
(14MW)
Geothermal Diagram
Hydro Power Plants
Power: 100 MW to 14GW
Efficiency: 90%
Hydro Plant diagram
Castelo Bode
(140MW)
Alqueva
(240MW)
Alto Lindoso
(632MW)
Itaipu
(14GW)
Wind Power Plant
Wind turbine power: 1 - 5MW
MagLev: 1GW(?)
Wind farm power: 10 – 300MW
Betz efficiency: 59.6%
Wind turbine efficiency: 30%
Capacity factor: 20 - 40%
Area: 5MW /hectare
Copenhagen
(40MW)
Pampilhosa
(81MW)
Wind Turbine Diagram
Wind Potential Europe
Wave Generator
Turbine
Using air flow created by waves to move a turbine
Using wave to push water upwards and using a normal hydro power plant
Hydraulic motor
Transforming linear to circular motion
Pico,
Açores
Archimedes
(AWS)
Pelamis Generator
Linear motion into circular motion
Cylinders (linear) and hydraulic motor( circular)
Wave Power Plant
Pelamis power: 0.75 MW
Wave farm power: 2 – 20MW
Efficiency: 25-40%
Area: 30kW/ hectare
Wave world potential
PovoaVarzim
(2,25MW)
Photovoltaic Power Plant
PV panel power: 150 W/m2
PV plant power: 10 – 60MW
Moura (62MW)
PV panel efficiency: 20%
Insolation: 4-7 kW/m2/day
Area: 1MW/hectare
Serpa (11MW)
Moura (62MW)
Plant diagram
Insolation year
ELECTRICITY TRANSMISSION
First commercial electric system (US)
First distribution systems were DC (Thomas
Edison)
Electric load was essentially incandescent lamps
(100V DC)
• Other systems (motors) required other voltages
DC could be used wit storage batteries (used as
backup)
DC generators (110V) could be used in parallel to
increase production capacity
• DC generators had to be within 2.4km (1.5mile)
from users
• Different voltages required different generators
Edison had invented an electric meter (DC)
Thomas Edison
First light bulb
Tesla invents the AC electric system
AC shows up on 1880 (George Westinghouse)
AC could be generated with higher efficiencies
AC could be transmitted over larger distances
• It was easier to increase and decrease
voltages (transformation)
Risks were similar
Nikola Tesla
George Westinghouse
War of currents
Edison makes a negative campaign
AC was more danger
Harold P. Brown, Edison’s employee, developed the first electric chair (AC)
Niagara Falls Commission contract (1893)
Edison + General Electric lost against George Westinghouse + Tesla
1896 generation started to Buffalo industries
AC became the standard on 1900
Helsinki had a DC system until 1940
Boston, Massachusetts had DC systems until 1960
1998, Consolidated Edison (New York) started eliminating remaining systems (2007)
DC is still used for transmission (HVDC)
Transmission
Between Power Plant and Substation
High way of electricity
Long distance connections
Usually takes place above 110kV
Overhead lines or underground lines
Underground lines costs are 10 to 20 times
higher
Maintenance in underground lines is much
more expensive
Difficulties in voltage management due to
reactive power
Magnetic field range is smaller
Losses
Losses are due to Joule heating
Electric energy transformed into thermal
energy (incandescent lamps)
These losses are proportional to current
and wire resistance
For the same power, higher voltages
means less current
Transporting energy in higher voltage
decreases losses
They usually represent between 5 to 10%
of transmitted power
Power Station
Decrease very high voltage to
high voltage (60kV, 30KV)
Transformers
Two coils with different number of
spirals
HVDC systems
High Voltage Direct Current
Develop din Sweden in 1930’s
Less infrastructure costs
Less transmission losses
Used for very long distances
Inga-Kolwesi connecting Inga-Dam and
cooper mining in Katanga (1700km)
Used to connect different AC systems
Brazil (60Hz) and Paraguay(50Hz) electricity
produced at ITAIPU
Undersea cables
Interconnection between Philippines
between islands produced by geothermic
Inga-Kolwesi
ELECTRICITY DISTRIBUTION
Distribution
Between power stations and homes
Reduce 60kV/30KV to 15, 10, 5KV
Distribution pole
High Voltage (60kV) Grid - Lisbon
Load Curve
Amount of electricity requested by customers
The amount of produced electricity has to be equal to the demand
Hard to obtain when the production is variable (renewables)
A typical evolution day from 2007 to 2013
100000
90000
80000
60000
Fuel
50000
Geothermal
40000
Hydro
Consumption
30000
20000
10000
0
1…
7
13
19
1…
7
13
19
1…
7
13
19
1…
7
13
19
1…
7
13
19
1…
7
13
19
1…
7
13
19
kW
70000
São Miguel load curve
Residential Consumption Portugal (DGEG -2004)
Family with four persons