Electric System

Carlos SilvaOctober 28st 2009

Electric System Components

Generation

Transmission Network

Substations

Distribution Network

Substations / Transformers

Homes / Industry

ELECTRICITY GENERATION

Transforming energy to electricity

Power PlantTransforms 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

GeneratorsTransforms circular motion of the rotor into electricity

Electricity Generation

France (>2000)USA (>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)

Thermal Power Plant diagram

Taichung (4,7GW)

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%

Castelo Bode (140MW)

Hydro Plant diagram

Itaipu (14GW)

Alqueva(240MW)

Alto Lindoso (632MW)

Wind Power Plant

Wind turbine power: 1 - 5MWMagLev: 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 DiagramWind Potential Europe

Wave Generator

TurbineUsing air flow created by waves to move a turbine

Using wave to push water upwards and using a normal hydro power plant

Hydraulic motorTransforming linear to circular motion

Archimedes (AWS)

Pico,Açores

Pelamis Generator

Linear motion into circular motionCylinders (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

Serpa (11MW)

PV panel power: 150 W/m2

PV plant power: 10 – 60MWMoura (62MW)

PV panel efficiency: 20%

Insolation: 4-7 kW/m2/day

Area: 1MW/hectare

Moura (62MW)

Insolation yearPlant diagram

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)

First light bulb

Thomas Edison

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 SubstationHigh way of electricity

Long distance connections

Usually takes place above 110kV

Overhead lines or underground linesUnderground 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)

São Miguel load curve

Residential Consumption Portugal (DGEG -2004)

Family with four persons