1 / 38

Generating Electricity

Generating Electricity. COMBINED-CYCLE PLANT. Combined heat and power – fuller utilization of heat. Appropriate in high density places Don’t “add” efficiencies. Calculate utilization , ε :. Energy conversion. Thermal energy converted to motion using turbine

tryna
Télécharger la présentation

Generating Electricity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Generating Electricity

  2. COMBINED-CYCLE PLANT

  3. Combined heat and power – fuller utilization of heat • Appropriate in high density places • Don’t “add” efficiencies. Calculate utilization, ε :

  4. Energy conversion • Thermal energy converted to motion using turbine • Steam – Steam-Turbine-Generator • Combustion gases – Gas-Turbine-Generator • Turbine subject to device efficiency and Carnot efficiency • Motion of turbine blades • Rotates the shaft of electric generator • Converts the rotational energy into electricity

  5. Faraday’s law where |e| is the “electromotive force” (“emf” is also what we call “Voltage”) Easy way to get df/dt: Move conductor through magnetic field (or move mag. field)

  6. Flux linkages and Faraday’s Law If magnetic flux links an N turn coil Where V is the voltage and l is the flux linkage If all flux links all turns then l=Nf

  7. Mnagnetic cores To ensure all magnetic flux flows through coils we employ “magnetic core” • High magnetic permeability material • Guide magnetic fields through electrical devices • Usually made of ferromagnetic metal such as iron (steel)

  8. Relative Permeability

  9. Simple generator

  10. Multiple pole generator • The following figure shows a 2-pole and a 4-pole synchronous generator

  11. Magnetic Excitation Rotor is electromagnet, contains “field windings”

  12. Rotation Speed The frequency of generated voltage in U.S. is 60 Hz • Europe, Japan = 50Hz Therefore, the shaft of generator must turn at a certain speed: NS is called the synchronous speed

  13. Increasing number of poles Increasing number of poles increases number of times magnetic flux changes per revolution of the rotor. Synchronous spped depends on number of poles (p) and output frequency (f) Allows shaft to turn slower (easier to build/maintain)

  14. Generating three phase power Three voltage sources with equal magnitude, but with an angle shift of 120

  15. Advantages of 3 Power Can transmit more power for same amount of wire (twice as much as single phase) Torque produced by 3 machines is constant Three phase machines use less material for same power rating Three phase machines start more easily than single phase machines

  16. Balanced 3 Phase (3) Systems 3 phase system has equal loads on each phase equal impedance on the lines connecting the generators to the loads Bulk power systems almost exclusively 3 Single phase is used in low voltage, low power settings (e.g., residential, light commercial)

  17. Three Phase Transmission Line

  18. Power transmission • Generation: 2.3 to 30 kV

  19. Electric Grid

  20. US Electrical System

  21. Actual System Interconnections

  22. TRANSMISSION GRID • The following figure shows the one-line diagram of an HVDC link

  23. TRANSMISSION LINES • The following figure shows the tower configurations

  24. TRANSMISSION LINES

  25. TRANSMISSION & DISTRIBUTION

  26. Frequency Control Steady-state operation only occurs when the total generation exactly matches the total load plus the total losses too much generation causes the system frequency to increase too little generation causes the system frequency to decrease (e.g., loss of a generator) AGC is used to control system frequency

  27. April 23, 2002 Frequency Response Following Loss of 2600 MW

  28. Power transmission Generation: 2.3 to 30 kV, Transmission: 138 kV to 765 kV (why?)

  29. Transformers Overview Power systems have many different voltages 765 kV down to 240/120 volts. Ability of simple change of voltage levels is the key advantage of AC over DC systems Transformers are used to transfer power between different voltage levels

  30. Transmission Level Transformer 230 kV surge arrestors 115 kV surge arrestors Oil Cooler Radiators W/Fans Oil pump

  31. 115 kV – 35 kV distribution transformer

  32. Ideal Transformer • Let’s examine an ideal transformer • no real power losses • magnetic core has infinite permeability • no leakage flux • Nomenclature I may use: • “primary” side is “power in” • “secondary” is “power out”

  33. Flux linkages and Faraday’s Law If magnetic flux links an N turn coil Where V is the voltage and l is the flux linkage If all flux links all turns then l=Nf

  34. Ideal Transformer: Turns Ratio

  35. Ideal Transformer: Voltage and Current

  36. Residential Distribution Transformers Single phase transformers used in residential distribution systems Most distribution systems are 4 wire, with a multi-grounded, common neutral

More Related