Electric power system
- 1. ELEMENTS OF THE POWER SYSTEM Submitted To Mr. Shahbaz Pervez Submitted By Bilal Aslam 03F -EE-17 Salman Tahir 03F-EE-55
- 2. POWER SYSTEM The electrical power system provides a means of generating , transmitting and distributing energy in the form of electric current, to the ultimate users, the load . Generation , Transmission , Distribution and Load form the four basic elements or subsystems of a power system
- 3. SUBSYSTEMS
- 4. GENERATION Generation is simply the conversion of energy from one form to another. The three major types of generation are: FOSSIL HYDRO NUCLEAR
- 5. FOSSIL Fossil fuels such as coal, oil and gas are burned to generate electricity The machines used in fossil generation are high speed but slow starting The main issues are environmental as burning of fuel causes pollution therefore low sulphur content fuel is used
- 6. HYDRO In hydro plants, electric power is generated by the water flowing through a turbine which is coupled solidly to a generator Hydral machines are slow machines but they are quick starting and have a good ramping rate
- 7. NUCLEAR In nuclear plants the basic cycle is similar to that of fossil plant but the required heat is provided by the nuclear reaction rather from burning fuels Due to the stringent government requirements about the safety of nuclear plants, their design and operation are much more complicated than the fossil or hydro units
- 8. TRANSMISSION The transmission system consists of a network of overhead lines or in densely populated areas, under ground cables The lines are designed to transmit large amounts of power from point of generation to the load area
- 9. CLASSIFICATION OF TRANSMISSION LINES We classify transmission lines with reference to: Voltage Distance A.C or DC
- 10. VOLTAGE Ultra high voltage transmission lines(1000 KV) Extra high voltage transmission lines(745 KV) High voltage transmission lines(200 KV) Medium voltage transmission line(132 KV)
- 11. DISTANCE Long length T.L (> 150 KM ) Medium length T.L (50-150 KM) Short length T.L (<50 KM )
- 12. A.C OR D.C The transmission line may be ac or dc depending upon the application
- 13. TYPES OF POWER TRANSMISSION The two general types of power transmission are : Overhead lines Underground cables
- 14. OVERHEAD LINES Overhead lines are of two types AC line DC line
- 15. AC LINES The overhead ac lines are applied on power systems at voltages in the range of 115 KV to 800 KV
- 16. COMPONENTS OF A TRANSMISSION LINE Conductors Ground wires Insulators Towers
- 17. Conductors are either solid round,stranded or bundled. Stranding provides flexibility The Ground wire acts as a shield to protect the energized conductors from lightning strokes Insulators suspend the energized phase conductors and insulate them from grounded tower The Tower support the conductors and is the most visual part of a T.L
- 18. DC TRANSMISSION LINE In this mode of transmission, the three phase, 60 Hz voltages and currents are converted to dc, transmitted on a dc line and are converted back to ac at the other end
- 19. USES OF THE DC TRANSMISSION LINE To connect two systems operating at different frequencies For long underground or under water transmission For long distance overhead transmission
- 20. DC lines are sometimes called asynchronous ties since they can be used to inter connect two systems operating at different frequencies Moreover DC transmission is chosen over AC because it is less expensive than AC over very long distances
- 21. CABLES Underground cables are used in very densely populated areas but they are rarely used because they are more expensive as they require insulating materials instead of air to separate the conductors from each other and from ground
- 22. DISADVANTAGES OF CABLES There are also some technical disadvantages associated with underground cables. One major problem is the very high capacitance inherent in the underground cables. This capacitance give rise to charging currents. Special equipments must be installed to compensate for the effect of charging currents, which adds to the cost
- 23. TYPES OF CABLES OIL FILLED PIPE TYPE CABLE OIL FILLED SELF CONTAINED CABLE SOLID DIELECTRIC CABLE SF6 CABLE
- 24. DISTRIBUTION The distribution system consists of a network overhead lines and underground cables by which the power is distributed to the ultimate users of electricity that is the load
- 25. LOAD The utilization of electric power is collectively called load . This includes the uses of electricity in homes, factories, offices and for recreation, entertainment, etc
- 26. SYSTEM VOLTAGES Generation voltages are in the range of 12-35KV Transmission voltages are in the range of 115-800 KV. Distribution voltages are in the range of 4-35 KV. Loads operate at variety of voltages due to their diverse nature
- 27. POWER IS TRANSMITTED AT HIGH VOLTAGE RATHER HIGH CURRENT
- 28. Power transmitted is directly proportional to product of V and I but losses are directly proportional to I 2 , therefore to transmit power with minimum loss we use high voltage