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The Transmission of Electric Energy

The Transmission of Electric Energy. ET2105 Electrical Power System Essentials. Prof. Lou van der Sluis. Introduction (1). Transmission and Distribution Advantages of interconnected systems Better reliability Smaller frequency deviations Better overall system efficiency

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The Transmission of Electric Energy

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  1. The Transmission of Electric Energy ET2105 Electrical Power System Essentials Prof. Lou van der Sluis Electrical Power System Essentials

  2. Introduction (1) • Transmission and Distribution • Advantages of interconnected systems • Better reliability • Smaller frequency deviations • Better overall system efficiency • Facilitates power exchange • Disadvantages of interconnected systems • Limitations to interconnection transport capacity • Power losses because of energy exchange • Unwanted parallel power flows • More complex system operation Electrical Power System Essentials

  3. Introduction (2) Rated voltage for AC – power system Electrical Power System Essentials

  4. Introduction (3) Voltage levels in the Dutch Power System Electrical Power System Essentials

  5. Introduction (4) The Dutch High-Voltage Network Electrical Power System Essentials

  6. Network Structures Radial structure Loop structure Multi-loop structure Electrical Power System Essentials

  7. Substations (1) Open-air substation Courtesy of TenneT TSO B.V. Electrical Power System Essentials

  8. Substations (2) High-Voltage Circuit Breakers and Pantograph Disconnector Courtesy of TenneT TSO B.V. Electrical Power System Essentials

  9. Substations (3) SF6-insulated substation Courtesy of Eaton Holec Electrical Power System Essentials

  10. Substations (4) Bus system Single bus system Double bus system Electrical Power System Essentials

  11. The Transformer The ideal transformer Electrical Power System Essentials

  12. The Transformer Model (1) • Not ideal • Permeability is not infinity • Finite self inductance • Leakage flux • Winding losses (copper losses) • Core losses • Hysteresis • Eddy-current losses Electrical Power System Essentials

  13. The Transformer Model (2) Copper losses Leakage reactance Iron losses (core) Magnetizing susceptance Efficiency = Pout / Pin = 1 – Ploss / Pin Electrical Power System Essentials

  14. Three-Phase Transformer (1) • Three single-phase transformers • Three phase transformer • Complex turns ratio 1 : a*ej • Amplitude • Phase shift: multiple of 30° Electrical Power System Essentials

  15. Three-Phase Transformer (2) Single-phase equivalent Electrical Power System Essentials

  16. Three-Phase Transformer (3) Out of the tank Courtesy of TenneT TSO B.V. Electrical Power System Essentials

  17. The Yy-4 Transformer Electrical Power System Essentials

  18. The Yd-11 Transformer Electrical Power System Essentials

  19. The Magnetization Current The magnetization current contains a third harmonic Electrical Power System Essentials

  20. Overhead Transmission Lines (1) 380 kV River crossing Courtesy of TenneT TSO B.V. Electrical Power System Essentials

  21. Overhead Transmission Lines (2) The power carriers in the Dutch power system Electrical Power System Essentials

  22. Overhead Transmission Lines (3) 150kV transmission line tower Electrical Power System Essentials

  23. Transmission Line Conductors (1) • Material • Al • Cu • ACSR (Aluminum Conductor Steel Reinforced) Electrical Power System Essentials

  24. Transmission Line Conductors (2) Courtesy of TenneT TSO B.V. Electrical Power System Essentials

  25. Transmission Line Conductors (3) Advantages and disadvantages of bundled conductors Electrical Power System Essentials

  26. Galloping Lines • Counter measures Electrical Power System Essentials

  27. Shield Wires Electrical Power System Essentials

  28. Transposition (1) • Unbalanced system • Solution: transposition Electrical Power System Essentials

  29. Transposition (2) Electrical Power System Essentials

  30. High-Voltage Cable • 6/10 kV cable • 220/380 kV cable Courtesy of Prysmian Cable Holding B.V. Electrical Power System Essentials

  31. Transmission of Power E H S S H E S E H V S S E H S S H E Poynting Vector: S = E x H Electrical Power System Essentials

  32. Conductor Modeling L R G C • L : H-field • C : E-field • R : Ohmic losses • G : Insulator and corona losses Electrical Power System Essentials

  33. Line / Cable • Line, 150 kV • R = 0.125/km • XL = 0.425 /km • C = 7.7 nF/km • Sth = 130 MVA • Cable, 150 kV • R = 0.12 /km • XL = 0.166 /km • C = 210nF/km • Sth = 135 MVA Electrical Power System Essentials

  34. 1 km Line / Cable • Line, 132 kV • R = 0.178  • XL = j0.40  • XC = -j350 k • I = 450 A • Cable, 400 kV • R = 9 m • L = 0.4 mH • C = 0.38 µF • I = 1.9 kA Electrical Power System Essentials

  35. Line Models Z IS IR VS VR Z IS IR VS Y/2 Y/2 VR IS IR /km H/km F/km VS VR • Short (<80 km) • Medium (80 km..240 km) • Long (>240 km) Electrical Power System Essentials

  36. Short Line R+jX IS IR VS VR Vs Vs jIrX jIrX Vs Ir jIrX IrR Vr Vr Vr Ir IrR IrR Ir Electrical Power System Essentials

  37. Series-Compensation Hydro-Quebec / 735 kV • Z = R + jX = R + j (L - 1/C) Electrical Power System Essentials

  38. Long Line: Distributed Elements I(x+x) zx I(x) yx V(x) V(x+x) x Electrical Power System Essentials

  39. Equivalent Circuits of Lines IS Z IR VS VR IS Z IR VS VR Y/2 Y/2 IS Z' IR VS VR Y'/2 Y'/2 • Short • Medium • Long Electrical Power System Essentials

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