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02 old and-per unit
- 1. Power System Representation using One Line Diagrams
- 2. • One Line Diagram or Single Line Diagram
- 3. One Line Diagram Symbols
- 4. OLD Symbols
- 5. Impedance Diagram from One line diagram
- 6. Four Bus power system One Line Diagram Reactance Diagram
- 7. Admittance Diagram Reactance Diagram Admittance Diagram
- 12. • In power system engineering we are concerned with the analysis of the power system down to the “major loads” and this will mean that the analysis will stop at the distribution system voltages. • Many distributions “feeders” attached to a single bus in a distribution substation are lumped into a single “load”.
- 13. Per unit system • Sbase: “System MVA base” is the same throughout the entire power system (say 100 MVA) • The MVA base is a number used to convert loads, generated power and loss quantities to per unit power quantities.
- 15. •
- 18. Analysis of a power system in per unit: Steps • 1) Convert all three phase bus load MW and MVAR, generator MW and MVAR, to three phase per unit quantities using the 3phase system base. • 2) Convert all actual resistance, inductive and capacitive reactance values to per unit using the Zbase for each particular part of the power system where each r, x etc. is located.
- 19. • 3) Carry out all calculations in per unit, solving for the per unit bus voltage magnitudes and bus phase angles, line currents, and transmission losses. • 4) Convert from per unit back to actual MW, MVAR, MVA, and KV.
- 20. G1 G2 M Line 1 Line 2 Line 3 T1 T2 T3 Section A Section C Section B Section D
- 21. Seven Bus Case: One-line Top Area Cost Left Area Cost Right Area Cost 1 2 3 4 5 6 7 106 MW 168 MW 200 MW 201 MW 110 MW 40 MVR 80 MW 30 MVR 130 MW 40 MVR 40 MW 20 MVR 1.00 PU 1.01 PU 1.04 PU1.04 PU 1.04 PU 0.99 PU1.05 PU 62 MW -61 MW 44 MW -42 MW -31 MW 31 MW 38 MW -37 MW 79 MW -77 MW -32 MW 32 MW -14 MW -39 MW 40 MW -20 MW20 MW 40 MW -40 MW 94 MW 200 MW 0 MVR 200 MW 0 MVR 20 MW -20 MW AGC ON AGC ON AGC ON AGC ON AGC ON 8029 $/MWH 4715 $/MWH4189 $/MWH Case Hourly Cost 16933 $/MWH System has three areas Area left has one bus Area right has one bus Area top has five buses
- 22. Summary • One Line Diagram or Single Line Diagram is a graphical representation of the power system • OLD is the starting point for Power System Analysis • Equivalent circuits are different from OLDs • Power system analysis programs give different techniques to create OLDs