Power system analysis, per unit system help

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SUMMARY

This discussion focuses on power system analysis, specifically the per unit system. Key tasks include drawing the reactance diagram, calculating per unit impedances, and determining the current for bms #1 operating at 30 kV with a base of 100 MVA and 300 kV on the generator side. The equations involved include P = VI and the apparent power formula. A suggestion is made to consider using actual quantities instead of the per unit system for clarity in calculations.

PREREQUISITES
  • Understanding of power system fundamentals
  • Familiarity with reactance diagrams
  • Knowledge of per unit system calculations
  • Proficiency in using power equations such as P = VI
NEXT STEPS
  • Study the process of drawing reactance diagrams in power systems
  • Learn how to calculate per unit impedances effectively
  • Explore the implications of using actual quantities versus the per unit system
  • Investigate the application of tap transformer equations in power analysis
USEFUL FOR

Electrical engineers, power system analysts, and students studying power system operations will benefit from this discussion, particularly those working with per unit systems and reactance diagrams.

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Homework Statement


https://dl.dropboxusercontent.com/u/88040310/powerhw3.png
1. Draw the reactance diagram.
2. Calculate the per unit impedances
3. If bms #1 is operating at 30 kV, find the current
Assume base of 100 MVA, 300 kV on the generator side.

Homework Equations


P = VI
s = p +jq
Apparent power = (reactive power^2 + real power^2)^(1/2)

per phase equations, tap transformer equations

The Attempt at a Solution


Starting it slowly, is this how you draw the reactance diagram?
https://dl.dropboxusercontent.com/u/88040310/hw3xdiagram1.png
 
Last edited by a moderator:
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At the risk of being called a heretic, I suggest that the best thing you can do is abandon the "per unit" system. Work with actual quantities, so that your equations make sense and are dimensionally correct. Per unit is useful only in that for certain system classes, it enables estimates of parameters before the actual values are know. Thereafter, it is simply a confusion factor (and a large one at that!).
 

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