The relationship between percent and per unit impedance

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SUMMARY

The relationship between percent impedance and per unit impedance is critical in electrical engineering, particularly in transformer analysis. Percent impedance (x%) is determined by short-circuiting the secondary windings and increasing voltage until the desired full load current is achieved. The per unit (p.u) system converts this percentage into a numerical format, simplifying calculations in complex circuits. Understanding these concepts is essential for effective analysis in applications such as national power grid studies.

PREREQUISITES
  • Transformer short-circuit testing
  • Understanding of percent impedance
  • Familiarity with per unit system calculations
  • Basic electrical circuit analysis
NEXT STEPS
  • Study transformer short-circuit testing methods
  • Learn about the per unit system and its applications in power systems
  • Research impedance calculations in complex electrical circuits
  • Explore case studies on national power grid analysis using per unit bases
USEFUL FOR

Electrical engineering students, power system analysts, and professionals involved in transformer design and national grid studies will benefit from this discussion.

Callum Plunkett
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Homework Statement


For one of my assignments I’ve been ask about the relationship between percent impedance and per unit impedance.

Homework Equations

The Attempt at a Solution


I know that the x% is determined in transformers by short circuiting the secondary windings and slowly increasing the voltage until the secondary gives the desired full load current. And that x p.u is the x % converted into number form which has the advantage of simplifying calculations on more complex circuits. But other than that I’m unsure if there is anything else I can add to my answer. Can anyone point me in the right direction?
 
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If you were doing a study of the national power grid, how would you choose a per unit base for the study?
 

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