Per-unit & three-phase
Common bases that make every voltage level comparable, plus three-phase fundamentals.
Lessons
Lesson 1
Per-unit system + base conversion
Why expressing every quantity as a fraction of a base makes power-system math beautiful — and how to convert between bases without panic.
Lesson 2
Symmetrical components — Fortescue decomposition
Any three unbalanced phasors split uniquely into a balanced positive-sequence + a balanced negative-sequence + a zero-sequence set. The algebra behind all unbalanced fault analysis.
Lesson 3
Three-phase circuit analysis — Y, Δ, and the power triangle
Line vs phase, Y ↔ Δ conversion, P = √3·V_LL·I_L·cos θ, complex power S = V·I*, and PF correction with capacitors.