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9. Protection

NCEES Topic 9 (10–15 questions). Overcurrent, protective relaying, protective devices, coordination.

Chapters

Chapter

A. Overcurrent protection

Overcurrent coordination — 50/51 phase + 50N/51N ground, TCC curves, CTI margins.

1 lesson
Chapter

B. Protective relaying

Differential (87) + distance (21) + zone protection for transformers, motors, generators, lines, buses.

6 lessons
Chapter

C. Protective devices (fuses, breakers, reclosers)

Switchgear + breaker ratings + interrupting capacity, breaker-failure backup + auto-reclosing schemes.

2 lessons