Power Systems Revision Plan for GATE 2026 (EE)

Objective: Build clear concepts, formula fluency, and PYQ-driven accuracy. Target 7–10 days of focused revision, 3–4h/day.

Overall Approach
– Concept → Formula sheet → PYQs (topic-wise) → Short notes → Mixed practice → Mini-mocks.
– Maintain an error log: concept gap, formula slip, unit mistake, approximation error, time trap.

Topic-Wise Revision Flow

1) Per-Unit System + Line Parameters

– Revise: Base change, %impedance conversion, Zpu/Sbase scaling, ABCD intuition.
– Must-know: Short/medium/long line models; skin effect basics; Kelvin’s law idea.
– Practice: 30–40 PYQs.
– Quick checks:
– Convert Z given on MVA base to the new base fast.
– Find VR, efficiency with ABCD quickly for given load and pf.

2) Overhead Lines, Cables, Insulators

– Revise: Sag–tension basics, string efficiency,  corona inception and power loss, grading of cables, and insulation coordination basics.
– Practice: 20–30 PYQs.
– Quick checks:
– Effect of conductor spacing and diameter on corona.
– String efficiency improvement methods (grading, guard rings).

3) Power Flow (Load Flow) Fundamentals

– Revise: Bus types (PQ, PV, Slack), power balance, Jacobian structure, DC load flow approximations.
– Focus: Conceptual questions, small numerical problems with 2–3 bus systems.
– Practice: 20–25 PYQs.
– Quick checks:
– What changes when the PV bus hits reactive limits?
– Fast DC approximations: P≈(δ1−δ2)/X, Q-voltage coupling intuition.

4) Fault Analysis (Symmetrical + Basics of Unbalanced)

Revise: Thevenin seen from fault point, I_fault=E_th/(Z_th+Z_f), %X usage, contributions.
– For unbalanced: Sequence networks basics, series/parallel connections for LG, LL, LLG.
– Practice: 35–45 PYQs.
– Quick checks:
– Per-unit short-circuit MVA formula.
– Sequence network connection patterns from memory.

 5) Voltage Control, Reactive Power, and Economic Operation

– Revise: Tap-changing transformers, shunt/series compensation basics, AVR idea.
– Economic dispatch: Incremental cost λ-method, with/without losses (B-coefficients basics).
– Practice: 20–30 PYQs.
– Quick checks:
– Calculate generator outputs from equal incremental cost quickly.
– Effect of shunt capacitors on power factor and voltage.

6) Power System Stability (Steady-State + Transient Basics)

– Revise: Power-angle equation P=EV/X sin δ; equal-area criterion for sudden load change or fault clearing; swing curve intuition.
– Practice: 20–30 PYQs.
– Quick checks:
– Critical clearing angle/ time setup.
– Small-signal vs transient stability conceptually.

7) Protection and Instrumentation (High-Yield Essentials)

– Revise: CT/PT basics, relay types (overcurrent, distance, differential), zones of protection, pilot protection ideas, Mho vs Reactance vs Impedance characteristics, fuse coordination.
– Practice: 30–40 PYQs.
– Quick checks:
– Characteristic circles on R–X plane.
– Differential protection for transformer inrush (2nd harmonic restraint concept).

7-Day Power Systems Revision Schedule

– Day 1: Per-unit + Line models + ABCD. PYQs 30–40. Formula sheet page 1.
– Day 2: Lines, Cables, Insulators, Corona. PYQs 25–30. Diagram-based quick notes.
– Day 3: Power Flow fundamentals + Economic dispatch. PYQs 35–40.
– Day 4: Symmetrical faults. PYQs 25–30. Speed drills on %X/short-circuit MVA.
– Day 5: Unbalanced faults + Sequence networks. PYQs 20–25.
– Day 6: Stability (equal-area + concepts) + Reactive power control. PYQs 25–30.
– Day 7: Protection (distance, differential, overcurrent). PYQs 30–40. 1 sectional mock (60–90min) + error analysis.

If extending to 10 days:
– Day 8: Mixed topic PYQs (40–60) + formula sprint.
– Day 9: Sectional mock (2h) + deep error analysis + patch weak spots.
– Day 10: Revise entire formula book + 25 mixed problems timed.

How to Practice Efficiently

– PYQ method:
1) Attempt timed (topic-wise).
2) Mark error type.
3) Write the “1-line fix” in notes.
4) Redo the same set after 48–72h.
– Mini-mocks:
– 30–60min mixed Power Systems sets. Focus on accuracy>speed initially.
– Calculation speed:
– Memorise common per-unit conversions, angle–sine approximations for small δ.
– Keep R–X plane sketches handy for distance relay questions.

Formula and Concept Must-Haves

– Per-unit:
– Zpu=Zactual×(Sbase/Vbase^2); new base conversion: Zpu,new=Zpu,old×(Sold/Snew)×(Vnew^2/Vold^2).
– Lines:
– Medium line: nominal-π model; ABCD: V1=AV2+BI2, I1=CV2+DI2; for short line, A≈1, D≈1, C≈0, B≈jX.
– Corona:
– Peek’s formula trends: V0∝mvd×r×δ×ln(D/r) (know variable influence, not full memorization).
– Load flow:
– PV bus Q-limits handling; DC load flow assumptions (flat V, small angles, negligible resistance).
– Faults:
– Short-circuit MVA≈(Base MVA)/Zpu; contributions add at common bus.
– Stability:
– Equal-area areas: accelerating vs decelerating power; Pmax=EV/X.
– Protection:
– Distance relay zones reach; Mho circle passes through origin; differential protection principle.

Put these into a 2–3 page formula book and revise daily.

Common Pitfalls to Avoid

– Mixing bases in per-unit without converting all elements.
– Forgetting angle/sign conventions in ABCD-based VR/efficiency problems.
– Overcomplicating load flow—focus on qualitative behavior and DC approximations.
– Not distinguishing between relay characteristics on R–X plane.
– Ignoring units and base quantities—major source of silly mistakes.

Daily Micro-Drills (10–15 minutes each)

– 3 per-unit conversions (with base change).
– 2 ABCD-based regulation questions.
– 2 short-circuit MVA calculations.
– 1 equal-area sketch decision problem.
– 2 relay characteristic identifications on R–X plane.

Test-Day Strategy for Power Systems Section

– Attempt conceptual and formula-direct questions first.
– For long numeric chains (ABCD/fault/stability), write knowns, pick the shortest path, and approximate sensibly.
– If stuck beyond 90s, mark and move—avoid time sinks.

Stay consistent, track errors ruthlessly, and keep the formula book alive. Power Systems rewards clarity and structured thinking—master the flow, and the marks will follow.

All the best
Sohail Ansari
CEO, Neospark Learning
+91-8292480183