N-1 Contingency Analysis

Automatically remove each branch in the one-line model and check for voltage violations and branch overloads.

Method & Assumptions

For each branch (cable, transformer, or tie) in the one-line diagram, the branch is removed and a Newton–Raphson load flow is re-solved. Violations are flagged when:

  • Bus voltage departs from the configured per-unit bounds (default 0.95–1.05 pu)
  • A branch loading exceeds the configurable threshold (default 100% of rating)
  • The modified network fails to converge (indicates an island or severe overload)

When "Check rotor angle stability" is enabled, a classical one-machine infinite-bus (OMIB) swing equation is solved for each generator-connected bus. Pre-fault and post-fault maximum power transfer are estimated from the 30° operating-angle assumption and the post-contingency voltage ratio. If the rotor angle exceeds 180° before re-synchronisation, the contingency is flagged as transient instability.

Results are stored in the project's Studies object and can be referenced by other tools.

Prerequisites: Define buses and branches in the One-Line Diagram editor and run a base-case Load Flow study first.

Study Parameters

System base power in MVA (typically 100). Lower voltage threshold in per-unit (default 0.95). Upper voltage threshold in per-unit (default 1.05). Branch loading percentage above which a violation is flagged (default 100%).
Transient Stability (optional) Requires generator buses (Pg > 0) in the one-line model. Machine inertia constant. Typical: 2–4 s (gas turbine), 4–6 s (steam), 6–10 s (hydro). Primary protection clearing time (default 0.1 s = 6-cycle at 60 Hz).

Results

Branch Removed Type Converged Violations Status Transient Stability
Run the study to see results.