format_version: "0.1"
id: g_bus_coupler_changeover
name: "bus coupler auto-changeover (graphical LD)"
domain: power_substation
language: LD-graphical
source:
  origin: authored
  reference: "Authored for this suite, modeling a two-incomer/bus-coupler auto-changeover scheme"
  license: CC-BY-4.0
properties_file: props.yaml
safety_intent: "The coupler may parallel at most one healthy incomer onto the affected section; all three breakers must never be closed together."
validation_status: validated
variants:
  - file: clean.xml
    expected_verdict: true
    ground_truth:
      method: expert
  - file: bomb.xml
    expected_verdict: false
    violated_properties: [P1]
    ground_truth:
      method: fault-injection
      base_variant: clean.xml
      seeded_defect: "Added a maintenance-key OR-branch that closes the coupler whenever maint is asserted with incomer_a_healthy, regardless of incomer_b's actual breaker state."
      witness: "incomer_a_healthy=1, incomer_b_healthy=1, maint=1 closes incomer_a, incomer_b and coupler together."
features: [contacts, coils]
difficulty: medium
tags: [safety, interlock, security, llb, authored]