An end-to-end modelling study

Page status: draft capstone workbook over the existing running fixture; no new solved application is claimed.

Your task is to explain and defend a computational model, including one transformation and its recovery checks. Use the existing multiconductor running fixture. Its difficulty is deliberate: it combines conductor connections, grounding, parallel equipment, and a multiwinding transformer. You are now using these features together after studying smaller examples.

Before extending this case, complete one correction from Building and changing a model you can check. Its import, outage-update and multiplier examples show how to choose a discriminating check and state what remains unverified.

1. Declare the study

Read The running multiconductor network and Executable running network. State the operating state, the quantities the study observes, and the decision domain actually solved by the fixture. Distinguish fixed data from optimized variables. List at least one question the fixture does not answer.

Use the existing PF/OPF study as your starting task. Introducing a new contingency, estimator, or protection calculation would require its own model and evidence; those are possible extensions after this exercise.

2. Trace equipment into equations

Choose one line, one grounding relation, and one transformer winding. For each, record its stable identity, ordered terminals, units, and the equations and constraints that use its quantities. Locate its contribution in a generated view. Explain any virtual node or arc encountered along that path.

Draw a small part of the equipment topology and the corresponding matrix support. Identify an adjacency whose meaning changes between those views. Use the source maps supplied with the fixture rather than guessing equipment identity from a matrix entry.

3. Predict a transformation

Choose a transformation already supported by a listed case in the computational guide. State its source, target, applicability guards, joint observations, and recovery map. Predict which constraints need evaluation on recovered quantities.

Do not assume that a transformation tested on a separate small fixture is applicable to the complete running network. Either establish the guards for its chosen subsystem, or keep the small fixture as the transformation study and explicitly record that boundary. A justified rejection is a valid result.

4. Reproduce and recover

Follow the execution command and environment in the associated case chapter. Record the actual software revisions, inputs, solver status where applicable, residuals, and tolerances. Compare source and target observations. Recover the eliminated quantities and evaluate the source constraints that depend on them.

Run the returned-solution verification exercise. Record the four line-current residuals, the package profile's findings, and the reaction to the altered i2.a voltage. Explain which source quantities were recomputed and which data or primitive construction were shared. The full feasibility-evidence gate should return indeterminate; explain the missing all-device equation and nodal KCL evidence instead of converting that refusal into a passing result.

If the case is locally solved, describe it as a local numerical comparison. Use a derivation or a separate bound for any stronger feasible-set or optimality statement. Explain which construction data and algorithms are shared by any independent comparison.

5. Challenge the conclusion

Propose one nearby input change that violates a guard: an internal shunt, a finite grounding impedance, a changed conductor order, or a changed control domain. Predict whether it should cause rejection or require a different rule. Run the corresponding existing negative test where available and record its actual result. Keep a proposed extension distinct from one you have executed.

Submit a short scientific account

Your account should contain the study question; source assumptions and input identity; one diagram; the transformation and recovery equations; a compact comparison of predicted and observed quantities; the failed near-miss; and a precise conclusion. Include the commands needed to reproduce the work.

A satisfactory account allows another reader to identify what was checked, where the original constraints enter, and why the conclusion stops at its stated boundary. A small residual alone is insufficient. If data, applicability, or recovery remain unresolved, explain the missing evidence and the next calculation that would resolve it.

Worked assessment of the verification step

A defensible account reports that the unaltered case satisfies the lesson's line-current and power-balance tolerances, while the altered voltage violates a voltage bound and disagrees with currents recovered from the line primitives. It distinguishes initialization and active-bound warnings from violated constraints. It does not infer global optimality from LOCALLY_SOLVED or call the whole model independently verified. The missing full residual bundle is an explicit conclusion, not a failed exercise.

For a smaller complete decision argument, reproduce the interval model-choice exercise: explain why a 109 A nominally accepted transfer is not robust over the declared conductance interval. Submit the monotonicity argument and recovered member currents. Keep its scalar scope separate from the multiconductor running fixture.