Glossary

Acceptance criterion — A predefined quantitative or logical condition that a run, model, case, or comparison must satisfy before it is accepted.

Algebraic state — A variable solved from instantaneous constraints rather than integrated through time.

Average-value model — A converter representation that averages switching behavior over a carrier interval and omits explicit semiconductor commutations.

Base quantity — Reference voltage, current, power, impedance, speed, or other value used to interpret a per-unit quantity.

BCTRAN-style model — A transformer terminal representation based on test-derived multiwinding matrices. The term describes a modeling style, not certification against another product.

Bergeron model — A travelling-wave line representation using characteristic impedance/admittance and delayed terminal history.

Capability descriptor — Typed record identifying a study, domain, maturity, and source owner.

Case — A reproducible engineering example containing purpose, input, entrypoint, output contract, interpretation, and acceptance evidence.

Checkpoint — Serialized execution state sufficient to resume a run under a compatible model/solver/schema contract.

Companion model — A discrete-time equivalent of a dynamic component, typically represented by an instantaneous conductance/admittance plus history source.

Constitutive law — Mathematical relationship between physical quantities of a component, such as nonlinear current as a function of voltage.

Control calendar — Exact release schedule for sensing, estimation, control, modulation, protection, or reporting tasks.

Deck — Text input containing typed or classic fixed-field cards that define a study, topology, models, events, and outputs.

Delayed history — Stored past values required by travelling-wave, rational, sampled, or delayed-control models.

Deterministic replay — Re-execution that produces the same declared result according to a bitwise or tolerance-based contract.

Direct feedthrough — Output dependence on an input at the same logical instant, important for algebraic-loop analysis.

EMT — Electromagnetic transient time-domain study resolving instantaneous electrical quantities and fast events.

Event localization — Determination of the actual discontinuity time between or on integration steps.

Fidelity — Level and kind of physical/numerical detail represented by a model.

Fixed-field card — Input record whose meaning depends on exact character-column positions.

Flux linkage — Magnetic flux linked with a winding, often a dynamic state in machine/transformer models.

Ground return — Frequency-dependent current-return behavior through earth included in line/cable impedance calculations.

Grey-box model — Model combining known physical structure with identified parameters.

History source — Equivalent source representing accumulated dynamic state in a companion formulation.

Implemented — Maturity status indicating a callable study path exists for a declared validity domain.

KCL residual — Numerical imbalance of currents at a solved node according to Kirchhoff’s current law.

Legacy reference — Historical implementation or evidence retained for comparison, not the production execution path.

Modal transformation — Mapping between phase/conductor quantities and decoupled or approximately decoupled modal quantities.

Model contract — Stable statement of inputs, outputs, state, validity, assumptions, maturity, update order, and evidence.

Multi-mass shaft — Mechanical model with multiple inertias connected by stiffness and damping.

Multirate task — Task executing on its own exact sample/release calendar while coupled to the electrical simulation.

Nodal assembly — Construction of network equations from model contributions and source/history injections.

Not implemented — Typed result status for a declared study that lacks a production numerical path.

Passivity — Property that a model cannot generate net energy internally under its declared port convention.

Passivity correction — Transformation of a fitted model to remove passive-behavior violations while controlling approximation error.

Per unit (pu) — Normalized quantity divided by a declared base.

Phase domain — Representation directly in physical phase/conductor coordinates rather than sequence or modal coordinates.

Planned — Maturity status for a roadmap/API descriptor without a production implementation.

Pole/residue model — Rational representation expressed through poles and residues, often converted to state space for runtime.

Positive-real — Frequency-domain property related to passivity for impedance/admittance models under appropriate assumptions.

Prototype — Experimental capability whose interface, behavior, or qualification may change.

Provenance — Traceable source, transformation, uncertainty, and revision of engineering data or evidence.

Rational fitting — Approximation of sampled frequency behavior by stable rational functions.

Reference-compatible case — Case that can run through a declared historical/reference path for comparison; this does not make the reference the production solver.

Result contract — Stable definition of status, quantities, units, assumptions, warnings, metadata, and acceptance evidence.

Rollback — Restoration of all mutated execution state after rejected work or event localization.

Sequence component — Positive-, negative-, or zero-sequence quantity derived through a specified transformation.

Solver backend — Numerical implementation registered behind the public scientific model/study contract.

Source owner — Logical source unit responsible for a model, study, parser, or interface declaration.

State-space realization — Dynamic representation using state, input, output, and feedthrough matrices.

Study descriptor — Typed catalog entry with ID, name, domain, maturity, and source owner.

Surge impedance — Characteristic voltage/current ratio of a travelling-wave mode or line under the declared convention.

TACS — Control-system style algebraic/dynamic signal composition used with electrical simulation.

Task release — Exact instant when a sampled/multirate task executes.

Terminal order — Documented ordering of ports, windings, phases, or conductors in vectors and matrices.

Thevenin equivalent — Ideal voltage source behind finite impedance representing a network boundary.

Topology event — Change in electrical connectivity caused by a switch, fault, breaker, or controlled device.

Typed quantity — Value accompanied by a stable key, unit, optional base, and description.

Validity domain — Declared physical/numerical/fidelity bounds within which a model is supported.

Vector fitting — Iterative method for fitting rational functions to sampled frequency responses.

White-box model — Model derived primarily from detailed geometry, materials, and internal physical structure.

Wideband model — Frequency-dependent dynamic model intended to reproduce behavior over a broad declared frequency range.