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Overview

The REFA Workflow

REFA is structured around a hierarchy of objects. Each layer adds more context until a full project analysis is possible.

Environment         OptionalObjects(Loading, StructureConfig)
    │                   |           |
    ▼                   ▼           |
LineDesign ─────────────┐           |                       
                        ▼           ▼                        
                       Line  ──► Project (Rebuild /       ────────► Analysis
                        ▲           ▲     Reconductoring /
Conductor ──────────────┘           |     VoltageUpgrade /
                                    |     HVDC / Existing)
Economics ──────────────────────────┘

Layer 1 — Input Objects

Environment is an independent object holding attributes needed for all technical calculations. Some other necessary technical attributes are provided through objects (Loading, StructureConfig) or directly as attributes of hierarchically higher objects. Economic attributes are provided in Economics to feed any type of project creation.

Layer 2 — LineDesign & Conductor

LineDesign appends an Environment to its other attributes defining the configuration of the corridor (length, spans, circuits, bundles). The LineDesign is independent of which Conductor will be strung.

Layer 3 — Line

Line pairs a LineDesign with a Conductor. All technical calculations (ampacity, sag, corona, losses, congestion) live here. You can build a Line with the constructor or with the + shorthand:

line = Line(line_design=ld, conductor=c)
line = ld + c          # same result
line = c + ld          # same result

Layer 4 — Project

A project wraps one or more Line objects and an Economics object to produce net-present-value of cost estimates. Five project types are available:

Class Description
Rebuild New conductors and new structures from the start
Reconductoring New conductors on existing structures
VoltageUpgrade Raise operating voltage; replace conductors and possibly structures
HVDC HVDC line; replace conductors and possibly structures
Existing Baseline — current line, no changes

Projects can be constructed in two ways:

project = Rebuild(
    conductor_list=[drake(), cuckoo(), dublin()],
    line_design=ld,
    economics=econ,
    power_mw=400, voltage_kv=230,
)

project = Reconductoring(
    line_list=[ld + drake(), ld + cuckoo()],
    economics=econ,
    power_mw=400, voltage_kv=230,
    structure_remaining_life=25,
)

Layer 5 — Analysis

Analysis takes a list of projects and produces a side-by-side comparison for any cost metric.

refa = Analysis(project_list=[rebuild, recon, vu, hvdc, existing])
refa.total_costs_of_projects(time_horizon=40)

Feasibility Filtering

Before reporting costs, every project automatically filters out lines that fail technical constraints:

  • Ampacity (select_ampacity_feasible=True) — the conductor must carry the target current without exceeding its rated temperature, and the ampacity must not exceed 3× the target current (over-designed lines are excluded).
  • Sag (select_sag_feasible=True) — the maximum sag must not exceed line_design.max_sag_m if set.
  • Corona (select_corona_feasible=True) — the operating voltage must not exceed the corona inception voltage.

Any of these filters can be disabled:

project.select_ampacity_feasible = False
project.select_corona_feasible = False

AC vs. DC

Pass is_hvdc=True to any Line method to use DC-specific equations. The HVDC project sets this automatically for all its internal calculations.